Archive for the ‘Small telescopes’ Category

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Observing report: Deep and dark in Big Bear

October 12, 2015

Big Bear Lake

This past weekend I was up in Big Bear for a few days’ vacation. The proximate reason was the PVAA tour of the Big Bear Solar Observatory on Friday, Oct. 9 – more on that in another post. London and I went up Thursday evening with Steve Sittig, who runs the Hefner Observatory at the Webb Schools here in Claremont. Thursday evening Steve took us out to one of his favorite dark-sky observing sites a few miles east of Big Bear. (I didn’t get any pictures from the observing site, so you’re getting pictures of London and me hiking instead.)

We had hoped to get an early start but a succession of minor things kept us from getting set up and going until about 10:15 PM. By that time astronomical twilight was long over. There was a noticeable light dome from the LA metro area but it only badly affected the last 15-20 degrees above the local horizon, and only in the southwest.

Oh, speaking of the ‘local horizon’ – the site is in a shallow bowl with low hills fairly close on three sides and a bit more distant on the fourth. We could occasionally see lights from vehicles on a bend in the road about a mile off, but other than that, no artificial lights were visible from the site. None. The altitude is around 6700 feet.

The combined effect of this was that the sky was dark right down to the horizon. There was none of the usual near-horizon crud that obscures objects for the first 10 or so degrees after they rise. The seeing was worse near the horizon but the transparency was still excellent. We looked at Orion virtually as soon as it was up, and although we really had to pour on the magnification to split the Trapezium, the nebulosity was already very extensive.

A word about gear. Steve had his ETX 125, a 5-inch f/15 Mak on a motorized base with a hand controller. London had his Orion 20×50 compact spotting scope – I have been regularly kicking myself for not snapping up one of those for myself while they were still available. I had my C80ED refractor on the SkyWatcher AZ4 mount (= Orion VersaGo II), as well as my trusty old Celestron UpClose 10×50 binos. The choice of the C80ED was driven by two things: my space on the drive up was limited, so it was either the C80ED or the Apex 127 (which would have basically duplicated Steve’s rig), and I knew I’d want to do some wide field, low power observing, which is the one thing the Apex 127 can’t do.

For eyepieces, I spent most of the night using the 24mm ES68, which in the C80ED gives 25x and a sprawling 2.7-degree field. When I needed more power – which is much less often than I had anticipated – I bumped up to the 14mm and 8.8mm ES82s (43x, 1.9-degree field, and 68x, 1.2-degree field), and on a couple of tough double stars, the 6mm Expanse and 2x Shorty barlow. Unusually for me, I didn’t even mount a finder. With a 2.7-degree field, I can usually get the scope on target just by sighting down the tube. On those occasions when I needed more accuracy, I could lay my green laser pointer into a couple of shallow v-shaped notches on the tube ring and just move the scope until the laser was pointing where I wanted to go.

London Big Bear hike

Within moments of hopping out of the car, we could see loads of detail in the Milky Way with our naked eyes. The Double Cluster and the Andromeda Galaxy were both easy as well. Later on, we also spotted the excellent open clusters M35 and NGC 752 without optical aid. I logged the seeing as 4/5 and transparency as 5/5.

Our first few observations were “best in class” objects – the Pleiades, the Double Cluster and Stock 2. At low magnification under dark skies, the Double Cluster looks not so much like a pair of isolated objects, but rather a couple of thickenings or condensations in an incredibly rich Milky Way starfield. So it was that evening. Seeing that far above the horizon was rock steady and even at low mag, the C80 focused the stars down to tiny pinpoints of brilliant light. One of the clusters has a pair of red giants near its center – these were visibly brighter and more yellow than the rest of the cluster stars, even at 25x.

After that I turned west to catch M13 before it got too low. Going up to 68x revealed tantalizing hints of resolution – not bad for an 80mm scope.

M57, the Ring Nebula, was an arresting sight. At 25x, I could get both of the ‘corner’ stars that mark that end of the Lyra parallelogram, with M57 as a small but crisp circle of nebulosity floating in inky dark space. Although we also looked at the nebula with more magnification, I found that lowest-power view delightful. It reminded me of spotting the Ring at 12.5x in the TravelScope 70 three years ago – the view that first infected me with refractoritis.

We didn’t try to split Epsilon Lyrae until a bit later, when it was lower in the sky. The seeing there was only so-so and I had to push the scope to 200x, using the barlowed 6mm Expanse, to get a clean split, although both pairs were visible elongated at much lower magnification.

We stayed out long enough to catch the leading edge of the Big Dipper rising. One of the best views in that part of the sky is the galaxies M81 and M82 in the same field of view. They are close enough to be nicely framed in the same field even in the 8.8mm ES82. At that magnification (68x), M82 was starting to show tantalizing hints of structure.

London and Matt hiking above Big Bear Lake

The most memorable observations of the night were of the Auriga Messier clusters and the other Local Group spiral galaxies. Auriga clusters first – M38, M36, and M37 (from west to east, in the order that they rise) are seasonal favorites and fun to compare. We swept them up easily in binoculars and then scrutinized them in the scopes at progressively higher powers. I had a good laugh at M36 – at the orientation we saw it in this weekend, it looked like a short, fat stick figure, the bobble-head version of the Stock 2 stick-man. But M37 was my favorite, just an incredibly dense swarm of tiny pinpoint stars.

Fairly early in the evening we had a look at the Triangulum galaxy, M33. I was tracing out the constellation Triangulum with the GLP when we noticed a naked-eye glow that turned out to be the fine open cluster NGC 752. Neither of us could make out M33 with our naked eyes but it was dead easy in binoculars, and at 25x in the C80ED it showed considerable structure in averted vision, including what both of us independently took to be one of the spiral arms. Incredible.

We closed the session with another great view of a local galaxy. All through the three-hour session we’d been saying that we’d look at Andromeda, and then one thing or another would capture our attention and we’d get sucked into some other part of the sky. We finally got around to M31 and its companion galaxies a little after 1:00 AM. By that point they were basically at the zenith. Even with the tripod extended as high as it would go, we had to kneel to look in the eyepiece. But when we did, the view was astounding. M31 stretched all the way across the field, with only the very outer edges clipped by the eyepiece’s field stop. The little companion galaxies M32 and M110 were dead easy, of course, but what amazed me was that we could both see structure and detail with the main galaxy. I’d never seen those dust lanes in anything smaller than a 5-inch scope.

We knocked off after three solid hours of observing, exhausted but giddy. It was one of those transcendent nights that makes my heart sing, and also makes it really hard to go back to observing from suburbia. The most surprising thing for me was how much observing I got done with the 24mm ES68. “Small telescope at low power” does not scream satisfying deep sky observing, but under sufficiently dark, clear skies, I rarely needed anything else. I’m already looking forward to the next run.

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How to build a stand for a Dobsonian telescope

November 19, 2014

DIY dob stand 1

London got an Orion XT4.5 for his birthday last week. We’ve had it out a couple of times and it is an awesome scope. It strongly reminds me of my old XT6–the XT4.5 is a bit smaller, but probably not as much as you’d think from looking at photos of it. It’s solid, moves well, and the optics are great.

It is, however, too short. Even for London, and he’s just a bit over 4 feet tall. Clearly, we needed to get the scope up off the ground. The first night out, just to test potential setups, I put the scope up on an old plastic milk crate. This is the heaviest, sturdiest milk crate I’ve ever seen, and the scope still rocked back and forth on it. We needed a 3-legged solution.

Now, Orion makes a dedicated Dob stand that is really nice. It has grooves instead of divots to accommodate Dobs of many sizes. It also costs about $145, which I think is stark raving lunacy for 4 pieces of wood that any idiot could screw together.

DIY dob stand 2

The Dob stand I am about to show you will also accommodate any size of Dob, as long as you build it that way. It also costs next to nothing. For me it was precisely nothing since I used old crap I found in the garage: wood from a long-defunct futon (the same futon that gave some of its physical body to my old DIY Dob base), some metal shelf supports from a project that never got off the ground, screws from my “spare screw” box, and the modest tools I already owned, namely a saw and a handheld drill.

Step zero was to have London sit in one of the folding chairs that we use when we go camping or up Mount Baldy to stargaze, then set up the XT4.5 in front of him on the floor, pointing straight up, and measure the vertical distance between the eyepiece and his eye. As always when building anything to do with a Dob, it’s better to skew low–it’s always easier to bend down an extra inch to get to the the eyepiece at the horizon than it is to lift your butt an extra inch when the scope is pointed straight up. My rough target height for the stand was about 6 inches.

Conceptually this thing is dead simple: it’s just a ‘T’ of wood, reinforced on either side with the shelf supports. I figured out the dimensions by putting the XT4.5 down on a big sheet of paper and tracing the feet, and then laying the wood down on the paper sheet and tracing the cuts that I would need to make.

DIY dob stand - top close-up

Once I had the basic T-shape together, I set the XT4.5 on it and traced the feet again, directly onto the wood, then used a spade bit to drill out some depressions. The spade bit has a triangular tooth at the center that cuts a deeper hole, and that became the pilot hole for the screw that holds each leg on. So the legs are precisely below the feet of the Dob for maximum strength and stability.

DIY dob stand - foot close-up

In addition to the big screws that run down their long axes, the legs are reinforced with small angle brackets. These are probably overkill, but I wanted to build this thing once and then not worry about it for the next decade or two. In retrospect, angling the two “back” legs toward the center might have been smarter than making them parallel to the cross-bar. But like I said, this thing is probably over-built as it is.

DIY dob stand 3

The last step was to paint it with a couple of coats of black primer, which I also had lying around in the garage. The black paint definitely classes it up a bit. From a few feet away in the dark, you might even mistake it for something that had shipped with the scope.

How does it work? Wonderfully. I took care when I used the spade bit to cut the depressions so that the feet of the XT4.5 just fit inside their outer edges. Once the XT4.5 is settled in place, it will not slide or rock at all; it practically snaps in. You’d have to knock it over to get the ground board to move. You can grab the tube and swing it all over the sky and the ground board and stand stay put. And there’s no detectable vibration. The legs are each 5 1/4″ long and the T is 7/8″ thick, so the height is acceptably close to my “roughly six inches” goal. More importantly, London is able to observe comfortably while seated, whether he’s looking at Polaris low in the northern sky or the Andromeda galaxy dead overhead (and it was the other night, too, darn near straight up).

DIY dob stand 4

There is one final addition I want to make before I call it done: I want to sink a cap nut into the bottom of each leg. That way I can screw bolts of various lengths into the legs to make smaller feet. The stand as built does not rock on any surface on which I have tried it (driveway concrete, grass, and gravel so far), but the bottoms of the legs are long enough that it potentially could. Using bolts as feet would make the contact patches smaller and reduce the opportunity for rocking. Plus, that way the stand can grow with London: as he gets taller, we can swap out the foot-bolts for progressively taller pieces. I’d use cap nuts instead of T-nuts so the support bolts couldn’t punch through and damage the wood.* With a bigger Dob, I might put on casters. In fact, the swiftness and ease with which this thing came together–I did essentially everything but paint it in one afternoon–has got me thinking about building a rolling unit for the XT10. If that ever happens, you’ll read about it here.

* It just occurred to me as I was finishing this post that if it wouldn’t have upset London to start hacking on his brand-new scope, I could have sunk cap nuts into the ground board of the XT4.5 itself, and put long threaded bolts straight into them to make feet. If I ever get an XT4.5 of my own, I’ll probably do exactly that.**

** It further occurred to me after the post went up that the ground board already has threaded holes for the rubber feet, which have embedded bolts and screw in from the bottom. So in fact if I had thought it through I probably could have skipped the whole Dob stand entirely and just screwed 6-inch-long bolts into the ground board; if the included rubber feet are loafers, those long bolts would be stiletto heels. I haven’t actually tested that setup, mind you, but it seems like it ought to work.

If you don’t have a bunch of crap lying around in your garage, you can probably still build something like this for under $20, maybe less than half that if you can scrounge the wood. If you don’t have metal shelf supports and don’t want to spring for them, you could cut pieces of wood to reinforce each side of the ‘T’ diagonally. Painting is optional, the thing works just as well in its unpainted ugly state. If your woodworking skills are like mine–nearly nonexistent–you can also use the unpainted unit to make your carpenter friends cry. Have fun!

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The lunar ‘Cheshire Cat’ revisited, and problems of contrast

November 3, 2014

2014-11-02 London moonwatching

Just a quick post before I head off to work. London has the telescope bug and he has a birthday coming up, so we were looking at various scopes on Amazon and other places. He wasn’t clear on the distinction between the three main telescope designs, so we hauled out the DK Universe book and looked at the ray diagrams the three kinds (refracting, reflecting, and catadioptric). He was familiar with refractors, like his 60mm Meade, and reflectors, like his Astroscan, but was less familiar with catadioptric scopes, which is not super-surprising since I’ve used my Maks hardly at all in the last year and a half, other than last year’s All-Arizona Star Party. The sky was clear and the moon was high, so we popped outside and set up my 90mm SkyWatcher Mak for a quick look at the moon. Astonishingly, I had not had this scope out in more than two years, since July of 2012.

2014-11-02 waxing gibbous moon - snapseed

Here’s my best iPhone photo of the moon from last night. Up near the top of the terminator you can see two glowing dots like eyes peering over the limb of the moon. If you click through to the full-size version, you’ll see that the eyes have a wide mouth below them and that one nostril is showing. Yep, that’s the lunar “Cheshire Cat”, which I first identified back in November, 2010. It was nice to see it again.

While I was processing that photo I noticed something alarming: a circle of glare around the moon that was bright enough to make the eyepiece field stop visible. It’s more apparent in this over-brightened version:

2014-11-02 waxing gibbous moon - light scatter

I was shooting through the Celestron 8-24mm zoom, just like Saturday night. Since I had a comparable shot with the same eyepiece through the C80ED from that evening, I dug out the raw photo and tried brightening it up to see how much glare would appear.

2014-11-01 waxing gibbous moon - light scatter

The answer is “almost none”. I used the same tool in GIMP (‘Curves’), and I brightened the image way beyond what I did with last night’s shot through the Mak, and the space around the moon is still pretty black in the C80ED shot. Not grey, as in the Mak shot. And this was only with tweaking the brights up, and not moving the darks down, which would be cheating since it would mask the problem.

It’s tempting to read this as a refractor-vs-Mak thing, but it might not be so straightforward. In this case the refractor has very good optics and coatings, so it’s near the upper end of what refractors are capable of in terms of control of stray light. But the Mak does not have fully multi-coated optics–this SkyWatcher version only has ‘coated’ optics, which means possibly as little as one coat of MgF2 on only the outer surface of the corrector. I have heard from someone (Doug or Terry, maybe?) that this particular model of SkyWatcher 90mm Mak has poorer contrast than the comparable but fully multi-coated Celestron C90–irritatingly I cannot find that post or comment at the moment, but I’ll post it if it turns up. Also, the C80ED has a long-ish dew shield which helps control stray light entering the objective, whereas the Mak does not; you can buy or fashion such things for Maks, but I haven’t taken either of those steps. Finally, I’ve seen some threads on CN about glare from the baffle tube in Maks and SCTs, so that’s another possible culprit here.

An informative test would be to pit the C102 against the Apex 127 on the moon, with a homemade foam or cardboard dew shield on the Apex to eliminate that variable. If I get time this evening or next, I may just try that.

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Observing Report: All-Arizona Star Party 2014

October 30, 2014

 

AASP 2014 - loaded for bear

If it’s late October or early November, it must be time for the All-Arizona Star Party. London and I headed out for it this past Saturday, Oct. 25. As in 2012, we were joined by the indefatigable Terry Nakazono. Here Terry and London pose for the obligatory “look how much crap we crammed into the car!” photo.

We arrived at the site about an hour before sunset, plenty of time to set up camp and chat with the neighbors. As usual, we set up not far from Darrell Spencer and AJ Crayon, but irritatingly I failed to get a picture with Darrell, my first such lapse.

AASP 2014 - setting up in the shade

When we arrived the sun was still well above the horizon and temperatures were in the mid-90s. London and I set up our scopes on the east side of the car so we could sit in the shade. Here London is tinkering with his AstroMedia 40mm “plumber’s telescope”, which we just built last week. More about that scope in a future post. The scope behind London was another AASP newcomer.

C80ED newly arrived 1600

This is my new Celestron C80ED. This scope originally retailed for about $500. Celestron donated all of the remaining stock of the spotting scope version to Astronomers Without Borders, and AWB sells it for $350 with free shipping. Vicki got me one for our anniversary last week (and I got her some leather boots–in both cases, the choice of gift was, ahem, heavily influenced by the recipient). The package arrived on Thursday about half an hour before the partial solar eclipse was to start, so I just had time to take this photo before I ran out the door to London’s school.

I got this scope because it filled a hole in my lineup. My Maks have sharp optics but can’t do wide fields. The TravelScope 70 can do wide fields but still has limitations, even after its tune-up. And the C102 is a wonderful scope but not exactly small, and although its chromatic aberration is minimal it is still there. I figured a small ED scope could be a grab-n-go that could deliver wide fields like the TS70, take magnification on planets and double stars like the Maks, in a more convenient and false-color-free package than the C102. Plus I’d just always wanted to try an ED scope. I was going to get an AstroTech AT72ED but they are out of stock and have been for ages. The C80ED offered a small but significant aperture boost for less dough, so I bit–or rather, encouraged Vicki to do so.

I was going to bring both the C102 and the C80ED, but as the date got closer I decided that what I really wanted to do was put the C80ED through its paces under those dark Arizona skies, and another scope would just be a distraction. I had briefly set up the C80ED on Friday night to make sure the scope didn’t have anything seriously wrong. It didn’t–in fact, it star-tests as well as any scope I’ve ever owned.

AASP 2014 - refractor city

Turns out we were all rolling with small refractors. From left to right they are the C80ED, London’s 60mm Meade refractor, Terry’s Orion Short-Tube 80, and London’s 20×50 Orion spotting scope (reviewed here). Terry had been going to bring a 4.5-inch reflector but the Clear Sky Chart said that conditions were iffy. Also, like me he had been interested to see how deep he could push a small refractor under dark skies.

Incidentally, after bringing my XT10 to the AASP in 2010 and 2012, I brought the Apex 127 last year and now an 80mm refractor this year. At this rate, in a couple more years I’ll be down to bringing just a finderscope. (I jest, but I have had a longstanding interest in going to a dark site with only the SV50 or GalileoScope to see how many things I could see with a small scope under dark skies–so far, greed for photons has always won out, so this project remains unattempted).

AASP 2014 - moon in C80ED

Our first target of the evening was the waxing crescent moon. I got a few shots with the iPhone shooting through the C80ED. Here’s the best one. All I did was crop it and flip it left to right–other than the orientation change, the actual pixels have not been tinkered with at all. Note the absence of false color. I also put the scope on Vega early in the evening and could not detect any false color–very impressive.

On the drive out, Terry asked me if I had any plans or goals for the evening. I did have a few:

  • above all, spend some time observing with London;
  • look at some familiar objects to get a feel for the scope;
  • track down some southern objects, since I’d be at a dark site with a clear and dark southern horizon;
  • to the extent that I could, test the scope on challenging targets like globular clusters and close double stars.

And that is more or less what I actually did.

A word about the sky conditions before I get into actual observations: they were not fantastic. Seeing was lousy the whole night, with the stars twinkling visibly all over the sky. Transparency was good in the early evening but around 9 or 10 a very light haze set in across the whole sky. It wasn’t ghastly, but it noticeably knocked down the contrast–where the Milky Way had blazed overhead at 8:00, by 10:00 it was just sort of there, visible but not nearly as prominent. In my notebook, I rated the seeing at 2 out of 5 and the transparency at 3 out of 5.

I only used four eyepieces for most of the night:

  • 24mm ES68, which in the C80ED gives a magnification of 25x and a true field of 2.7 degrees
  • 14mm ES82 (43x, 1.9*)
  • 8.8mm ES82 (68x, 1.2*)
  • 6mm Expanse (100x, 0.67*)

I did use a 32mm Plossl to drop the power down to 18.75x to see if Polaris could still be split (it couldn’t, but read on), and I used a Barlow once. Other than that, it was just these four, and out of these four, I used the 24mm and 8.8mm EPs significantly more than the other two. I had planned to use the 8-24mm Celestron zoom, but in testing the scope Friday night, I could tell that the Explore Scientific eyepieces were noticeably sharper. Good heavens, I think I’m turning into a refractor weenie and an eyepiece snob.

After the moon we visited Mars, but it was tiny and featureless and fairly burning in the bad seeing. Then I swung next door to Sagittarius and got my first surprise of the evening: the big glob, M22, was partially resolved even at 25x with the ES68! I love globs–they are one of my chief joys in observing with the XT10, and I expected them to be dim, featureless cottonballs in the C80ED. That I was getting partial resolution on one in a small scope at low power was pretty arresting. I had a quick look at M28, M8, and M24, and then helped London get his 60mm on target on M22, M28, and M8. London was interested in seeing a double star so we wheeled the scopes around and had a look at Mizar and Alcor. Then we looked at M13, M57, the Pleiades, the Double Cluster, and Stock 2 in his 60mm.

AASP 2014 - our camp

Highlights of the Evening: M13, M57, M27

After all that, London went to lie in the lounge chair and watch for shooting stars–he got 17 before he went to sleep around 10:30. I went on to M13, the Great Globular Cluster in Hercules, and had my socks knocked off. Like M22, it was partially resolved even at 25x, and much better at 68x and 100x. It wasn’t fully resolved, of course, and the XT10 will blow away the C80 on this or any other glob, but it was at least a ball of many, many stars and not just a fuzzy blob. Here’s one of the nice things about widefield eyepieces and short focal length scopes: you get huge fields even at reasonable magnifications. At 68x in the 8.8mm ES82, I could park M13 comfortably inside the field stop and watch it drift across the field of view for more than four minutes. Even at 100x in the 6mm Expanse, I could watch the cluster drift across the center of the field for a bit over two minutes. I commented to Terry that if I hadn’t had other things I wanted to see, I could have kept watching M13 all evening and been very happy.

Lyra was still pretty high overhead so I went there next. Epsilon Lyrae was shimmering in the bad seeing. It was elongated at 68x and almost split at 100x, but I had to Barlow it up to 200x to get a clean split. You may recall that under better conditions, the TravelScope 70 split the Double-Double at 133x, and I know that it is often split at well under 100x by high quality small refractors. So the high magnification required for the split here reflects more on the quality of the seeing than on the quality of the telescope. I’m looking forward to seeing how the C80ED performs on Epsilon Lyrae on a better night.

M13 was probably my favorite view of the night, but a close runner-up was M57, the Ring Nebula. It was clearly ring-like at 68x, but I liked it even better at 25x–the expansive 2.7-degree field of the ES68 showed the nebula nicely framed between Beta and Gamma Lyrae (the stars that mark the south end of the constellation stick-figure) and their attendant stars. It reminded me of the view of the Ring at 12.5x in the TravelScope 70 back in 2012, which is what got me into refractors in the first place.

After that I spent a few pleasant minutes rocking through the Lyra-Cygnus-Sagitta axis, observing M56, Albireo, Brocchi’s Coathanger (Cr 399), M71, and M27. Interestingly, the view of the M27 was very similar to the one I had through the C102 at the Salton Sea last year: I could not only see the “apple core” extensions, but also some of the “football” nebulosity between those extensions. That is a lot of nebulosity to pick up in an 80mm scope. I wonder what I could see on a night with better transparency.

By now it was about 8:50 and I knocked off the serious observing for a while. First I went to hang out with London, and while he watched for shooting stars, I used the 15×70 bins to sweep up many of the same summer showpieces I’d just seen in the telescope: M57, M56, Albireo, Cr 399, M71, M27, M13, the Double Cluster, some of the nice NGC open clusters in Cassiopeia. Then some folks from the other end of camp stopped by and we chatted for a while. Darrell came over and had a look at M13, and London and I went down to the center of camp to get some hot chocolate. When we got back, London sacked out. I had a quick look at M11 before it set, and tracked down the asterism DeLano 1 just to make sure it was still there. Then, at Terry’s suggestion, I tried M15, the big glob off the nose of Pegasus. Here are my unedited notes:

M15 – tough nut to crack. Starting to look grainy at 100x. Also pretty grainy at 68x in 8.8mm ES82. Even though it only gives about 2/3 the magnification of the 6mm Expanse, I think the 8.8mm ES82 shows almost as much. It’s just a superior piece of glass. Another ES82 or 68 in the 3-5mm range should be priority.

Now, this idea that the 6mm Expanse is maybe not 100% awesome–hold onto that thought, we’ll revisit it at the end of the evening.

IMG_2140

Go South, Young Man

Ever since my incredible Salton Sea run with David DeLano last fall, I have been painfully aware of how much I’ve neglected the southern sky. So from 10:45 to 12:30, that’s where I went. My first southern target was NGC 7293, the Helix Nebula. It was dead easy to see once I got there, but it took me an unusual amount of faffing about to get on target. I was using the 6×30 straight-through correct-image finder that came with the C80ED. I’m normally a RACI man so using a straight-through finder took some getting used to. But I kinda like it, now that I have the hang of it.

After that it was onto some galaxies and planetaries: NGCs 55, 300, 288, 253, 247, 246, 720, and 779. NGC 288 and NGC 253 were nicely framed in the same field. NGC 288 is a globular cluster circling our own Milky Way galaxy, about 29,000 light years away, whereas NGC 253, the Silver Coin galaxy, is 11.4 million light years away, almost 400 times farther, and rivals our own Milky Way in size. So that pair has a bit of the M97/M108 ‘odd couple’ thing going on.

The not-quite-edge-on galaxies NGC 720 and NGC 779 were my only new objects for the evening. Both of them are on the Herschel 400 list, and bring my H400 tally to 175. I am starting to wonder if I will ever finish the Herschels–the only new ones I’ve notched in the past couple of years have been bagged at the All-Arizona Star Party. I gotta get out in the spring more. I’ve just about exhausted the fall Herschels, but there are hundreds of spring galaxies to observe in Ursa Major and the Virgo-Coma Cluster.

C80ED AASP 2014 2000

Orion and Points North

After almost two hours of faint fuzzies, I was ready for a change of pace. I turned east, toward Orion. The view was pretty great–the Trapezium was split into four components at only 25x, and the nebulosity seemed to go on forever. And yet, the subtle gradations in the nebulosity did not seem as pronounced as I had observed on other nights. Terry noticed the same thing observing Orion through his ST80. He thinks that the poor transparency was leaching some of the contrast out of the view, and I am inclined to agree.

Without a doubt, the strangest observation of the night was of NGC 1980, the field of nebulosity around Iota Orionis. When I looked right at the nebula, it was steady, but when I looked back at M42/M43, NGC 1980 would flicker in my averted vision like a bad fluorescent bulb. At first I thought maybe it was just my eyes, but I called Terry over and he reported seeing the same effect.

Now, I don’t think that the nebula was actually flickering. I suspect that through some quirk of eye/visual system physiology, it only seemed to flicker in averted vision.

Just to rule out the obvious distractors: we were parked on the very east end of the airstrip so there was probably no-one between us and Phoenix. Neither of us were using flashlights or any electrical gear at all while we were observing in Orion. Our nearest neighbors were about 50 yards to the NW and SW, and they’d all turned in for the night. So I’m about as certain as I can be that it wasn’t some terrestrial source that just happened to be shining into the eyepiece or objective lens. Also, we only noticed the flickering on NGC 1980, and not on the extended “wings” of nebulosity from M42, which were of similar brightness at their extremities.

Has anyone else seen anything like this, either for NGC 1980 or other DSOs? If so, I’d love to hear about it–the comment thread is open.

After Orion’s Sword I bounced around a few northern Messiers–M78, M1, M35 with NGC 2158 just starting to resolve behind it, M81 and M82 in the same field, and M97 and M108 in their own field. Midway through that tour I stopped to split Polaris. It was continuously split at 24x in the 24mm ES82, not split at 18.75x in the 32mm Plossl. This illustrates just how seeing-dependent double star splitting is–Friday night from my driveway, the seeing was even worse, and that evening Polaris was not continuously split at 25x, but it was a 43x in the 14mm ES82, and even at 28.5x in the 21mm Stratus. As indicated above, the seeing out in Arizona Saturday night was not awesome. One of my quests with the C80ED is to see how low I can go, magnification-wise, and still get clean splits on some of the classic double stars. Watch this space.

M97 and M108 were my last DSOs of the evening. After that I turned to Jupiter, and even at 68x I could see at least 4 belts. The Galilean moons were spaced about evenly, two on each side of the planet. Terry and I compared views of the planet through the C80ED and his ST80. We could get similar magnifications with our favorite short eyepieces: the 8.8mm ES82 gave 68x in the C80ED (FL = 600mm), and the 6mm Expanse gave 67x in the ST80 (FL = 400mm). So how did the scopes compare? Well, obviously the ST80 was throwing up a lot of false color, but I could detect the same four belts that I could in the C80ED, albeit not quite as crisply. More informative was the comparison of eyepieces. Terry had a 6mm Expanse clone from AgenaAstro.com. While were swapping all of these eyepieces between the two scopes–the 8.8 ES82, the 6mm Expanse, and the 6mm Expanse clone–I noticed something I had never spotted before: the 6mm Expanse threw up a huge circle of glare around Jupiter. Perfectly circular, like a lens flare, centered on Jupiter, and spanning out to the outermost moon on each side. The glare circle was there in the 6mm Expanse in both scopes. It was not there in either scope in the ES82, nor in the AgenaAstro Expanse clone. These are the Agena Enhanced Wide Angle (EWA) 6mm, which goes for $45 (you can find it here), and the 6mm Orion Expanse, list price $68, street about $59. So if you’re in the market for a 66-degree EP, you can save about 25% and get noticeably better performance from the Agena version. I’m tempted to get one myself, and hock the Orion EP. Until now, the 6mm Expanse has been one of my most-used EPs, but now that I can see its faults…like I said, eyepiece snobbery is taking hold.

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Settling Up

After one last look at Jupiter in the ES82 at 3:00 AM, I shut down and went to bed. The next morning, London and I went on our customary “bone hike”, and we did find several bones, including a couple of cow limb bones, and the jackrabbit lower jaw shown in the photo. More exciting were the Western diamondback rattlesnake and the horned lizard that we found.

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My final tally for the evening was 45 telescopic objects:

  • 2 planets (Mars and Jupiter)
  • 22 Messiers
  • 13 other NGCs
  • 2 asterisms (Brocchi’s Coathanger, DeLano 1)
  • 1 other catalogued DSO (Stock 2)
  • 5 double/multiple stars (Mizar/Alcor, Albireo, Epsilon Lyrae, Trapezium, Polaris)

…plus a couple of meteors.

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Irritatingly, I realized later that I had completely missed out on some real gems. I never once pointed the scope at the Andromeda galaxy or its satellites–detail in M31 would have been a good test of the C80’s optics. And I skipped the nice open clusters in Auriga–M36, M37, and M38–which maybe more than any other set of clusters give that “diamonds on black velvet” feeling in a sharp telescope. We set up early enough that I could have rocked through all of the Sagittarius Messiers instead of the handful I actually saw, but I deliberately traded that time away to help London find some things, so I don’t feel bad about that particular omission. The others are a bit galling.

Even with those omissions, I still met all of the goals that I had set for myself: I got in some good observing time with London, I had fun touring the southern skies, even if most of the things I saw there were revisits, and I both got a feel for how the scope performed on average targets, and got to push it on some challenging ones. The biggest revelation to me was that an 80mm scope would start to crack open some of the bigger globs. M13 and M22 didn’t just look good, they looked stunning. I wish I was observing them right now.

In sum, a great night of stargazing, and a pretty thorough field test for the C80ED. I think I am going to have a LOT of fun with this scope.

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Observing Report: Night of the Refractors redux

November 20, 2013
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From left to right: my TravelScope 70, my C102, David’s C102. When I took this picture, we hadn’t put the finders on the big scopes yet, or gotten my stand-alone GalileoScope set up yet.

This one is a little late: David DeLano and I spent the night of Sunday, November 3, observing at the Salton Sea. This is the belated observing report.

We met up at the visitor center at the headquarters campground. We rendezvoused there a little after 3:00 in the afternoon because we had some things to do before sunset, which because of the time change was coming at 4:50. The visitor center gift shop has a little astronomy section and both of us picked up a copy of the Sky Atlas for Small Telescopes and Binoculars, by Billie and David Chandler–more on that atlas another time. David also picked up a nice plasticized version of the Chandler planisphere.

Chandler Sky Atlas

After that we drove down to my favorite spot at the Sea, which is the south end of the Mecca Beach campground. A couple at another site were loading up as we were pulling in, and the left a few minutes later. After that, we were the only humans at the campsite all night long, except for someone in the late evening who pulled in, turned around, and left, all without stopping.

Our first activity was dinner at a picnic table in the shade. We split the gear and groceries like so: David supplied firewood and snacks, and I brought dinner (Subway sandwiches) and cooked breakfast (pancakes).

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Even as we were eating, the second activity commenced: the exchange of hostages. As far as I can tell, David is a hot rod mechanic who happens to work on small refractors instead of cars; if that strikes you as hyperbole, just read on. Anyway, he’s way more adept at getting refractors to sing than I am, so I had brought him an unfinished Carton 60mm f/15 refractor and a couple of small objectives that I had rescued from otherwise unsalvageable garage sale scopes. To transfer into my care, David had brought a nice Celestron 2-inch star diagonal for my C102, and–most importantly–a GalileoScope that he had built and modded for me.

Galileo is Rocking Out in His Grave

The GalileoScope was created for the International Year of Astronomy in 2009, when it originally sold for $15. That was mostly down to economy of scale; now that sales have cooled, the price is up to about $50. It’s still a lot of telescope for that price. David’s GalileoScope mods have been featured here before.

The stock GalileoScope is a straight-through instrument with an f/10 objective and a push-pull focuser, which you aim by looking along some gunsight-style ridges on top of the OTA. My GS has had its tube chopped to accommodate a Stellarvue 90-degree diagonal with a helical focuser (the #D1026AF unit here, if you want one for yourself), and has a Daisy red-dot finder perched on the forward gunsight.

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Above, my nicely tricked-out GalileoScope. Bottom, David’s insanely modded version–possibly the most attention anyone has ever lavished on a cheap build-it-yourself 50mm refractor.

Lest you get too jealous of my pimped-out GalileoScope, let me describe David’s own GS. He got the aftermarket f/11 objective kit, which lengthens the light path enough to allow the use of a diagonal without chopping the tube. At the back end of the scope, there’s a 2″ Crayford focuser (yes, you read that right) with a 1.25″ adapter. His diagonal also has a helical focuser for fine-tuning; in fact, in use I forgot about the Crayford and used the helical focuser exclusively. At the front end, there’s some kind of fancy RDF, sold by Cabella’s for use by hunters, with the largest eye-lens I’ve ever seen apart from the “boxy” astro-only unit-power finders, the Telrad and the Rigel Quikfinder. A set of nice rings with Delrin-tipped screws completes the instrument, and allows David to mount it coaxially with his larger scopes as possibly the most awesome luxo-finder-slash-second-instrument that I’ve ever encountered (on a small scope; the 9.5-inch refractor mounted on the 12-inch Zeiss in the Griffith Observatory probably takes the cake for larger instruments).

David’s GS really must be seen to be believed. Once on the Dinosaur Mailing List, Mickey Mortimer wrote, “Looks like it’s time to over-technicalize this previously tame post.” I can’t think of David’s GS without those words going through my mind. I wouldn’t be surprised if it is the most extensive hack anyone has done on a GS. It is definitely the most badass.

I should mention that getting both of the GalileoScopes to work as well as they do involved a lot more than just throwing some nice parts on. It required a lot of work and thought and experimentation. Happily, David documented the process and will have a guest post about his adventures in GS-hacking in the not-too-distant future. So stay tuned for that.

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David’s GS mounted on his C102 as the luxury finder to end all luxury finders.

After dinner and the exchange of hostages, it was time to set up scopes. I was rolling with the C102/SV50 combo again. I also set up the TravelScope 70 just to have something different to plink around with. David set up his second tripod for my GS, and put his mod-tastic GS on his own C102, using a third tube ring to support the GS stalk and rings. This makes for an imposing setup. I studied it as intently as an American astronaut getting his first look under the hood of a Soyuz capsule. We used some antennas on a distant mountaintop to get everything aligned, and then almost immediately we were off and running.

Skyward!

Our first target, at 5:30, was Venus. There wasn’t much to see–basically a very bright half-circle–but checking in just feels like the right thing to do.

Next we turned to the Double Cluster and Stock 2 and spent a few enjoyable minutes tracing out the loops and chains of stars in our various instruments. Like last time, I could see the red stars in NGC 884, and if anything they were easier this time since I knew what to look for.

After that we turned south and did a big tour of the Sagittarius/Scutum area, eventually going north into Aquila and then west through Serpens to Ophiuchus. But I’m getting ahead of myself.

We started with the teapot asterism in Sagittarius, and let that guide us to M8, the Lagoon Nebula. Then we hopped up just a bit to M20 (the Trifid Nebula) and the open cluster M21. After that we took a break to hit M13 in Hercules before it sank down into the light dome over Palm Springs. We returned to Sagittarius with globs on the brain and took in M22, which I thought was a serious contender in the field of majestic globs. Then it was up to the M24 star cloud, where we got lost for a few minutes at the sight of literally thousands of stars in our eyes. Somewhere in Seeing in the Dark–and irritatingly I cannot find the passage right now–Timothy Ferris describes a swath of the sky, possibly M24, as a “wonderland of far-flung suns”. Whether he intended it for M24 or not, it’s an apt description.

At the risk of letting my current bout of refractoritis get the best of me, I must say, the view of M24 through the C102 was just breathtaking. Now, I have visited M24 before, many times. It is one of my favorite places in the sky. But I had not taken a good look at it through a decent-sized refractor under dark skies. The contrast was superb: against a jet-black background, the stars were so finely graded by brightness that I noticed rivers and shoals among them that I had never been aware of before, including a current of brighter stars running north-south and paralleling the Milky Way. Truly, this is the backbone of night.

But even in a palace, one can want for variety (or so I’ve heard), so we ventured onward. Past the open cluster M18 we came to the Swan Nebula, M17, very bright and clear and looking just like its namesake. Then farther up we found M16, the Eagle Nebula, its tendrils of glowing gas wrapped around a dense cluster of newborn stars. Then back to M24 to pick up the open clusters M25 and M23, which attend the majestic star cloud like obsequious courtiers. M25 is one of my favorites; it sits at the center of a curving arc of stars that David describes as a spiral, but that to me has always looked like a fishhook, with M25 as the bait.

After working through all of those objects with the scopes, we stopped for a binocular tour. I had along my Nikon Action 10x50s and David was rolling with his Nikon action 10x40s. I found that if I held David’s green laser pointer between two fingers of my right hand and the binoculars, I could aim the laser beam at the center of my field of view. We shared many sights over the course of the evening using this trick. For starters, we revisited all of the Sagittarius clusters and nebulae mentioned above, and picked up the little glob M28 as well.

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The asterism “DeLano 1” next to Mu Aquilae. It is much more obvious than this Stellarium view shows, and looks more like a bright open cluster.

Then we turned north to Scutum and Aquila. Our first stop was M11, the Wild Duck cluster. Then I took a break for bathroom and snacks, and David went crazy finding new things. When I got back to the scope, I had some catching up to do: the open clusters IC 4756 in Serpens, and NGC 6633 and IC  4665 in Ophiuchus. David had also discovered something pretty that was not listed on any of our charts: a small group of bright stars just north of Mu Aquilae. So far I have not found this listed anywhere as a named object; for the heck of it we called it DeLano 1.

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A closer view of DeLano 1.

Zoom Zoom Zoom

I see that I have not mentioned what I was using for eyepieces. Thanks to the 2″ diagonal I could use my 32mm Astro-Tech Titan, which gives a wider true field than any other eyepiece I own. In the C102 it gives a magnification of 31x and a 2.2-degree true field of view, which was great for framing almost everything we looked at (the Pleiades fit with a little room to spare, even). My only other 2″ or dual-barrel EPs are the 21mm and 13mm Orion Stratus EPs, which I used infrequently Sunday night. When I wanted more power, I put in the 1.25″ adapter and my new toy, the Celestron 8-24mm zoom eyepiece.

My only previous experience with a zoom EP was a Scopetronix 7-21mm, which was pretty stinky. Zoom EPs always have wider apparent fields of view at high magnification and narrower AFOV at low magnification. That is pretty much the opposite of ideal, but physics is physics, and the comparatively narrow apparent field is tolerable as long as it doesn’t get too narrow–below about 40 degrees you feel like you’re looking through a soda straw. Unfortunately, with the Scopetronix zoom, the AFOV started at 40 degrees (at high mag) and ended up somewhere below 30, at which point the image is so small you might as well be looking through the other end of the telescope.

Happily the Celestron 8-24mm zoom has a more generous AFOV. The stated range is 40-60 degrees, and that seems about right to me. What’s not so great? It’s not parfocal across its magnification range (I don’t know how many zoom eyepieces are), so you have to refocus as you change magnification. Also, it’s a little soft at high power. Not egregiously so, but my 8.8mm ES82 is not going to be losing any sleep. On the plus side, it’s decent, convenient, and at a current street price under $55, dirt cheap.

Incidentally, this is the danger of getting a couple of high-end eyepieces: they are so sharp and so clear that when you go back to merely average EPs, the differences are immediately noticeable. It makes you spoiled.

Lyra, Cygnus, Vulpecula, and Sagitta

After I got caught up in Ophiuchus, we turned north, first to Polaris and the “Engagement Ring” asterism, and then to the Lyra/Cygnus/Sagitta area.

Naturally our first stop was Epsilon Lyrae,  the “double double” star, which was cleanly split at 125x with 8-24mm zoom. So if you’re curious about that eyepiece, there’s a point in its favor.

After that we followed my usual J-shaped path through this  region: from the Ring Nebula, M57, on past the fair-to-middlin’ glob M56 to the brilliant, contrastingly-colored double star Albireo. Like a lot of double star observers, I like doubles when they’re not too widely split, and at 31x the 32mm Titan and C102 gave perhaps the best view of Albireo I’ve ever had in a scope. After Albireo, go straight south to find Collinder 399, better known as Brocchi’s Coathanger. Southwest of the Coathanger one comes to the pair of closely-spaced, equally-bright stars that mark the feather end of the constellation Sagitta, the arrow. Halfway along the arrow a zig-zag pattern of stars leads to the faint glob M71. Then proceed along the arrow to the third bright star up from the feathers and hang a right to find M27, the Dumbbell Nebula.

The Dumbbell does a neat trick as either one’s scope or one’s sky conditions improve. From a small scope, or a big one under city lights, it looks like a bow tie. As things get better, the ends of the bow tie sprout extensions to either side, so the nebula starts to look more like an apple core. Finally the area to either side of the apple core starts to fill with nebulosity, so the nebula ends up looking like a football with a bright band–the former bow tie/apple core wrapped around its “waist”.

10-04-2008_DumbellThe football form of the nebula is obvious in most astrophotos of M27. Here’s a nice example by Rogelio Bernal Andreo (DeepSkyColors.com) that shows the different aspects in different colors: white bow tie center, red apple core extensions, blue football wings. I have seen the football before in the XT10, but I had never seen it in a small scope before Sunday night. And, to be clear, the C102 did not show the entire football. But it did definitely show the wisps of nebulosity extending out on either side of the apple core. It’s probably  best to say that M27 was halfway between  the apple core and football forms. It was missing the crisp cut-off at the edge of the football, which the XT10 will show under sufficiently dark skies. But it was still way more than I expected. I am still learning what a 4-inch scope with high contrast can do under dark skies; the answer is, “an awful lot”.

The striking appearance of M27 can in part be chalked up to excellent transparency in the early evening. Another example is that both of us could clearly make out the North American Nebula, NGC 7000, in the binoculars. My best-ever views of the nebula have been with 15×70 bins out at Owl Canyon. I have caught glimpses of it in the 50mm glasses before, but never as good as it was Sunday night. David was getting it clearly in his 40mm bins, which is pretty amazing.

We did another binocular tour in this area, hitting all of the objects listed above as well as M29, M39, the heart-shaped asterism around the bright star Sadr in the heart of Cygnus, and the wide blue/orange binocular double Omicron Cygni. This was about 8:30 PM, four hours into our 9-hour run.

This is pretty much how we proceeded for the rest of the night: pick an area, figure out some of the best and brightest objects therein, and hop our way through them. David was working off the Evening Sky Map and suggesting objects from its lists, and I was working from the PSA and rediscovering some goodies I hadn’t seen in a while. Rather than give an exhaustive list of everything else we saw, I’ll just list some highlights:

NGC 253 and NGC 288 – NGC 253 is the Silver Coin Galaxy. It’s up there with Andromeda (M31), the Whirlpool (M51), the Sombrero (M104), and Bode’s Nebulae (M81 & M82) as one of the best galaxies for northern hemisphere observers. My first view of it was in binoculars from Big Bear Lake, and under those dark mountain skies it looked as good in the 15×70 bins as a lot of galaxies look through a telescope. Mottled details is visible in even small scopes under sufficiently dark skies. While you’re in the area, might as well drop down about one eyepiece field and pick up the globular cluster NGC 288.

NGC 7789 – Here’s one I’d seen before but forgotten about. This is a nice open cluster off the tip of Cassiopeia, sandwiched between two small groups of bright stars. There are a lot of open clusters in Cassiopeia–we did a third binocular tour that encompassed NGC 457, NGC 436, M103, NGC 663, NGC 659, NGC 654, and Cr 463–but NGC 7789 might just be the best, not only for its inherent charm but for the rich surroundings in which it is set.

M37, M36, M38 – This is the famous trio of open clusters in Auriga, which are among the most popular and  most visited objects in the winter sky. The one that impressed us the most Sunday night was M37, the lowest (east-most) one. It is a dense swarm of tiny stars, which David described as “crystals”, and which to me looked like the proverbial scattering of diamonds on black velvet.

M46, M47, M93 – These open clusters in Puppis are also popular winter objects, especially the close pair of M46 and M47. I suspected the planetary nebula NGC 2438 in M46, which I first spotted at the All-Arizona Star Party back in 2010. Since then, I always look for it, and when I do spot it, I wonder how I was able to go  for so long without seeing it.

M76 – This is the Little Dumbbell Nebula in Perseus, and one of just a handful of planetary nebulae in the Messier catalogue (the others are M27, M57, and M97). As its name implies,  the Little Dumbbell is the smallest and probably least impressive of the Messier planetaries, but I’ve always had a fondness for it. Although small, it has a high surface brightness so it’s not hard to spot if you know where to look, and it is not without its charms.

Planetary nebulae illustrate why the Messier catalogue is a two-edged sword. On one hand, the Messier catalogue does include some best-of-class objects in almost every category of DSO; on the other hand, there are numerous objects in other catalogues that outshine (sometimes literally) the less impressive Messiers. For galaxies, you have things like the Silver Coin and NGC 4565 in Coma Berenices; for open clusters, look no farther than the Double Cluster in Perseus and NGC 663 and NGC 7789 in Cassiopeia; for diffuse nebulae, see the Flame Nebula (NGC 2024), the Rosette (NGC 2237), and the Christmas Tree or Cone Nebula (NGC 2264).

But planetary nebulae get especially short shrift; a quick-and-dirty list of impressive non-Messier planetaries in northern skies includes the Cat’s Eye (NGC 6543), the Eskimo (NGC 2392), the Saturn (NGC 7009), the Ghost of Jupiter (NGC 3242), and the Blinking Planetary (NGC  6826). This is not because Messier had anything against planetaries but because his catalogue was discovered rather than assembled post-hoc, and discovery is always a haphazard process. Still, we are not discovering these things for the first time, and with their often high surface brightness and charming array of forms, planetary nebulae are great targets for beginning and city-bound observers.

By 2:00 AM we were winding down, and so were the skies. A cloud mass that had been hovering over Palm Springs started to send forth offspring, and the haze near the horizon was getting worse. A bright star in Leo that I just couldn’t place turned out to be Mars. We had one last look at the Double Cluster and called it a night.

It was one of the most fruitful observing runs I’ve ever had. By my count, we looked at:

  • 49 Messiers
  • 20 NGC, IC, Collinder, etc., objects
  • 4 double stars (counting Epsilon Lyrae only once)
  • 4 asterisms (DeLano 1, the Engagement Ring around Polaris, the Heart around Sadr, and Kemble’s Cascade)
  • 3 planets (Venus, Jupiter, Mars)

So about 80 things in the sky, not counting the numerous shooting stars, which we noted every few minutes all night long. That is by far the most things I’ve seen in one evening when I wasn’t doing a Messier Marathon. But we weren’t rushing or trying to get through a ton of objects, we were just basically out for a spin, and if you cruise around the sky for 9 hours, you are going to end up seeing a lot.

Lessons

I came away from the evening with a couple of firm directions for future observing.

First, I don’t think I logged anything that I hadn’t seen before (DeLano 1 excepted!), but I saw a lot of stuff that I had forgotten about, like NGC 7789. Most of these were things that I had visited in the course of doing one or another Astronomical League observing program. That’s great because those programs have helped me to learn the sky, and they’ve introduced me to a lot of wonderful objects that I hadn’t seen before. But now that I know the sky, I need to go back and re-observe those things and spend a little more time with them. This is especially true of the many beautiful clusters on the Deep Sky Binocular observing list–I am ashamed to say that there are many of those that I still have not visited with a telescope. So even my terra cognita holds some wonderful things waiting to be rediscovered.

Second, I need to go south (in the sky)! Here’s some relevant math: the Salton Sea campgrounds are at about 33 degrees north latitude. That means that Polaris is 33 degrees above the northern horizon, the celestial equator is 57 degrees above the southern horizon, and with no intervening landforms or atmosphere I should be able to see down to -57 degrees declination when I look south. Now, in practice the near-horizon haze makes the last few degrees pretty worthless. But I have seen the globular cluster Omega Centauri with my naked eyes from the Salton Sea. At -47 degrees declination, it never gets more than 10 degrees from the horizon. If it’s naked-eye visible that low under good conditions, then binoculars and telescopes will reveal much more at the same declination, and maybe even a little lower.

In practice, I have explored almost none of that southern expanse. I am used to thinking of the Silver Coin galaxy as a far southern object, but at -25 degrees it culminates a full 32 degrees above the horizon–more than a third of the way to the zenith! Except for sighting Omega Centauri a couple of times, I have not deliberately gone south of about -30 degrees declination (and I’ve only gotten there in the area around the “tail end” of Canis Major), which leaves a LOT of unexplored sky out there. I was fortunate to get to see most of the best of the southern hemisphere sky when I was in Uruguay in 2010 and it was amazing. Much of what I saw there is visible from here, I just haven’t looked. I need to fix that.

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Big fish with light tackle

October 20, 2013

From the first time I read it, I have had a strange fascination with Jay Reynolds Freeman’s “Refractor Red meets the Herschel 400” (available here), wherein he describes observing the legendary deep-sky list with a 55mm refractor. Freeman wrote, “Ask people who land big fish with light tackle, why I do what I do.”

Lately I’ve been working through a slew of the open clusters in the Herschel 400 myself. And I have found that some clusters are dead easy to recognize as distinct bright patches in my 9×50 finder, but at the eyepiece they just sort of dissipate into the background starfield. That plus some fairly transformative rich-field experiences with small refractors (like this one) are working some kind of alchemy on me.

In a feat of Freeman-like proportions, my friend and frequent 10MA contributor Terry Nakazono has logged and sketched over 500 DSOs in the past 3 or so years, including 368 galaxies, almost all with scopes under 5″ aperture, mostly from at least somewhat light-polluted skies. He is just religious about dark adaptation, averted vision, and patience.

Possibly as a result of all of the above, lately I have had this mad desire to go out to the desert with a 70mm or even a 50mm refractor and spend the whole night observing with only that instrument. It feels like my reverse aperture fever and my deep-sky interests are slowly colliding. That plus a sort of perverse desire to knowingly commit to a “suboptimal” (aperture-wise) observing program just because it sounds fun.

I shared this plan on CN and fellow user blb wrote:

No mater what size telescope you use, it seems that you are looking at objects that are on the limits of what can be seen with that size scope. Once I realized this and read, some years ago now, what Jay Reynolds Freeman had to say about his observations, I came to realize there were way more objects to be seen in a small telescope than I would probably see in my lifetime.

I think this is exactly right; I find that with whatever instrument I have to hand, I tend to throw myself up against its limits.

AstroMedia plumber's telescope: a 40mm achromat made with plastic plumbing fittings

AstroMedia plumber’s telescope: a 40mm achromat made with plastic plumbing fittings

In particular, I know that all of the Messier objects have been logged with a 50mm telescope. What about a 40mm scope? I see that AstroMedia has a 40mm f/11 achromat kit (also available from AstroMediaShop.co.uk). That is strangely fascinating to me. (It would be simpler to use a larger scope and simply stop it down to 40mm, but somehow it seems more “pure” to use a scope with a native aperture of 40mm.) However, I think I would first do a Messier tour with a Galileoscope; just because other people have found all the Messiers with a 50mm scope doesn’t mean that I will, and it makes sense to start with that easier goal before plunging right into uncharted territory. It would be mighty tempting to put the 40mm scope and the Galileoscope on the same mount, though…

So…I’ll keep you posted.

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Revenge of the Celestron Travel Scope 70

October 15, 2013

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Update: This post seems to get a lot of traffic, especially around the holidays. If you’re looking for good gifts for amateur astronomers, including telescopes and binoculars that won’t break the bank, you may also be interested in myastronomical wish list for beginning stargazers.

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Last year I picked up a Celestron Travel Scope 70, mostly because it was cheap (~$65) and I was curious. Except for a couple of quick peeks with the scope, the only serious workouts it got were the transit of Venus and an all-nighter on Mount Baldy.

My feelings at the time–explained here–were that the scope was great a low-power scanning but useless at anything over 50x. Terry Nakazono suspected it was miscollimated, but I’d never collimated a refractor and I had plenty of other stuff to be getting on with, so I let the TS70 languish.

This fall, London has been showing more interest in astronomy and I let him have the TS70 as a hopefully more user-friendly alternative to the Astroscan, which is a cool scope but can be a real PITA to get on target with.

The first problem is that although the TS70 has an actual dovetail bar, it is so ludicrously short and so far forward on the tube that it is almost impossible to balance the scope. For reasons that escape me at the moment, I have several spare dovetail bars lying around, so I grabbed the next larger one to put on the TS70.

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But there’s a problem: the bolts that hold the ludicrously short dovetail (LSD henceforth) on the scope are threaded into nuts inside the tube. You can see those nuts and bolts at the bottom of the tube in the middle distance in the above photo. But you can only see them because I had to remove the objective lens to get this picture.

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Well, in for a penny, in for a pound: I disassembled the whole damn scope. Here are the bits. The hex wrench set and screwdriver are mine, the solar film inside the lens cap (described here) is one of my hacks, but the rest is as it came from the factory. Only, you know, taken apart. From 12:00, the bits are:

  • the tube with the finder still attached;
  • three screws for attaching the focuser to the tube;
  • said focuser;
  • the black plastic dust cap from the focuser;
  • the LSD, its two hex bolts, and their nuts;
  • the two pieces of glass that make up the objective lens;
  • the retaining ring for the objective lens;
  • the dust cap (with solar film) for the objective lens, with the dew shield inside.

The dew shield slides off, and the retaining ring for the objective lens simply unscrews. There’s nothing else holding the two components of the objective lens in; once the retaining ring is off you can simply tilt the tube down and let them fall out–onto something soft (so they don’t get scratched), that isn’t your hand (so they don’t get smudged with oils). The focuser is held into the tube with the three screws, and the LSD is held on with the two bolts and their nuts. So there are really only five fasteners holding the scope together, or six if you count the objective lens retaining ring.

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So, about that objective lens. This is an achromatic doublet, meaning that it has two pieces of glass of different compositions (the ‘crown’ and the ‘flint’), to bring more than one color of light to focus at once.  In the above photo, the crown is on the left and the flint is on the right. They are different colors, but I’m not sure if that’s because of different light transmission or different coatings. Note the three little foil spacers on the flint, which keep the two lenses at the proper distance.

IF you ever disassemble a multi-element lens, it is extremely important that you keep the parts not only in the right order, but also facing the right way, or you are going to waste a lot of time trying different arrangements (and risking damage to the glass) until you discover how they go together. Better to just keep track of them as they come out.

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Next item: unless their edges are blackened, lenses suffer from internal  reflections, which cause reduced contrast at the eyepiece. Lots of cheap scopes and eyepieces have un-blackened lens edges, so whenever I take something apart, I blacken the edges. I use a sharpie, two coats, but I’m sure there are other ways.

Aaanyway, the retaining ring for the objective lens is almost always too tight when the scope ships from the factory, and simply unscrewing the ring and gently shaking the tube to settle the lenses is often enough to improve collimation. And that’s all I did here.

So how’d it work out? Last summer, I wrote:

The scope starts to pant around 40x and anything north of 60x is just bad…. Trying to achieve focus on planets is maddening. Jupiter goes from a vertical fan of red light on one side of focus to a horizontal fan of blue light on the other, and only sort of flirts with being a clean disk in between those extremes, at an infinitesimally tiny point that the rack-and-pinion focuser tends to shoot right past.

But Saturday night out at the Salton Sea, the reassembled Travel Scope 70 was like a brand new scope. Images were still pretty crisp at 67x with a 6mm Orion Expanse, and going up to 133x with a Barlow did not just add empty magnification. Here are my observations on different objects.

Polaris

At midnight, I split Polaris with the TS70 using the 6mm Expanse. I note this because In his review of the TeleVue 76 (an $1800 scope), Ed Ting wrote,

There was a time, not terribly long ago, when splitting Polaris was said to be a good test for a three inch scope. In today’s brave new apochromatic world, however, splitting Polaris is something of a joke.  Polaris is easy.  The double-double is easy.

That’s cool, but the TS70 is not an apochromat (a three-lens-element scope with better control of false color and therefore usually sharper optics than an achromat), nor is it a three-inch scope (2.75″ to be exact). So the fact that Polaris was cleanly split at relatively low magnification (67x) has to be a win.

Epsilon Lyrae

What about the double-double, aka Epsilon Lyrae? I Barlowed the 6mm Expanse to get 133x, which is where I run out of eyepieces and Barlows to increase the magnification on this scope. The northern member, ε1, was clearly elongated but not cleanly split, but ε2 was cleanly split. That’s a little nuts, because ε2 has a narrower separation (2.3 arc seconds) than ε1 (2.6 arc seconds), so it should be harder. I can think of several possible explanations, most having to do with the  fact that the ε1 pairs were lined up horizontally in the sky at 12:20 AM, whereas the ε2 pairs were lined up vertically:

  • the scope might have some astigmatism that is more pronounced horizontally than vertically;
  • my eyes might be more sensitive to vertical than to horizontal separations (I have no idea if this is true, but it’s possible. Maybe I should check some time.);
  • the separations were so seeing-dependent (even ε2 was not cleanly split all the time) that any unevenness in the atmospheric turbulence between me and the stars–say, the heat plume from a distant campfire–might have thrown things one way or another;
  • the more pronounced brightness difference between the ε1 components (magnitudes 4.7 and 6.2) compared to the ε2 components (5.1 and 5.5), although not normally a factor, might have made that one a tougher split since I was working at the hairy edge of what the scope and the conditions would support.

Anyway, since the closer pair of the double-double was cleanly split even under the less-than-perfect conditions Saturday night, I feel confident saying that this scope will split the double-double.

Jupiter

From my notebook:

1:50 AM. Jupiter in TS70 with 25mm Plossl (16x), just a bright spot. In 12mm Plossl (33x), a disk with two bands. In 6mm Expanse (67x), hints of more than 2 belts during moments of steady seeing, but bad seeing easily visible in image–Jupiter looks like it is on fire. Barlowed 6mm Expanse (133x): this is too much mag. No new detail, and previously seen belts and zones are harder to make out. No problem focusing using moons, though–I think problems are seeing, not scope.

3:57 AM. TS70 to Jupiter, in 6mm Expanse (67x, definitely more than 2 belts/zones showing now that Jupiter is higher in the sky. Planet is still visibly “burning” in the bad seeing. Three to four belts visible, meaning at least two different belts in addition to the bold equatorial belts, but hard to hold both extra belts at one.

Trapezium in Orion

Again from the notebook:

  • 25mm Plossl (16x) – 2 components (3 visible, but only 2 cleanly split)
  • 17mm Plossl (24x) – 3 components
  • 12mm Plossl (33x) – 4 components cleanly split

TS70 waxing gibbous moon 2013-10-12

Misc

Mars was a visible disk in 6mm Expanse, but swimming in the near-horizon murk near Regulus.

M81 and M82 easily visible in 25mm Plossl (16x), showing some detail in 12mm Plossl (33x).

M31, M32, and M110 visible in one field with 12mm Plossl (33x).

I spent some time on the moon, and snapped the photo above using a Canon S100 point-and-shoot and a 25mm Plossl. I flip-flopped it left-to-right and lightly sharpened it in GIMP, but didn’t mess with the brightness or color. It’s not an amazing image–a 90mm Mak will thoroughly spank this scope (proof)–but it’s not bad.

Conclusion

So, I have to revise my opinion of this scope. As supplied, I still have major reservations:

  • the tripod is wretched, and struggles to hold a small point-and-shoot digital camera stably, let alone a telescope;
  • the finder is a joke: too small to start with, then stopped down, and using plastic lenses to boot. But it makes a decent sight tube if you strip out the guts. London thinks the stripped version is the bee’s knees;
  • supplied backpack is okay, but no pockets inside or out, and only one partial divider inside (not that you’re buying this for the backpack, just sayin’);
  • eyepieces are nothing special and replacing them should be a top priority;
  • as supplied, my scope had two major problems: the LSD, which all TS70s ought to share, and badly miscollimated optics on this sample, which were easy enough to fix by completely disassembling the telescope and voiding the waranty. Also, focus is still a hairy procedure at high powers, and it is easy to overshoot best focus.

However, if you’re willing to buy or build a new mount and put in a little elbow grease, there is a surprisingly capable scope lurking inside this unassuming package–one that is capable of doing useful work on the observing field. Even with mostly plastic, jokey accessories, this scope is still a decent deal, although I shudder to think about the many unfortunate users who try to use the scope on the supplied tripod.

I note that according to the commonly-used “50x per inch of aperture” rule of thumb for max magnification, a 2.75-inch scope ought to be good up to 138x, which is pretty darned close to what I was working at (133x). So to be fair all I have established here is that the scope is adequate, according to one widely-used and fairly conservative guideline. But it’s so much better now than it was last summer–an actual observing tool, not just a toy. And that’s a win.