Archive for the ‘Eyepieces’ Category

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Observing Report: more Messiers at the Salton Sea

March 21, 2017

I went to Mecca Beach again Saturday evening. Like my run at the end of February, it was a solo mission, decided on at the last minute. I made up my mind in the mid-afternoon and I emailed a few folks to see if anyone was interested, but that proved to be too little notice (not surprisingly).

I got a late start, didn’t arrive until about two hours after sunset, and there was a cloud bank to the west, so I missed out on all of the early evening Messiers. I skipped right over the winter objects, having spent the last 6 weeks observing them repeatedly with a variety of instruments.

Gear

I’m flying to Texas this weekend for a Messier Marathon star party – more news on that soon – and I’m taking the Badger along. I’ve flown with little Maks and with an AstroScan once, but this will be my first time flying with a refractor. I’ve had this trip in mind for a while – it’s why I was so excited to find that the Badger would ride securely and comfortably on my Manfrotto CXPRO4 plus DwarfStar rig, because that is an eminently flight-worthy mount and tripod combo. BUT the previous testing was just a short session in the driveway. I was curious to see how the Manfrotto/DwarfStar/Bresser setup would fare under semi-realistic conditions, on an extended observing run at a distant site.

I was also testing eyepieces. I want a travel setup that will be lightweight and low hassle, but that will still cover all the things I’m likely to want. My prime mover is the 28mm RKE. It is simply delightful and gives a bright view of a wide swath of sky. Next up is the Celestron 8-24mm zoom eyepiece, which covers most of the useful magnification range for this scope (19x-57x). I used this eyepiece a lot right after I got it. Then I was off it for a while – I went through a phase of doing a lot of high-power work with my Apex 127 and C80ED, and I thought (and still think) that the Celestron zoom was just a hair less sharp than the best of my non-zoom eyepieces, particularly the Explore Scientifics. However, my eyes are now the weakest link in the optical chain, even with glasses. So although I don’t get super-sharp pinpointy star images anymore (or at least, not until I get new glasses), I also don’t worry too much about whether my eyepieces are 100% sharp or only 97%.

I also auditioned some possible third players: the 32mm Plossl, just in case I needed more true field than the 28mm RKE will give; the 5mm Meade MWA for ‘high-power’ work (still only 92x); and the 2x Shorty Barlow. It turns out that I don’t need any more field than the 28mm RKE gives, so the Plossl is staying home; the MWA is nice but big, and not worth the bulk on this trip; and my Shorty Barlow has ever-so-slightly misaligned barrel pieces, so it won’t sit all the way down in the focuser. I’d noticed this before, but it didn’t bother me because all of my other eyepieces would come to focus anyway, but not, it turns out, the Celestron zoom. So the Barlow is staying home, too, and I’m planning to roll with just the 28mm RKE and the Celestron zoom.

Star Testing

I spent the first hour on just four targets: the Trapezium in Orion, the Pleiades, Jupiter, and Polaris. I looked at the Pleiades just to see them before they went down into the cloud bank over Palm Springs. The other three targets were to test the scope and the skies. The seeing was a little better than it has been for most of this spring, but still only so-so. The Trapezium was bouncing around too much for me to resolve the E and F components, although I suspected E a couple of times.

Jupiter looked a lot better than it has so far in this scope. I think that was partly a little better seeing, and partly the result of having collimated the scope. As I mentioned in the last post, the view of Jupiter at 92x was mesmerizing, with finely-divided belts and zones resolved all the way to the poles. I was using the 60mm aperture mask to knock down the CA, and that might have helped with the seeing and with other aberrations.

When I had stared at Jupiter for about 20 minutes, I removed the aperture mask and did a proper star test on Polaris. I’m not an expert at star testing but I know a little, and I have a copy of Suiter’s book, Star Testing Astronomical Telescopes, on loan from a friend in the club. I sketched the results inside and outside of focus and compared them to the diagrams in the book when I got home. The scope has about 1/4 wave of spherical aberration. That’s not great – it’s flirting with being not diffraction-limited, and it helps explain the scope’s so-so performance on solar system objects and double stars. On the upside, the perfectly-concentric diffraction rings confirmed that the scope is now in good collimation.

Binocular Messier Hunting

The best sky conditions of the evening were in the hour on either side of midnight. The cloud bank to the west was still there, but it had retreated down near the horizon. Transparency was as good as it was going to get. Lying down in a lounge chair and looking up naked-eye, I could make out sixth-magnitude stars at the zenith. After spending a good chunk of time at the telescope looking closely at a handful of objects, I was ready for a change of pace. I grabbed the 7×50 binoculars that came with the Bresser Comet Edition package and hopped in the lounge chair for a Messier tour.

I started with some galaxies in Ursa Major. M51, M81, and M82 were all easy, as were M94 and M63 in Canes Venatici. Then I jumped over to Corvus to pick up M68 and M104. After that I went to Coma Berenices and spent a while just staring into the Coma star cluster. It’s a true open cluster, and it looks huge because it is only 288 light years away. That’s farther than the Hyades (~150 light years), but closer than the Pleiades (380-440 light years, depending on the source), and the size of the Coma cluster is nicely intermediate between those two as well.

My first Messiers in this area were the globular clusters M3 and M53. Both were easy catches, and M3 was so bright I had to look twice to make sure it wasn’t a star. Seeing them in binoculars brought back fond memories of the very first time I ever observed them. It was the spring of 2008, and we were still living in Merced. I was on a backyard campout with London, who was only 3 1/2 years old. We were using my old dome tent, and as soon as London went to sleep I poked my top half out onto the grass and did some binocular stargazing. That was the first time I ever saw M3 and M53 with my own eyes.

My next target was the galaxy M64, and it was bright and obvious – so much so that it seemed to pop out from the background, the way that planetary nebulae sometimes do. M65 and M66 were not so pronounced but they were still easy prey. M95, M96, and M105 took a little more work and chart-checking, but I managed to bag them all. Later in the morning, after I’d gone back to the scope, I picked up the globular clusters M13 and M92, and the open clusters M6, M7, and M11.

I know that other observers have seen all 110 Messier objects with 7×50 binoculars – Jay Reynolds Freeman reports having done so in his essay, “Messier surveys“. I’ve seen all of the Messiers in my 15x70s and most of them in 10x50s, but I’ve never even attempted them in 7x binos. So I am working on a proper Messier survey with these 7x50s, and so far I’m up to 40 objects. Here’s my visual log – I’m highlighting objects in green as I observe them:

If you’d like a similar record sheet for your own observations, here’s a blank one:

A Varmint of the Skies

After an hour of binocular observing, I was ready for a stretch, and also champing to track down some of these objects with the scope. I had gotten through most of them with the scope, and I was about to make my assault on the Virgo galaxies when the moon rose.

I thought that contrast had dropped off a bit, and I was seeing fewer faint stars, and the rising moon made the reason clear: a high, thin haze had developed over most of the sky. Galaxies that had been dead easy in the binoculars just an hour before were now completely invisible in the scope. I missed out on M63, M94, and M101, and abandoned my Virgo galaxy hunt. I watched the moon rise through my binoculars, then I switched to double stars for a while. I’m not going to say much about that right now – suffice it to say that the results of my double star observing will be coming to a newsstand near you this fall.

After I’d done my double star ‘homework’, I was feeling very pleased. At the start of the evening I’d written down three goals for the session: “Messiers, double stars, chill”. With the first two activities done to my satisfaction, I was content to engage in the third. I spent more time looking at Jupiter and the moon through the scope, and a fair amount of time just sitting on a picnic table and looking up with my naked eyes. The haze had thinned out somewhat by 3:00 and I was just happy to be out under the stars. Although there were people camped just a few hundred feet from me, I had the place all to myself. Even the coyotes had stopped yipping and howling.

Back at the scope, I spent a while looking around in Lyra. My favorite astronomical axe to grind is that the “celestial sphere” compresses almost limitless space and time into what looks like a dome over our heads. As I put it in this article (and this even earlier blog post), I’m constantly trying to “shatter the bowl of the sky, to see space as space”. Lyra is a good area in which to do this, with objects as close as Vega – a scant 25 light years away – and as distant as the globular cluster M56, which lies 33,000 light years away. I’ll probably write a whole post about that soon.

Usually if I’m up that late at this time of year, I go through the “steam from the teapot” Messiers in Sagittarius and Scutum. But an unfortunate cloud was camped out in my way. I did pick up M11 in Scutum, and M6 and M7 near the ‘stinger’ of Scorpius, with both the binoculars and the scope. I also had a nice long look at the False Comet cluster near Zeta Scorpii. The False Comet is a fantastic object for binoculars and rich field scopes – or maybe I should say “a fantastic set of objects”, since it includes the open clusters NGC 6231 and Trumpler 24, and other bright stars in the Scorpius OB1 assocation, of which both clusters are members.

I’m up to 43 Messiers with the Badger. There are 3 objects that I’ve seen in the Bresser binoculars but not yet in this scope: M63, M94, and M101. And there are 6 that I’ve seen in the scope but not yet in the bins: M5, M29, M39, M56, M57, and M79. I’m not worried about the mismatch – most of the objects I haven’t seen in the binoculars because I just haven’t tried yet. Although I am a little nervous about my ability to distinguish the smaller planetary nebulae from stars at only 7x. Still, it’s a fun hunt and so far I’ve seen almost everything I’ve attempted. Here’s the visual tally for the scope:

I ended back in the solar system. I had a nice long look at Saturn a little after 4:00 AM, and at 4:15 I was gazing at the moon when I fell asleep. After a lifetime in academia, I’m very good at sleeping sitting up, and I didn’t realize I had drifted off until my eyebrow brushed the eyepiece, ever so gently. I think that’s the first time in almost a decade of stargazing that I have actually fallen asleep at the eyepiece. I called it a night, dragged the lounge chair around to the west side of the car where it would be out of the sun, and slept until almost 11:00.

Verdict? Well, the scope is no planet-killer. Doing the star test confirmed what I already suspected. But if I use an aperture mask and keep both the magnification and my expectations modest, it still delivers rewarding views of solar system targets. And it continues to be a fantastic wide field, low power scope for deep sky work. I was also happy to find that the light Manfrotto tripod and DwarfStar mount were more than adequate. I did have to let the scope settle a little at high power, but for Messier sweeping the whole rig just got out of the way and let me observe, which is what I had hoped for. Finally, although I had other eyepieces sitting in the rack, I spent almost the entire evening using just the 28mm RKE and the 8-24mm zoom. So as a test of my travel kit, the evening was a resounding success – and a heck of a lot of fun to boot.

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Finally – the Bresser Messier AR102S Comet Edition at the Salton Sea

February 26, 2017

ar102s-at-dawn

Sometimes life is cruel.

(Did I say cruel? I meant ridiculously First World cushy, where a grown man can afford nice toys and has the time to play with them and blog about it. But within the context of this grown man’s play-time blog, sometimes life is cruel.)

To wit: my Bresser Messier AR102S Comet Edition (still sans snappy nickname) arrived on Sunday, January 29, just a few hours late for the new moon observing run at the Salton Sea that Terry Nakazono and I went on the night before. Since then it’s been mostly cloudy here, with poor transparency on the nights it hasn’t been totally socked in, so I’ve been misusing the scope on bright stuff like the moon and Jupiter. And waiting not-so-patiently for a chance to get out to dark skies and do some wide-field, low-power scanning.

I actually did get about 45 minutes of semi-dark time with the scope a week ago. I was on dawn patrol up in the foothills and I spent some time in the summer constellations before the sun came up. The views were bright and contrasty, but all it did was whet my appetite.

Friday night I finally got the scope out under decent skies, for a decent amount of time. I decided pretty late to go to the Salton Sea – originally we had other plans, but Vicki and London were wiped out from a long week, and the forecast said that Friday was the last clear night for a while, all over SoCal. I didn’t leave Claremont until almost 7:00 PM, and with set up time after I arrived at Mecca Beach, I didn’t start observing until 10:00.

Gear

I was rolling pretty light. I wanted to test the Bresser reflactor/bino set as a package, so I used the AR102S on the came-with mount and tripod. I essentially always have binos out while I’m observing, so I used the 7x50s that came with the scope. That was a novel experience – I usually roll with 10x50s or 15x70s. This was my first time using 7x binos for serious deep-sky observations.

The only way I broke with the Bresser package was with eyepieces. I did use the included 20mm 70-degree a few times early in the evening, and I briefly tested the 10mm 70-degree that just came in, but my most-used set for most of the evening consisted of the 28mm Edmund RKE, both natively (16.4x) and with a 2x Barlow (33x), and the 8.8mm ES82 (52x and 104x).

28mm-rke-in-ar102s

A word about the 28mm RKE. It is simply the most comfortable eyepiece I’ve ever used. There are several factors that play into that. One is the long eye relief. Another is the magical floating stars effect, which is real, and impressive. Finally, there’s the wide exit pupil it gives, which in the AR102S is 6.2mm. That’s probably wider than my pupils go these days (same is true of the 7mm exit pupil of the 7×50 binos). Using binos or eyepieces with exit pupils wider than your own will go is usually not recommended. The extra light falls on the muscles of your iris, not on your retina, so your pupil becomes an aperture mask, stopping down the system to a smaller working aperture. You could get just as much light delivered to your brain using a smaller instrument or eyepiece. But there is one positive effect of using a “too-wide” exit pupil: you can move your eye around a bit within the light beam, without any falloff in illumination. So “too-wide” exit pupils are very bright – maximally bright – and very comfortable. And if a bit of light is wasted, oh well, it’s not like the cops are going to come for you.

One nice effect of swapping the 28mm RKE for the 20mm 70-degree is that they have close to the same true field of view of 2.9-3.0 degrees, but the RKE gives a much sharper image with fewer aberrations. Unsurprisingly, since it’s bending light from the same true field into a much smaller apparent field. Normally, a 45-degree AFOV would feel downright claustrophobic to me these days, but for some reason the 28mm RKE doesn’t bother me. I think it’s the magical floating stars effect – most narrow-fields (okay, anything south of 50 degrees) feels tight, like looking through a soda straw, because so much my field of view is taken up by the inside of the eyepiece barrel. But with the 28mm RKE, there is no visible eyepiece barrel, so although the AFOV isn’t actually that big, it feels much more expansive.

I did have one minor gear screw-up: I forgot my laser. I haven’t installed a finder on the AR102S. Same with the C80ED, except for one or two nights early on. When I really need help I lay a laser finder along a straight edge and use it to point to things in the sky. On the C80ED, there are a couple of buckles on the tube clamp that together form a de facto trough like the one I built for the SkyScanner 100. On the AR102S, the finder bracket serves the same purpose. But I forgot my laser. So I did what I usually do, just dead-reckoned it. I’ve gotten to the point where I usually don’t even have to sight down the tube, I can just sort of look up and aim the scope and get the target within a 3-degree circle. The AR102S will go wider than 3 degrees – a 32mm Plossl or 24mm ES68 will give 3.6 degrees, and my 32mm Titan 2″ will go to 4.88 degrees. But none of those eyepieces do their thing with the same panache as the 28mm RKE – at least in this scope. I did get out the 32mm Plossl just in case I needed a wider ‘finder’ eyepiece, but it never made it into the focuser.

Goals

I had a program in mind. Long-time readers will know that I’m a big fan of Jay Reynolds Freeman’s astronomy essays, especially “Refractor Red Meets the Herschel 400”. More relevant to this post is “Messier Surveys”, in which Freeman relates his habit of running through all the Messier objects with every instrument he gets his hands on, from 7×50 binoculars to a 14-inch SCT. Despite my Messier Marathon attempts, I’ve never kept track of which Messiers I’ve seen with which instruments. I’m certain I’ve seen them all with the XT10, and I’ve seen almost all of them with my 15x70s, but beyond that, I have no idea. So I decided that the best way to properly test the Bresser would be to start a Messier survey with it.

To be clear, I had no intention of attempting an off-season or mini Messier Marathon. I decided to just go until I got tired. I also was not a purist – I looked at plenty of non-Messiers along the way, including some I had never seen and wasn’t planning to observe when I started.

And in fact, I started with some non-Messiers.

Perseus

When I started observing at 10:00, plenty of good stuff was getting perilously low in the west. The western reaches of Cassiopeia were already down in the Palm Springs/Indio light dome. I started with the Double Cluster and Stock 2 – my first time looking at them with the AR102S. They were spectacular as always. Then I swept up through the Alpha Persei Association and followed the eastern ‘arm’ up to NGC 1528. The cluster was fully resolved at 33x, but I thought it was prettier at 16.4x, when the dimmer stars trembled just at the threshold of resolution. I also checked in on NGC 1545, which is a much less impressive cluster and a much tougher catch since it is dominated by a bright foreground star. But my favorite observation in this area was another OC, NGC 1513. I tried this one at a variety of magnifications and it always ‘popped’ a little more in averted vision, as previously unresolved stars swam into visibility. Not one of the sky’s stunning showpiece objects, but delicately beautiful if you have the time to tease out its secrets (and the skies – it’s not bright).

I hit M34 on my way out, and of course I stopped at the Pleiades, which were very nicely framed at 16.4x.

Orion and Vicinity

After all of that, I realized that I had to get a move on if I wanted to catch M79, the glob in Lepus, before it set. I hopped over to snag it, and visited Hind’s Crimson Star while I was in the neighborhood. It was a tiny red spark in the 28mm RKE.

The whole sword of Orion fits into the field of view of the RKE. The Trapezium was nicely broken out into four stars at 33x with the Barlow. I had a quick look at Sigma Orionis and scanned the Belt and the big OB association just off Orion’s western hip. M78 was delightful. Even at 16.4x, the two foreground stars were visible and distinct from each other and from the background glow, and the western edge of the nebula showed a more abrupt cut-off, which lent the whole object the feel of a comet.

Binocular Tours

Up to this point I had been using the 7x50s to trace my star hops in advance, but now I really started to run ahead. One thing about writing my deep-sky tour articles for Sky & Tel – I usually remember all the stops and I can run through them quickly anytime I’m out. In this case, I started at Sirius and followed the path of my December 2015 article down through Canis Major, across Puppis – with a side trip down to Vela that was not in the article – and into Hydra (for M48). Then I picked up where my tour from this March started, running northwest through Monoceros and northern Orion before ending in Gemini. Running through both tours took about 10 minutes, and I saw a lot and missed a lot more. Seriously, that stretch of the winter Milky Way is just ridiculous. You can swing your optics over it again and again and not pick out all there is to see.

Then I had a long break to rehydrate, eat a snack, and get into my cool-weather getup. I’ll have to write a whole post about that sometime.

ar102s-set-up-for-observing

After the break I went back through almost all of that with the telescope, in part just to see it all with more than 50mm of aperture. I noticed some Herschel 400 objects in Puppis that I had never observed, namely the open clusters NGC 2479 and 2509. Both were dim swarms of faint stars that were still not fully resolved at 52x, but very pretty. I had not noticed them in the binos, but after catching them in the scope I was able to see them when I went back with the 7x50s. I was comparing the two clusters in the binos when a meteor flashed through my field of view, which is always a cool sight. I spent about half an hour trying to catch the planetary nebula NGC 2440, and even hauled out Interstellarum to help me get on target, but I never got a definite sighting. I’m going to have to study that one and come back another time.  I did catch NGC 2438, the planetary nebula that is superimposed on M46 but only about half as far off as the cluster. It was obvious at 52x but I couldn’t separate it from the glow of the cluster at 16.4x. Needless to say, it didn’t show in the binos.

Roaming

By the time I was finished retracing my winter Milky Way tours, the Auriga Messiers were getting low in the west, so I hopped over to check them out. After that I hit M44 and M67 in Cancer. M44 was just perfect at 16.4x – everything nicely resolved, but still compact enough to look like a coherent object. The stars in that cluster always seem to fall into geometric patterns to me, as if they were laid out using a grid system that got erased the morning after creation. I can’t think of anything else in the sky that gives me the same impression.

I also popped up north, past Iota Cancri and over the border into Lynx, to check on NGC 2683, a surprisingly bright and easy Herschel 400 galaxy that I had previously only observed with binoculars. (Want to know more about this galaxy and its neighbors? See the April 2017 Sky & Tel!) Since I’d seen it with smaller-aperture binos under worse skies, naturally it was an easy catch for the AR102S.

After that I turned south, to Omega Centauri. Although I haven’t written about it yet, when Terry and I were at the Salton Sea last month, I spent a long time looking at the monster ‘glob’ – actually the exposed core of a dwarf galaxy that was cannibalized long ago by the Milky Way. It’s a favorite spring target of mine when I have a good southern horizon. From Mecca Beach there is a definite light dome from El Centro and usually some near-horizon haze in the southwest – directly over the water. But Omega Centauri culminates between that particular Scylla and Charybdis. Last month I spent nearly an hour checking it out, using naked eyes, binoculars, and several levels of magnification with the C80ED. I could just get the outermost stars to resolve at 120x, albeit in imperfect seeing. This time was worse – about the same lousy seeing, and slightly worse transparency. I didn’t get any actual resolution, but I could make out pronounced differences in brightness across the face of the cluster. I also had a look at NGC 1528/Centaurus A, the famous radio galaxy. I think it should be naked-eye visible under optimum conditions, but my conditions were not optimum. It was obvious in the binos and showed some detail in the scope.

Then it was on to Corvus to check in on M104 and M68. I also observed the planetary nebula NGC 4361, I think for the first time. It’s bright but small, and it turned out that I could see it at 16.4x, I just didn’t recognize it – I had to go up to 52x to confirm that it was nonstellar. I also visited M83 while I was in that neck of the woods. What a wonderful galaxy, so big, bright, and obviously elongated even at low magnification.

By now it was almost 3:00 AM and I was getting pooped. I finished in Lyra, with Epsilon Lyrae and the Ring Nebula, M57. I couldn’t split the Double Double. That might have been the scope, but it might have been the skies – by this point there was a steady breeze blowing right in my face when I looked east. I have had other nights where the seeing was so bad that Epsilon Lyrae would not split. I did notice some CA around those stars at high power, which probably didn’t help.

I decided to finish with M57, which was fitting since it was a chance observation of that nebula with the TravelScope 70 a few years ago that got me hooked on refractors. I wanted to recreate the feel of that surprising low-power observation so I left in the 28mm RKE. The whole southern end of the parallelogram fit very nicely into the 3-degree field, with M57 showing as a pale little dot. Then I realized that I had stopped the scope down to 60mm while I was playing with the double star and had forgotten to take off the aperture mask. So I got to do one of my favorite tricks – reach up and pull of the mask while I’m observing, and watch the sky get brighter in a hurry, as if all the lights out there suddenly turned on. The nebula had been obvious at 60mm – at full aperture it was so bright it almost looked stellar.

ar102s-at-mecca-beach

Tally

I ended the night having observed several double stars and 46 unique DSOs with the telescope, of which only 22 were Messier objects. Three were Herschel 400s which I believe I observed for the first time – those were the open clusters NGC 2479 and 2509 in Puppis, and the planetary nebula NGC 4361 in Corvus.

I’ll have a more complete review along soon, but the Bresser Messier AR102S lived up to its middle name – it is a superb Messier-catcher. Every Messier I attempted was not just visible but easy at 16.4x. Will be interesting to try it on some of the smaller, tougher objects like M76. I think this will be my Marathon scope this year.

Don’t take this as a full-spectrum endorsement. When I do post a full review of the scope, I’ll have both good and bad to report. It’s not a good all-rounder, not a good first or only scope. But what it’s built to do, it does quite well.

The biggest surprise for me was how much I could see with the 7×50 bins. I didn’t catch everything, but of the 46 DSOs I observed telescopically, 34 were also visible in the binos, and some of the rest I simply forgot to check (the galaxy NGC 2683 comes to mind). There were more DSOs that I saw in the binos but didn’t take the time to log, including shedloads of clusters in Monoceros. I don’t know if I will be able to complete a Messier survey with the 7x50s – I reckon some of the smaller planetary nebulae will prove my undoing – but I’m at least going to make the attempt.

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Get $5 off your first purchase from OpticalInstruments.com

February 21, 2017

Hey, I was temporarily without a 10mm eyepiece (long story) and I have been sufficiently happy with the Bresser 20mm 70-degree that came with my AR102S Comet Edition that I plunked down thirty bucks for the 10mm version (sale price, down from $50). It was only my second-ever purchase from OpticalInstruments.com (after the Bresser Spektar spotting scope a couple of years ago), but they rewarded my ‘ongoing support’ with this deal. You can use this link and unique code:

https://opticalinstruments-com.myshopify.com/?redeem=58abdb56bb070f0018560f59

to get $5 off your first purchase, and if you do, I’ll get a $5 kickback. As far as I know, there is no limit to how often this can be used by people making their first purchase there. So if you’ve been tempted by something at that store, here’s your chance to save a little dough. Happy shopping!

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The 28mm RKE in action

February 20, 2017

Still cloudy here, but we got a gap earlier this evening, a persistent sucker hole right over Orion, and I got a whole 10 minutes of observing in. I was using the Bresser AR102S Comet Edition and for eyepieces the 20mm 70-degree that came with it, and my new 28mm RKE from Edmund.

Both eyepieces will just fit in the belt of Orion, with Alnitak and Mintaka in the last 5% or so of the field on either side. So the belt turns out to be a good test of edge characteristics. The 28mm RKE is way sharper at the edges, by the way. You might think that its 45-degree apparent field of view would feel positively claustrophobic after the 70-degree field of the Bresser eyepiece.

But it doesn’t, because of the magical floating stars effect. It’s real! It’s one of the most arresting things I have experienced in almost a decade of observing. As your eye gets closer to the eyepiece, you begin to be able to see the image. As you move in until you can see the entire field, the point where the eyepiece barrel disappears from view coincides exactly with the point where you are far enough to see the field stop of the eyepiece. If you hold up right there, you see the image created by the eyepiece floating in space, with a thin ring of unresolved darkness around it, which if you back out a bit will be the eyepiece barrel, and if you move in a bit will be the eyepiece field stop. In either case, the eye relief is great enough that you can still see the rest of the scope in your peripheral vision, past the thin ring of darkness at the edge of the field.

I have never, ever seen anything like this. It is exactly as cool and immersive as the legends have it. I can imagine building a whole observing kit consisting of this one eyepiece and a series of Barlows of various magnifications.

Anyway, if you have been on the fence about this eyepiece like I was, just get it. It’s amazing.

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Me and the ‘Stig

February 19, 2017

This story started a few nights ago. I had been monkeying around with the AR102S, both at its native aperture and stopped down, and I decided to see how it compared to the C80ED. In particular, I wanted to compare the rich-field views of both scopes (such as they are here – I was observing from the driveway after all), so I was looking at the belt and sword of Orion. The results of that comparo were not very surprising – with it’s wider aperture and shorter focal length, the AR102S goes significantly wider and brighter, but the longer focal ratio and low-dispersion glass of the C80ED produce a better-corrected image.

What was not only surprising, but actively alarming, was that at low power I was getting ugly star images in the C80ED. Even in the center of the field, stars were not focusing down to nice little round points, but to crosses and shapes like flying geese. I wondered if my diagonal might have gotten banged up, so I swapped diagonals. The problem persisted. The scope will not reach focus without a diagonal or extension tube, and I don’t have an extension tube, so I couldn’t try straight-through viewing. Still, it was exceptionally unlikely that both of my good diagonals got horked in the same way.

I didn’t know what to make of that. I figured maybe the scope had gotten out of collimation somehow, and I was pondering whether to mess with it. It’s always been optically excellent and mechanically solid (overbuilt, in fact), and I was loathe to take it apart (as opposed to the TravelScope 70 and SkyScanner 100, both of which were crying out for disassembly).

Then a few days later I ran across this thread on CN, in which a guy was having the same problem I had. It sounded like it was more likely astigmatism (aka the Stig) in the eyes than in the telescope. Apparently it’s worse at low powers where the exit pupil is large, which makes sense – astigmatism is caused by having corneas that are out of round (football-shaped rather than basket-ball shaped), but as the exit pupils get smaller, the less of the cornea is involved in vision, and the more likely it is that the ‘active’ portion will approximate a radially even curvature.

astigmatism-of-the-eye

One commenter recommended making a little diaphragm between thumb and forefinger to stop down the exit pupil. I tried that, but it was awfully difficult to hold my finger and my eye all steady and in alignment. Then I had the idea of using a collimation cap from one of my reflectors. That stopped down the exit pupil to a 1mm circle, which made the image d-i-m, but the star images cleaned right up. Then I took away the collimation cap and tried the view with and without glasses, and the glasses also cleaned up the star images.

It wasn’t the scope, it was me. I have astigmatism, and it’s bad enough that stars look ugly at low power unless I wear glasses.

On one hand, that’s a big relief, because the C80ED scope has always been a rock-solid performer. Along with the Apex 127, it’s my reference standard for good optics. I was feeling a bit queasy at the thought that it might have gotten out of whack.

On the other hand, I now need to prioritize eye relief in my eyepiece collection. I have a bunch that are too tight to show the whole field when I’m wearing glasses. So I have some decisions to make.

That was the first major discovery of the night.

The second was that the AR102S can take 2″ eyepieces with the most minor tinkering. The 2″-to-1.25″ adapter at the top of the AR102S focuser drawtube screws right off. I had been worried that it might be permanently affixed, but when I tried turning it, it spun with remarkable ease. Once I had it off, I dropped in the 32mm Astro-Tech Titan, which is my only 2″ eyepiece, and the views were pretty darned good. Way wider than with any of my 1.25″ eyepieces, and pretty clean as well, although I need to a little more head-to-head testing on that score. Possibly the star images looked good because they were so small at only 14x.

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In any case, the 32mm Titan gives a significant boost in true field, from 3.6 degrees in the 32mm Plossl and 24mm ES68, to a whopping 4.88 degrees.

I don’t think there would be any advantage in going wider, at least in the AR102S. Astronomics seems to be out of Titans, but the equivalent 70-degree EPs are available through Bresser and Agena. The next step up would be a 35mm or 38mm, giving 13x and 12x, but those would push the exit pupil to 7.7mm and 8.5mm, and that’s just wasted light. At least in the AR102S – in the C80ED, longer 70-degree eyepieces would yield the following:

Focal length / magnification / exit pupil / true field

  • 35mm / 17.1x / 4.7mm / 4.1 degrees
  • 38mm / 15.8x / 5.1mm / 4.4 degrees

Either of those would be a good step up from the 3.7-degree max field that the 32mm Titan gives in the C80ED, without pushing the exit pupil uselessly wide.

Anyway, I’m just noodling now. The big news is that the C80ED is fine, I need to prioritize long eye relief in future EP purchases (and maybe thin the herd a bit?) so I can observe with glasses on, and the AR102S can take 2″ EPs after all.

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Unboxing the Edmund 28mm RKE

February 17, 2017

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Look what came in the mail today.

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Something small, in a gold box.

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An eyepiece wrapped in paper, and a rubber eyeguard.

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And here they are.

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That is a big honkin’ eye lens. And that’s why I got this eyepiece. The 28mm RKE from Edmund is legendary for its “floating stars” effect where the big eye lens, the sharply raked barrel, and the long eye relief combine to create the impression that the eyepiece has disappeared and the image is simply floating in space. I’ve never experienced this, because I’ve never gotten to look through one of these before. But the reputation of this eyepiece, illustrated by several glowing threads on Cloudy Nights (like the ones that follow), was enough to convince me to take the plunge:

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It didn’t come with a case, so I made my own out of an old prescription pill bottle. A little bubble wrap stuffed in the bottom and taped inside the lid, and I’ve got a nice padded case for free.

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And I need that case, because the new gear curse is in full effect. How does this eyepiece work in practice? No idea yet – with any luck, I might find out next Wednesday, when the clouds are finally supposed to part. I’ll keep you posted.

 

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What’s in my eyepiece case

January 9, 2017

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In the 9.3 years I’ve been stargazing, I’ve had three eyepiece cases. The first was a Plano tackle organizer with a thin layer of bubble wrap taped into the lid, which held half a dozen 1.25″ eyepieces. After that I got one of the cool foam-lined purpose-built eyepiece cases that Orion and everyone else carry, but that one didn’t last long – probably less than a year. The problem was that although it did a fine job of holding the eyepieces, it didn’t have room for all the other stuff I wanted to cram inside.

Then in 2012 or so I got the eyepiece case that I’m currently using, and the one that I’ll probably be using for a long time to come. It’s not bespoke – it’s a $20 Craftsman toolbox I picked up at Orchard Supply and Hardware. I think this particular model has been discontinued, but there is something almost identical on the shelves today, and there probably will be from now until the end of time (or at least civilization). This one is probably the current incarnation, and hey, it’s only 10 bucks and has a better latch.

The exterior doesn’t deserve much comment. I put my name on it, and its contents, mostly to make it clear to anyone who might find it among my stuff if they’re going through the garage looking for tools of the terrestrial variety. I don’t fully trust the single latch so I keep a zip tie run through the hole where the lock would go. The zip tie goes in the top shelf when the case is open.

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The top shelf, which is removable, holds my red flashlight, Astro-Tech dielectric diagonal (previously discussed in this post), eyepatch, Barlow, and quick-look and outreach eyepieces – various Plossls, the 6mm Expanse, and the dreadful 4mm VITE that I haven’t yet thrown away. Not shown in the photo are a spare pen and a little Sharpie, both buried under the bag containing the diagonal. You can see that all of the eyepieces are still living in the boxes or cases they came in, and they’re held in place against rocking or tipping by a thick layer of bubble wrap taped into the lid of the tool box.

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Another sheet of bubble wrap sits below the top shelf and cushions the gear in the bottom of the toolbox.

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The bottom of the toolbox holds my ‘top shelf’ eyepieces and a lot of spare gear besides. The three Explore Scientific eyepieces came clamshelled in foam, and each one rests in the bottom half of its original clamshell. One of the top halves forms a bed for the 5mm Meade MWA. The two slots in the middle used to hold my Stratus eyepieces before I let them go – the ES models are smaller, easier to handle, and do a significantly better job. Now those slots hold the 32mm Astro-Tech Titan, my only 2″ eyepiece, the GoSky iPhone adapter I blogged about here, and a cord to hang my eyeglasses when I’m observing.

Around the edges I have all kinds of stuff crammed into the spare spaces. Clockwise from the top:

  • Contact info, just in case the case ever gets lost and found by someone decent. Has my name, address, email, and cell number.
  • Lens cloth, just in case.
  • Spare AAA batteries for the green laser, the red flashlight, and the laser collimator.
  • A ziploc. Never know when you’ll want a small waterproof bag. Sometimes holds spent batteries if I have to do a field swap.
  • Laser collimator. Reminds me, I need to blog sometime about how to collimate a laser collimator.
  • A set of hex wrenches for collimation.
  • Small pliers for the same purpose – I’ve swapped the hex bolts on a lot of scopes for standard hex-head bolts that I can tweak with pliers. Much better than farting around with hex wrenches.
  • Green laser. Super-useful when stargazing with newbies and old hands alike.
  • Tiny atlas – so I’m never without one. This is the Collins Gem Guide to Stars, which has little charts of the constellations and a short list of the most impressive DSOs for each one. Unlike Sky & Tel’s Pocket Sky Atlas, this thing truly is pocket-sized, and small enough to take up essentially no space or weight in the case. It has saved my butt a couple of times when I forgot all other atlases.

There is one other thing. In the third photo you can see a light blue bag through the intermediate layer of bubble wrap. I think that’s the bag the eyeglasses cord came in. Now I use it to hold a set of iPhone earbuds, which serve as a remote trigger when I’m taking pictures with the iPhone adapter, as shown and explained here.

That’s it – an inexpensive, sturdy, and above all roomy case for my eyepieces, with nooks and crannies for a whole lot more.

What’s in your eyepiece case?