Sunday, October 30, 2016
Issue #515: In the Dark with a 4-inch Refractor
In recent times, I've developed a new appreciation for what a small and inexpensive and simple telescope can do. That comes after spending plenty of years thinking you can't have fun without a big gun and a ton of electronics. One thing that's turned me aside from the big and complex is that after suffering last summer's back problems, I spent months where I didn't dare even haul a C8 into the backyard. That was coupled with my increasing turn to refractors, and, over the last couple of years, a desire to simplify, simplify, simplify.
During those past (almost) two years, I’ve come to want to not just reduce telescope headcount as described in the above piece, but to, yes, simplify as much as is practically possible the scopes I still own and use. While I will still haul quite a lot of astro-junk to a star party, it's not the ton of astro-junk of the last couple of decades, as you’ll find next week when you get a report on the 2016 DSSG. Honestly, I just don't have much patience for All That Stuff in this latter age.
There is a limit, though. While you can have tremendous fun with binoculars or a 60mm telescope once in a while, and while instruments in that class are all some of you ever use, I, like most of y’all, want to see a bit more than what the really humble instruments can deliver. I’ve long thought 4-inches of aperture is the practical lower limit for most of us most of the time. Even so, what the heck can you possibly see with, say, a fast 4-inch achromatic refractor on a cheap alt-azimuth mount? I found out at the Possum Swamp Astronomical Society’s (semi) dark site this past Saturday...
It looked like it was going to be a beautiful night, if a little cool as I judge such things lately, and I certainly wanted to get out there and observe. Frankly, however, the idea of loading up a tripod and a GEM mount and batteries and a big OTA and maybe a computer left me feeling slightly depressed. Still, I wanted to be at the site with my club buddies. So, what if...what if...I just packed the Explore Scientific AR102, a short 4-inch refractor, and my good old SkyWatcher AZ-4 alt-azimuth mount?
Sure, I probably wouldn't see much with that kind of rig—everybody knows you need at least 10-inches of aperture to see anything of the deep sky, right? —but I could bum looks through the scopes of my mates, and if I got tired of that I could just go home and watch TV.
One thing that encouraged me to head to the site even though I wasn’t in the mood for a pedal-to-the-metal observing run? I am now OK with going out there on iffy nights or nights when I might not want to spend more than two or three hours on the field (at most). Compared to the old days, when I lived at the legendary Chaos Manor South, the dark site is now just a hop, skip, and a jump away, a mere 30-minutes to the west.
Loading sure was sweet. 10-minutes—if that—to plop the 102 in the backseat and the AZ-4 in the cargo area of the 4-runner along with an eyepiece box. Out on the observing field setting up was similarly pleasant. No connecting anything, no alignments. The only concession I made to modern technology was that I brought along my Android tablet running SkySafari Pro for charts. I could actually have been just as happy with my current fave print star atlas, Sky & Telescope's Pocket Sky Atlas Jumbo Edition. It was all simple and easy, yeah, but I was still skeptical I'd see much with such a minimalist rig.
Once it (finally) got dark, it was time to see what this somewhat silly little scope could do, starting with globular star clusters. Surprise! M13 was beautiful and nicely resolved at high power. So was M2. So was M92. After those three showpieces, I did a quick tour of the Sagittarius and Ophiuchus (Messier) globs, nailing each and every one. Some were just fuzzballs, sure, but some would have remained fuzzballs even in an 8-inch, and all nevertheless looked good.
What really looked good Saturday night? The Lagoon and Trifid nebulae in one low power field using my el cheapo Zhumell 16mm 100-degree eyepiece, the Happy Hand Grenade. After that, I just spent some time cruising up and down the "teapot steam," the Sagittarius Milky Way, bouncing from one open cluster to the next. I didn’t obsess with ticking objects off a list, just relaxed and looked. I observed many other objects over the course of the relatively short night, but the trip was more than worth it just for the opportunity to drink in the wonders of Sagittarius in a wide-field telescope.
How about the dreaded chromatic aberration? I'll be the first to admit my eyes are not as blue sensitive as they once were, and for that reason the color purple was not very evident. Well, except on Venus. But who spends much time on Venus? Even Vega was not bad. Sure, there was come chromatic aberration haze around the star, but it wasn't like a kaleidoscope. On normal deep sky fields, you wouldn't have known the scope was a fast achromat. The stars were nice and tiny and sharp. I did have a look at Saturn, and the view, given the short focal length of the telescope and the resulting need to use a very short focal length eyepiece to get a good look at the planet, was rather impressive. Despite the low altitude of Saturn, Cassini's Division was nice and sharp.
I am currently focused on revisiting the Messiers, but did do a few NGCs too. The Helix Nebula, for example, which was quite impressive with a UHC filter. As far as the more challenging Ms (for a 4-inch), M72 was just a smudge, but there. M56 was not blindingly bright, but actually showed a little resolution.
No matter how nice a telescope is, it won't perform well without a decent mount. The AZ-4 is not a fancy custom alt-azimuth mounting like the excellent (and expensive) Half-Hitch mounts, for example. It's not finely machined, and there are no slow motion controls. There are adjustable tensioners/locks for both axes, a Vixen compatible saddle, an OK (extruded aluminum) tripod, and a nice big pan-handle. It's motions are smooth, very smooth, like the motions of a well-made Dobsonian, and I had no problem tracking objects at higher powers. When using a relatively short refractor, I do unscrew that big pan-handle, as it just gets in the way with anything shorter than, say, a 4-inch f/10.
While the SkyWatcher AZ-4 doesn't appear to be currently available in the U.S., you can get the exact same mount badged as the Orion Versago II for a somewhat higher price. The SkyWatcher mount was not only slightly less expensive than the Orion version, the AZ-4 came with a rather nice 80mm f/11 refractor. I have used this mounting with a C8 and it's usable with that much scope for casual viewing, at least. With the AR102, it's pretty perfect. Recommended.
And so it went for a few hours. Remarkably, I never tired of the 4-inch, and had no need to cadge looks through my fellow observers' telescopes. The only scope I used other than my own, really, was a friend’s StarBlast, which, being a 4-inch f/4, was more like my instrument than different, even though it was a Newtonian reflector. The ‘Blast delivered outstanding images, and it was clear there would be a tremendous amount of things to be seen with the little green guy. Seems to me that in addition to being increasingly enamored of easy to manage telescopes, I am also increasingly fond of wide-field views. Maybe that’s a consequence of having spent several years concentrating on very small slices of the sky when I was doing the Herschel Project.
Finally, the true beauty of astronomy with an ultra-portable 4-inch rig? Packing for the journey home. Again, 10-minutes, perhaps, and I was ready to roll, and a goodly part of that 10-minutes was consumed just by putting the caps back on my eyepieces. Driving off the field, I was honestly bowled over by the knowledge that not only could I see something with an ultra-simple, ultra-cheap telescope, but that I could see so much.
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I just had the same epiphany with easy to setup and light scope mount combo. My new job as a field application scientist means I travel overseas quite a bit, and most times I am too tired to lug my gear out to the dark sky sites...so for now its back to visual, and my most used visual scopes is either the 102 Celestron or my 130mm ST Orion OTA on a Vixen Porta Mount.
Rod,
Thanks for the surprise blog! I knew you'd be at the DSRSG so this was a nice surprise. I've been on a similar journey as you, with the recent purchase of a 100 mm SW Pro ED and an Explore Scientific Twilight II mount. I figure if 4" was enough for Scotty, well, it's enough for me. I'll still use my larger scopes, but I'll also take advantage of more opportunities with this smaller scope.
Clear skies,
John O'Hara
Thanks for the surprise blog! I knew you'd be at the DSRSG so this was a nice surprise. I've been on a similar journey as you, with the recent purchase of a 100 mm SW Pro ED and an Explore Scientific Twilight II mount. I figure if 4" was enough for Scotty, well, it's enough for me. I'll still use my larger scopes, but I'll also take advantage of more opportunities with this smaller scope.
Clear skies,
John O'Hara
# posted by 
: 5:25 PM
: 5:25 PM
My AR102, used on a ES Twilight 1 mount, is my grab 'n go scope for those nights when I don't want to haul out the 8-inch SCT, wait for the bigger scope to cool down, or stay out for hours. It is a great tool, and I've scored numerous galaxies with it well below mag 12.0--and had my best wide-field views of the North American and Rosette Nebulas (best with UHC filter). Plus, it's hard to beat the image quality of a refractor.
I don't know about the AZ4 mount, but I USED to have the Orion Versago II one. Our dogs were playing chase and knocked the mount over (it was folded up and leaning in a corner) onto a carpeted floor. And it broke! The Orion mount has a PLASTIC part that connects the METAL legs to the METAL head. The fall sheared a leg off at that point. Orion told me they could sell me a set of legs - I opted to buy a StarSeeker mount instead. Those folk that have the Versago II need to be careful!
Hi George...those parts are metal on my SkyWatcher branded mount, but it's five years old, now...maybe the mount has been cheapened up in recent times?
Interesting read Rod. My most used scope over the last few years for visual has been a 72mm frac on a mini-giro altaz mounted on a sturdy photo tripod. It gets me out there when normally I might not have the energy to haul the C8 out. Ok resolving power is limited, but there's plenty to see, seeing conditions don't affect it too much and a single zoom eyepice is all that's required. It allows me to get my 'fix' even if only for 30 mins. I have recently acquired a Tal 100mm F10 and I was interested to hear you can resolve plenty of globs with your 102, something the 72mm cannot do, so its obviously a big step up. I shall look forward to using the 100mm over the winter and seeing what she can do.
# posted by : 3:07 AM
: 3:07 AM
Hello Rod,
I am new to astronomy and decided on a nexstar 6se for a first telescope after some reading. I live close to you, in vancleave mississippi, a stones throw.
The one thing i hadn't read about was condensation/dew. Living in the deep south i guess i should have taken that into consideration, but new and all...All my nights so far have ended up in all completey soaked equipment withinn 2 hours.
I read up some the past few days on dew problems and just read an older article you wrote (2002) on combating this problem. Much insight, thnx!
Hopefully a dew buster and a heater for the main scope and eyepiece will correct that.
Living close to you i will have to go back through your articles for pitfalls for us in our locale. Again, Thnx Much!
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I am new to astronomy and decided on a nexstar 6se for a first telescope after some reading. I live close to you, in vancleave mississippi, a stones throw.
The one thing i hadn't read about was condensation/dew. Living in the deep south i guess i should have taken that into consideration, but new and all...All my nights so far have ended up in all completey soaked equipment withinn 2 hours.
I read up some the past few days on dew problems and just read an older article you wrote (2002) on combating this problem. Much insight, thnx!
Hopefully a dew buster and a heater for the main scope and eyepiece will correct that.
Living close to you i will have to go back through your articles for pitfalls for us in our locale. Again, Thnx Much!
# posted by : 9:50 AM
: 9:50 AM << Home
