Archive for October, 2013


Observing tip: make a comparison chart for your eyepieces

October 16, 2013

MJW eyepiece comparison chartSherlock Holmes once exclaimed, “Data, data, data! I cannot make bricks without clay!”

I often feel the same way at the eyepiece. The more I know about what I’m looking through, and what I’m looking at, the more I understand what’s going on and can make meaningful evaluations and comparisons. At a minimum, I like to know what magnification I’m working at, and it is often helpful to know the true field of view (TFOV) and exit pupil (the width of the beam of light entering my eye). So I made a table with all of that information, for every combination of eyepiece and telescope in my inventory, and I keep it on a clipboard with a few other odds and ends.* So if I’m using a 21mm Stratus in my Apex 127, I don’t have to stop observing and do long division to work out the magnification.

* Single-sheet all-sky maps of the Messier and Caldwell objects (from here and here), often a tear-out map of the moon or the Milky Way from S&T, and the logbook for whatever project I’m working on.

As you can see, my table is a pretty bare-bones affair. I didn’t even give it a title,  just left it as “Sheet 1”. And when I got the C102 last week, I just wrote in the additional column by hand. But it’s a crazy useful thing to have along, and if you haven’t made one for yourself, I recommend it.

How do you calculate all this stuff?

Magnification is telescope focal length divided by eyepiece focal length. So in the XT10 (f/l = 1200mm), the 14mm ES82 gives a magnification of 1200/14 = 86x.

True field of view is apparent field of view divided by magnification. It’s important for star-hopping and celestial navigation; if you know that a certain object is two degrees west of a given star, that’s two eyepiece-fields if the EP gives a one-degree field. The ES82s have an 82-degree apparent field, the ES68 and Stratuses have 68-degree fields, the Expanse has a 66-degree field, and the Plossls all have 52-degree fields. In the same example listed above, the 14mm ES82 in the XT10 gives a TFOV of 82/86 = about 1 degree (0.95 to be exact).

Exit pupil equals the diameter of the scope’s objective lens or primary mirror divided by magnification. That’s pretty much what magnification is: taking a wide beam of light with a small image scale and turning it into a narrow beam of light with large image scale. To keep using the same example, in the XT10 (250mm diameter) the 14mm ES82 give an exit pupil of 250/86 = 2.9mm.

A lot of people, myself included, find that eyepieces become a lot less comfortable to use when the exit pupil gets under 1mm. In contrast, large exit pupils are very comfortable because you can move your eye around a bit without losing the light beam. Most veteran deep-sky observers recommend an exit pupil of about 2mm as the optimum for picking out faint details. This is explicitly a trade-off between brightness and image scale: lower magnifications offer a brighter image but smaller image scale; higher magnifications give a larger image scale but spread out the light so the image is dimmer. The only way to beat that trade-off is to move up to a bigger scope, which will let you have a brighter image at a larger image scale. That’s why aperture matters.


Revenge of the Celestron Travel Scope 70

October 15, 2013


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.


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.


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.


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.


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.


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.


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


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.


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.


Observing report: Night of the Refractors

October 14, 2013


London and I were back at the Salton Sea this past Saturday night (Oct. 12-13). It was our first time there  since my accidental Messier Marathon back in March. In between times it has been too darned hot to go camping in the desert. It was good to be back.

C102 at Mecca

The  big news was that I was rolling with a new scope: a Celestron C102 f/10 achromatic refractor, one of the “screaming deal” scopes from this post. I put it on the SkyWatcher AZ4 (= Orion VersaGo II) alt-az mount where my Apex 127 Mak usually rides. The included dovetail on this scope is too small and too far forward to balance well with an optical finder and heavy eyepieces, so I sprung for the Explore Scientific tube rings and dovetail kit. That was a pretty darned good deal; tube rings alone for a 4-inch scope run $30-40, and a decent-length dovetail is another $15-20, but the ES kit has both for $45, plus a very convenient carry handle opposite the dovetail bar. With the rings in place I could mount my StellarVue SV50 as a finder, and I was ready to go.


I also brought along the Apex 127 in case I felt like a change of pace, and because it takes up almost no room (which is one of the reasons I got it in the first place). But I was having too much fun with the C102 and the Apex 127 never made it out of the case. At some point I’ll have to do a detailed comparo between the two scopes, but Saturday night I was just out to have a good time.

We also had along the Celestron Travel Scope 70, which London is using in the photo above. I had completely disassembled and reassembled that scope, and after London went to bed at 10:00 I divided my time about equally between the C102 and TS70. Partly I wanted to put both scopes through their paces, and partly I just wanted to hop around the sky, checking in on friends new and old.

C102 1st quarter moon 2013-10-11

I will have to do a full-on review of the C102 at some point. For now, suffice it to say that it is a very nice scope. Image brightness and contrast are both excellent; for someone who has spent most of his time observing with reflectors and catadioptrics, this does not feel like a 4-inch scope. On most objects I could have been fooled into thinking I was looking through a 5- or even 6-inch mirror scope.

Grain of salt: I didn’t actually go back and forth between this scope and 5- or 6-inch mirror scope, although I plan to do that in the future. I’m just saying that as someone who has spent a lot of time looking through smallish Newts and Maks, this scope felt like it punched above its weight. I was worried that I would feel like I was missing out by taking such a small scope as my main instrument. But I was having so much fun with it that I stayed up nearly to dawn–there were always two or three more things I wanted to check out.

The photo above is not from Saturday night but from my driveway on Friday night, when the moon was exactly at first quarter. I flip-flopped it left to right and lightly sharpened it in GIMP, but didn’t fiddle with the brightness or color. There is some false color, most notably along the limb of the moon and on bright planets like Jupiter, but I didn’t find it objectionable. YMMV.

Salton moonset composite 2013-10-13

I think this is my new favorite moon scope. The image is so contrasty, details just pop. I would put in the 6mm Expanse (167x), watch the moon drift across the field of view, and pretend I was an astronaut. I also sketched a really nice catena (crater chain) in the northeast quadrant of the crater Deslandres. You can see it on the right in this LPOD image, opposite the smaller crater Hell that sits in the western part of Deslandres. If this catena has a name, I haven’t discovered it yet; feel free to enlighten me in the comments.

The moon set precisely at 1:00 AM. As you can see from the above composite, the seeing was not fantastic, especially near the horizon. Stars were visibly twinkling below about 45 degrees elevation.

After the moon set, it was like a whole new sky. The Milky way fairly blazed, and the sky was so full of bright stars that it was almost overwhelming. I was about as happy as I have ever been.


I spent some time observing near the zenith. This can be a pain with a long-tube scope like the C102. You can extend the tripod legs to put the eyepiece at a convenient height, but then you’re futzing with tripod legs all night long, which I loathe doing (another reason I got the Apex 127 was that I can go from horizon to zenith at one tripod setting). I remembered David DeLano saying that he often sits on the ground to observe at high angles, and that led to some experimentation. I found that my range of comfortable sitting eyepiece heights overlaps with my comfortable kneeling eyepiece heights, so I put out a camp pad for my knees and a folding chair for my elbows and voila. Someday I will build or buy an adjustable observing chair, but until then, this will do.


I have a couple collapsible camp chairs. They are great for stashing eyepieces when I’m really rolling, because I don’t have to worry about them falling over and rolling off onto the ground like I would with a table. I keep my eyepiece case on a picnic table, well back from the edge, so there’s no real opportunity to knock it over.

Now that I have some nice Explore Scientific widefields, I have become a bit of an eyepiece snob. Early in the evening I was sharing views with London and people from a nearby campsite so I started with my “second string” of Orion Stratuses and Plossls, just in case. Sound like a jerk move? Just wait until some kid–or a grown-up relative, in my case–says, “Hey, do I look here?”, and stabs the eye lens of your favorite eyepiece with a greasy fingertip.

But I guess the joke’s on me because the views through the second string EPs were so good that I never got around to hauling out the ES models. My lineup for Saturday night included:

  • 32mm Plossl (31x, 1.7 degree true field of view) for lowest magnification and maximum true field in a 1.25″ EP (I don’t have a 2″ diagonal yet so my 38mm AstroTech Titan, which would go even lower and wider, stayed home);
  • 25mm Plossl (40x, 1.3 degrees);
  • 21mm Stratus (48x, 1.4 degrees)–comparing this to the 25mm Plossl illustrates one of the nice things about widefields: you can get higher magnification (bigger image scale) and a larger true field (more actual celestial real estate) at the same time;
  • 13mm Stratus (77x, 0.88 degrees);
  • 12mm Plossl (83x, 0.63 degrees);
  • 6mm Expanse (167x, 0.40 degrees).

You would think that the Stratuses would put the 25mm and 12mm Plossls out of business, since they give basically the same or better magnification and a bigger true field. But the Stratuses are quite a bit heavier than the Plossls and required rebalancing the scope. So I was either in Stratus mode or Plossl-and-Expanse mode, and over the course of the evening, the cheap eyepieces won out in terms of convenience.

Also, frankly, f/10 is a pretty forgiving focal ratio. With a light cone that shallow, practically any eyepiece is going to do well. The only reason to prefer widefields is for their actual wide fields, and not to help control aberrations from the scope itself. I did note that the difference in apparent field of  view was immediately obvious when I bounced from the 52-degree Plossls to the 68-degree Stratuses. Oddly, I never noticed it with the 6mm Expanse (66 degrees), but I think that’s because I only used the Expanse to power up on the moon, planets, and double stars, where I was always fixated on whatever was at the center of the field.

My favorite observations of the night, in rough chronological order:

Double Cluster and Stock 2

I have waxed poetic about the Double Cluster before (you can find it here). It’s pretty close to a larger, sparser cluster called Stock 2, which is shown is most atlases, including the Pocket Sky Atlas. But I had never noticed the chain of bright stars that connects Stock 2 and the Double Cluster, and I had also not picked up the stick figure in the center of Stock 2. Here’s a photo by Doug Scobel of the University of Michigan Lowbrow Astronomers (borrowed from here) that shows what I mean (lower image GIMPed by me):


I revisited the Double Cluster periodically throughout the night. Right after dark it was the second thing I looked at, after the moon, and it was my last object before I packed up at 5:40 AM. Probably my best view was at 3:00 AM, when I wrote:

Nicely framed, mesmerizingly beautiful. I see at least two red stars in more easterly cluster, NGC 884. NGC 869 is at end of chain to Stock 2. All at 31x.

I still do plan to get into astronomical sketching, and when I do, I reckon the Double Cluster will be one of my first targets, if not my very first.

Andromeda Galaxy (M31) and satellite galaxies (M32 and M110)

Also about 3:00 AM, immediately before the Double Cluster observation above:

With 32mm Plossl (31x), all three galaxies fit in field, with dust lane popping in and out in averted vision.

I should mention that M31 itself was too big to fit into the field of view of my lowest-power eyepiece; with the core of the galaxy centered in the field, the edges of the spiral arms went out of the field in both directions. M31 is so darned big that unless you have an instrument with a 3-degree true field, you just can’t see all of it at once. Corollary: if you can fit the galaxy into a smaller field of view, then you’re not seeing all of it, which is sadly the case under even moderate light pollution. The core will punch through even vile city lights, but the spiral arms just die out.


Best view was at 5:00 AM, with the 12mm Plossl (83x):

Bands not quite lined up with moons. NEB [North Equatorial Belt] seems narrower and better defined than SEB. Several distinct belts to north, single broad ?temperate belt to south. Max detail at this mag–at 187x, seeing is too mushy.

Zodiacal light

I stopped about 5:10 for a biology break. Walking back to the telescope, I was stopped in my tracks by what seemed to be a second Milky Way: a broad band of light stabbing up from the eastern horizon, past Mars and the Beehive (M44) and reaching almost to Jupiter, which was by then high in the sky. It took me a minute to realize that this was the zodiacal light: the cumulative effect of sunlight reflecting off of countless grains of dust in the ecliptic plane of the solar system. The name “zodiacal light” comes from the fact that this light is always found along the zodiacal path traced by the sun, moon, and planets, as it must be, since almost everything in the solar system orbits in roughly the same ecliptic plane (comets excepted–they can come in from any angle, and the fact that they do so was one of the first clues to the existence of the Oort Cloud).

The Gegenschein, which I saw at the 2010 All-Arizona Star Party, is another manifestation of the same phenomenon. Basically, the Gegenschein comes from “full” dust grains exactly opposite the sun in the sky, and the zodiacal light comes from “crescent” or “gibbous” dust grains at other angles. Apparently under the very darkest skies, the Gegenschein can be seen as a bright patch in an arc of zodiacal light that stretches overhead from horizon to horizon. I have not seen that, but it’s on my bucket list.

Anyway, given how bright the zodiacal light was Sunday morning, I think I must have seen it many times before and simply not recognized it. I will keep my eyes peeled in the future.

M81 and M82

Anytime I’ve got more than one bright galaxy in the eyepiece, I’m a happy man. These two were nicely framed in the 32mm Plossl (31x). Using the 12mm Plossl (83x), the gravitationally-tortured M82 showed some hints of detail in averted vision.

The Odd Couple–M97 and M108

Probably my favorite pair of Messier objects. M97, the Owl Nebula, is a planetary nebula, a single dying star, about 2000 light years from Earth–right next door, cosmically speaking. M108 is a spiral galaxy in the Ursa Major galaxy cluster, about 46 million light years away, roughly the same size as the Milky Way and containing perhaps half a trillion stars. So one of these things is 23,000 times farther than the other one, and several hundred billion times more massive. If M97 was a ping-pong ball held at arms length, M108 would be a frisbee half a mile wide, located 8.5 miles away. But they look about the same in the telescope in terms of size and brightness, and you can frame them in the same low-power field of view, as I did at 5:27 AM on Sunday.

(Incidentally, I just discovered that Google will convert megaparsecs to light years–handy!)


After visiting M97 and M108, I had a quick peek at Mars. The red planet is very distant right now, on the opposite side of the sun from us, but it was visibly a disk and not just a point even at low magnification. The disk was most clear at 83x in the 12mm Plossl, but the planet was just flaming in the lousy seeing and I couldn’t make out any details.

Speaking of Mars, our rover Opportunity landed in January, 2004, and is therefore more than nine-and-a-half years into its 90-day mission. Not bad.

After Mars I briefly revisited the Double Cluster, but I could tell that my eyes and brain were no longer operating at anything like peak capacity. So I closed everything down and got a couple of hours of rack. The photo above shows my super-fancy telescope protection system. There are dedicated protective covers for telescopes that will work in rain, sleet, and hail, but hell, if conditions get that bad I will pull the scope inside the car. I didn’t just pack it up because I wanted to do a little birding with it in the morning.


We  did spend some time birding, and then while London got the campfire going, I started packing up. I do have a nice padded case for the telescope en route from Amazon–this one, recommended by David DeLano–but it’s not here yet so I used the trash bags and the packing materials the scope came in.


London stayed busy with the Travel Scope 70, which had gotten a workout overnight on the moon, Jupiter, and the deep sky. I have another post coming about the reborn TS70–stay tuned.


One last thing: Reese’s peanut butter cups make fantastic s’mores, and if you have any left over, they are great in pancakes, too.

All in all,  it was a fantastic night, one of my best–and longest–nights of stargazing of all time. At 3:30 I stopped observing to sit at one of the picnic tables and eat a banana. The stars were so bright and the sky was so full of stuff to look at. When I got back to the telescope, I scrawled in my notebook, “Nights like this make me wonder why I bother to observe anywhere else.”


Two more screaming deals on scopes

October 10, 2013

C102 OTAFirst up, the Celestron C102, a 4″ f/9.8 achromatic refractor. This is available in a couple of guises. The scope itself, without mount or accessories, can be had from OPT and possibly a few other places for, as of this writing, $119.95. It was even cheaper this summer–at one point, OPT had a package with the tube, a 2″ mirror star diagonal (typically an $80+ item), and some other bits for around $60 $80.* At that point you’re basically getting a solid deal on a 2″ diagonal and getting a 4″ scope for free. Did I pounce? No. But only because I am a moron. Now the packages with diagonals and eyepieces are sold out, and only the bare OTAs are left, and even they will probably not be around much longer. From what I hear, these are factory overstock and once they are gone, they’re gone.

* Update: David DeLano wrote in to clarify the different deals, and put the current one in perspective:

The C102GT bare scope was $60.  Both the 2” and 1.25” package were $80.  All were PLUS shipping.  The 2” package came with the diagonal (only).  The 1.25” package came with diagonal, EPs, and finder (I think I have that correct – Doug bought that one).  I think you said you got free shipping [I did–MW], so in reality, you only paid $15-20 more than what Doug and I bought ours for, though you didn’t get a “package”.

C102 Nexstar mount

I don’t think that there is any danger that the C102 is going away entirely, though. The Nexstar version, with Celestron’s intro-level GoTo handset and motorized mount, is available all over the place. Hayneedle has it for $299. At one point it was selling at Costco for $199, which is staggeringly cheap. That’s where Terry Nakazono got his, which I got to see and look through at the 2012 All-Arizona Star Party. Costco doesn’t seem to have them anymore, or at least they are not listed online, but (a) it might be worth going to your local store to see, and (b) possibly they will be back around Black Friday/Cyber Monday.

Update the Second: Also from David DeLano, news about this year’s “Costco Scope”:

I stopped by Costco today.  The scope this year is a Celestron 90GT.  F/l is 910 (box says F/10).  It comes on a NexStar mount, likely the same one as last year.  The drawback last year was that the NexStar mount was a bit undersized, whereas it should be fine for the 90GT.  Price is $179.99.

The C102 has gotten positive reviews, even earning a coveted “highly recommended” from Ed Ting. That review is mandatory reading if you are even remotely interested in this scope.

I did eventually pounce, springing for the bare OTA version, whose arrival on Tuesday was eerily coincident with the onset of rainy weather. So no first light report yet. But the scope is very big, and seems quite well put-together. I’m anxious for clear, clean skies so I can see what she can do. I note that this is the first telescope model that all four members of what I now think of as the “10MA gang”–David DeLano, Terry Nakazono, Doug Rennie, and myself–have owned. After I’ve clocked some photons with the scope I will write down my own thoughts, and then maybe I will solicit independent reviews from David, Terry, and Doug, and post a giant quadreview (assuming everyone wants in!).

Update the Third: I did get my scope out under dark skies–observing report coming soon–and although a full review will have to wait, it is a nice instrument and a solid deal. I recommend it, although for $60 more the 90GT SLT at Costco is worthy of serious consideration.

Meade NG60-SM

Next item: another achromatic refractor, the Meade NG60-SM, a 60mm f/11.7 scope with tripod, diagonal, eyepieces, and finder, list price about a hundred bucks, currently $24.99 plus shipping. Normally I might hesitate about recommending a “department store” scope like the NG60, but Terry gave it a solid review on CN. Now, if you’re not a 10MA regular, you gotta take that with a grain of salt–not because Terry is a bad observer but precisely because he is such a good one! At this point he’s tracked down 500 or so galaxies, almost all from light-polluted areas, and all using small scopes of 6″ or less (most were observed and sketched with scope of 4″ or less). So he is an expert at squeezing every last ounce of performance out of small scopes, and if you’re not an expert at that (as I am not) you won’t see as much through this scope as Terry does. But you can get there with practice–even Terry was a n00b once–and you’ll see a lot and learn a lot along the way.

With all that said, I don’t think that the NG60 would make a terrific first scope for most people; something like the Orion FunScope (76mm, ~$60) or SkyScanner 100 (100mm, ~$110) would definitely gather more light and would probably be easier to use. But I am pretty confident that the NG60 is the best $25 scope currently available, and possibly the best $25 scope ever offered. I am tempted to buy several and stash them in the closet for friends and relatives.

For a final word on the worth of a 60mm telescope, or any small telescope, I can do no better than to quote Tim2723 on CN, who wrote:

To focus on a bright star and find it set in a field of faint ones you never dreamed existed. To see Jupiter as a tiny gray circle with two dim bands across its face; its four pinpoint moons laid out as Galileo saw them. To view the Moon before it was a destination; when it was the great domain of the backyard sky gazer. To strain at the tiny disk of Saturn against a circle of black velvet and for a fleeting instant watch its oval shape resolve into a ring. To behold wonders that the sea of humanity passes by every night without a glance. To stand alone in the dark and weep before the awesome grandeur as the veil of eternity parts in a tiny circle of glass. To live in the sure and certain knowledge that there are things greater than yourself.

That’s what a 60mm telescope can show.


Observing report: All-Arizona Star Party 2013

October 9, 2013


Last weekend London and I headed out to Arizona for the All-Arizona Star Party. This was our third such event–we also made it out in 2010 and 2012. London was more excited than usual about the actual stargazing. We took along his Astroscan, 50mm spotting scope, and 7×35 binoculars, and he used them all. He was also curious about the Travel Scope 70 so I tossed it in the car on a whim–this proved to be a fateful decision. As for myself, my back was acting up yesterday so I skipped the XT10 in favor of the Apex 127/SV50 combo, plus 10×50 Nikon bins.

We rolled in just after sunset. As usual, we walked around and said hi to the neighbors. This paid off later on when one guy invited us over for a look through his 14″ StarMaster dob. We looked at the Saturn Nebula (NGC 7009), which was not detailed but visibly blue, and at the Double Cluster (NGCs 869 and 884), which was simply stunning.


The summer Milky Way was standing up straight from the horizon so I set up the Travel Scope 70 and started showing London the Messier objects in Scorpio, Sagittarius, and Scutum. His favorite was the M24 star cloud, which is fine by me, because it’s one of my favorites, too (find it yourself here).

The seeing was not great–lots of twinkling stars. But transparency was good. After London sacked out I got in a good four and a half hours of chasing Herschel 400 objects with the Apex 127, and logged 17 new ones. I also looked at scads of Messiers en route, probably three or four dozen in all.


Now, here’s a weird thing. Maybe it’s partly to do with the skies out there being so good, but every time I looked through the SV50 or TS70 I thought, “Wow, bright!” and every time I looked through the Astroscan or Apex 127, the view seemed disappointingly dim by comparison. Last year when I first started playing with the TS70 I was also blown away by the brightness and crispness of the view (at low mag, anyway). It can’t only be a function of f ratio because the Astroscan is an f/4 and the f/6 TS70 was smoking it. Nor is it anything to do with collimation–the Apex 127 was splitting double stars down to the limit of the seeing, and star-tested practically perfectly, whereas I suspect the TS70 is way out, given how poorly it takes magnification (irritatingly, I didn’t think to just star-test it).

So, I am wondering: is this how one gets to be a refractor guy?

Go home, cactus. You are drunk.

Go home, cactus. You are drunk.

Brief, possibly amusing note — Google turns up the following numbers of hits for these terms:

  • refractoritis – 6040
  • refractor guy – 5300
  • refractor weenie – 296  <– often self-described!

I’m the jerk

October 8, 2013


For various complicated reasons, I had to take a cab home from work tonight. The cabbie mentioned that we were supposed to get rain soon. I took this as good news: even the cacti in my front flowerbed are looking a bit peakid, and the SoCal skies are always cleaner and more transparent after a rain. I asked when the rain was due, and he said maybe as early as tonight. That is not fantastic news, because I had hoped to watch Algol go through its minimum tonight and thus check off the 100th item on the AL Urban Observing Club.

When I got home, I learned why the rain is coming in tonight. A long skinny box from Oceanside Photo & Telescope was waiting for me. In other words, the New Scope Curse has struck again. So if you’re a SoCal stargazer and you’re wondering why, after a fortnight of  clear skies, we’re having rain: I’m the jerk.

I have some catching up to do here, but not a ton. Basically since March I have been out of stargazing, except for a quick peek or outreach here and there. In addition to teaching, which goes on every year, I’ve been shepherding a record number of papers (for me) through the publication process, writing a book, and gearing up for my tenure application. To be honest, it hasn’t been super fun. Like Bilbo, I feel thin, like jam scraped over too much toast. The lack of stargazing is just a symptom of that larger problem.

But things are looking up, metaphorically and literally. I will be in the anatomy lab until the last week of this month, but I have given my last lecture and written my last exam question for this year. My tenure application is almost done, and so is the book, which is good, since the former is a little past due and the latter is due at the end of this month.

And I have rediscovered something that I had forgotten for too long, which is that stargazing is therapy for me. In the middle of town, it puts me in touch with nature; in a career that keeps me on the computer for most of the day, it gets me off the grid (even if only by twenty feet); amidst the crowds and busyness of life it is a little space in which to be alone and at peace. I need to remember that, at least for me, a telescope is a device for seeing farther both inwardly and out.

I will have more to say soon about my return to stargazing and the contents of that preciptation-precipitating box. For now, I am just glad to be back.

The photo at the top is from our Arizona vacation in May, on the Sunset Crater/Wupatki Ruins loop road. That’s 300-million-year-old limestone on the right and probably 300-year-old basalt on the left. In fact, the likelihood of this road being destroyed by a future lava flow is pretty good. I’m still a fan.