pixshifter
member
Reged: 10/04/09
Posts: 16
Loc: Santa Clarita, CA
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After being talked down from a large aperture scope by the helpful folks here at CN (see this thread: Newtonian or SCT? ) I've decided that my first telescope will be a small refractor. Keep in mind my primary goal is astrophotography. But it will also be used as an auto-guiding scope down the road when I get an 1100 HD. The consensus seems to be 80mm. I'm assuming I should be looking at apochromatic triplets? I have these candidates on my list:
Astro-Tech AT80EDTA f/7 ED triplet apochromatic fl=560mm $700
Vixen ED80sf f/7.5 ED apo fl=600mm (a doublet??) $550
Meade 80mm Series 5000 ED APO triplet f/6 fl=480mm $800
Explore Scientific 80mm f/6 ED APO triplet fl=480mm with finderscope $800
This will be my first and only scope for a while. So what do you think of these choices? Any other comparable suggestions? I will be putting most of my money into the mount to start with. Probably a CGE or a G11. Will I be able to mount these scopes to these mounts?
Any help would be appreciated.
Jay
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Jay
Vixen ED80sf
Celestron CG-5
Canon T1i
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jmX
super member
Reged: 04/23/09
Posts: 180
Loc: Orange County, CA
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Skywatcher Equinox 80 + Televue 0.8x Flattener
OR
Orion Eon 80 + Televue 0.8x Flattener
Same scope either way, and its a perfect combo. I get perfectly round stars all the way to the edge of my Canon DSLR Crop sensor with that.
With the reducer it works out to 400mm @ f/5. Fast. Flat. Cheap. Great quality results.
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Jon
C6N + CG5
Skywatcher Equinox 80 + CGEM
http://jmx.ls1howto.com
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jmasin
scholastic sledgehammer
Reged: 12/22/08
Posts: 833
Loc: Murphy, TX (DFW)
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Don't rule out the Orion EON 80 ($699) I've heard great things about that scope. It is on my short list for larger objects/widefield or when I don't feel like lugging out the 8".
Just a thought.
PS. Good choice by the way  There's nothing more rewarding than getting a good start and building momentum!
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Cheers,
Jon
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Orion Atlas 8" (203mm f/4.9 on Atlas EQ-G)
Tasco 60mm (~35 years old and still kicking!)
Nikon D300, 80, 70 & many lenses
http://www.pbase.com/jmasin/astro
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Taylor
professor emeritus
Reged: 07/10/05
Posts: 601
Loc: Federal Way, WA
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My vote goes for the Vixen ED80sf.
I have one and it is an excellent refractor. I had an Orion ED80 a couple years ago, and they both had excellent optics.
I replaced the focuser on my ED80sf with a dual speed unit which is a major plus when using my CCD imager.
The ED80 is an ED doublet using FPL-53.
Here is a decent deal on it from Woodland Hills - http://telescopes.net/doc/2500/mftr/Vixen/item/5861
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Televue TV-85 and Panoramic mount
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DaemonGPF
Post Laureate
Reged: 03/22/08
Posts: 4035
Loc: New Mexico
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Astrotech OTAs are superb quality. My next scope is either an AT80 or an AT-RC8. The build and finish is excellent, focusers are smooth, and they show no signs of CA that I could detect even at higher powers.
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-Josh
http://cleardarksky.com/c/AlbuqNMkey.html
My AP Gallery
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s58y
Postmaster
Reged: 12/12/04
Posts: 5629
Loc: Eastern NY
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I'm not familiar with these specific scopes, but things to look for:
1) Good focuser that won't sag, slip, etc. -- 2-inch Feather Touch, for example
2) Good (matching) field flattener that covers whatever imaging chip you're going to use.
3) Good color correction -- probably not a big problem with 80mm APO triplets.
I used to image with an 80mm scope plus a guidescope on a G-11. The G-11 has plenty of capacity for this, and you should be able to get good tracking, especially once you start autoguiding. Unfortunately, back when I got my G-11, they had problems with the so-called "76 second" error, but autoguiding was able to track well enough for the small 80mm scope. I don't think G-11s have this problem anymore.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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revans
Carpal Tunnel
Reged: 09/26/05
Posts: 1536
Loc: Fitchburg, MA
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You don't need an apo or even an ED for deep sky astrophotography. A regular achro is just fine as long as you handle the violet halo's in post-processing (which is simple with Noel Carboni's Astronomy actions for Photoshop... assuming you have Photoshop) or use a minus violet filter. If you go with an achro, you can afford more aperture for the same focal length. I really like the Orion 120mm F5 achro which sells for only $320. If it were me, I'd put most of my money on a real good tracking mount than on a first scope... you will always have the mount but you will eventually put many scopes on it over the years. There's nothing worse than an expensive scope on a cheap mount 
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Rick Evans
http://www.freewebs.com/revans_01420/
"The universe is there for us to see, but it cannot be understood without learning its language -- mathematics." Galileo Galilei
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 745
Loc: Madison, WI / Gurnee, IL
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On that note, I have an Orion 120mm f/5 and minus-V filter I would gladly sell to you... BUT those violet halos are annoying, and the M-V filter gives you a yellow hue to the final image. I switched to the APO because of those factors, the UV saturation on those stars was insane on long exposures, I'll see if I can dig up some examples.
I do like Orion products (they have the ED, EON, and a set of f/7 102mm and 110mm refractors, but I'm not sure those are true APOs- maybe someone will chime in). I also really like anything Astro-Tech or William Optics. I have WO 66SD: same as the AT, really, which I liked a bit more but I got a better deal on the WO.
I also owned a WO ZenithStar 80mm FD (fluorite), which had superb color correction. I only moved up to the 100ED, because while an f/9, I figured that the 100 was a better all around scope (I could bump up the magnification more than the 80mm), and the 80mm was too big for a guidescope. I'm actually hoping to move up to a 120-130mm APO, but I have to wait until a good deal comes around... the aperture fever will get to you quick, especially when you realize how sharp the images are.
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Martin
William Optics 66SD
Orion 100ED
Orion 120-ST EQ
PST-Ha
Celestron CGE 1100
Canon Rebel XSI with Astronomik filters
DSI-IIC
Homemade spectroscope in progress...
Yerkes Observatory Volunteer
(24" Cass on weekends)
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 745
Loc: Madison, WI / Gurnee, IL
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Here goes, some examples of what the 120mm f/5 can and can't do. This was a Canon 350D, 30sec subs, ISO1600, on an Orion EQ-3 mount. M42, looks great but the CA is crazy...
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Martin
William Optics 66SD
Orion 100ED
Orion 120-ST EQ
PST-Ha
Celestron CGE 1100
Canon Rebel XSI with Astronomik filters
DSI-IIC
Homemade spectroscope in progress...
Yerkes Observatory Volunteer
(24" Cass on weekends)
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 745
Loc: Madison, WI / Gurnee, IL
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Same technique applied to Markarian's chain in Virgo. You can see that the scope has quite a bit of resolving power (I was able to identify 21 galaxies in this image), but any bright stars still are oversaturated. I did use the minus-V filter a bit, but I just didn't like it enough to continue using it- others' opinions might vary.
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Martin
William Optics 66SD
Orion 100ED
Orion 120-ST EQ
PST-Ha
Celestron CGE 1100
Canon Rebel XSI with Astronomik filters
DSI-IIC
Homemade spectroscope in progress...
Yerkes Observatory Volunteer
(24" Cass on weekends)
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 745
Loc: Madison, WI / Gurnee, IL
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Just for comparison, here's M42 also using 30sec ISO 1600 subs (Canon 450D this time, and a CGE), but with the 100ED. Couldn't find a pic through the 80mmFD on my facebook page to download, but image quality was similar. A bit wider FOV, lower magnification, and slightly better color correction on the 80mmFD.
PS. Don't look too much into the darkness of the background sky or anything when comparing these pics. The M42/120mm was taken at the Yerkes Observatory grounds, and has 128 frames stacked, while the M42/100ED is taken from my backyard and is 16 frames.
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Martin
William Optics 66SD
Orion 100ED
Orion 120-ST EQ
PST-Ha
Celestron CGE 1100
Canon Rebel XSI with Astronomik filters
DSI-IIC
Homemade spectroscope in progress...
Yerkes Observatory Volunteer
(24" Cass on weekends)
Edited by Mobius1 (10/19/09 08:56 PM)
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 745
Loc: Madison, WI / Gurnee, IL
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Sorry for flooding this thread with images, but one more. Here's M13 with the Zenithstar 80FD, 32 x30sec, 350D, ISO1600. Don't remember where it was taken, but at a dark site, either Yerkes or south of Phoenix, AZ.
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Martin
William Optics 66SD
Orion 100ED
Orion 120-ST EQ
PST-Ha
Celestron CGE 1100
Canon Rebel XSI with Astronomik filters
DSI-IIC
Homemade spectroscope in progress...
Yerkes Observatory Volunteer
(24" Cass on weekends)
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jmX
super member
Reged: 04/23/09
Posts: 180
Loc: Orange County, CA
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Mobius, WOW, that m42 starfield is horrible! I'm new to refractors and I knew there'd be some CA, but I had no idea it could be that bad. Thanks for posting that.
Pixshifter, you can go here to see my M42 taken with the "Orion Eon 80" aka "Skywatcher Equinox 80" to compare and see how the purple halos are basically non-existant. That may be something that is a priority for you.
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3397451/page/0/view/collapsed/sb/5/o/all/fpart/1
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Jon
C6N + CG5
Skywatcher Equinox 80 + CGEM
http://jmx.ls1howto.com
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pixshifter
member
Reged: 10/04/09
Posts: 16
Loc: Santa Clarita, CA
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Martin,
Thanks for the pics. Wow, the violet halos are pretty bad in that first pic. Based on that, I think I'll spend the extra money on an APO.
What makes you say that an 80mm is too big for a guidescope? Should I be looking at a 66 instead? From the size of m42 in your pics, it makes me think that maybe I should be looking at the 100ED! I'm confused.
Also, isn't the Orion EON/Skywatcher Equinox a doublet? Or should I even worry about doublet versus triplet?
I was leaning toward the ES 80 because it seems complete for the money. It comes with a finderscope with illuminated reticle, a 2" diagonal, an eyepiece, a two-speed focuser, a saddle plate and a case. But there doesn't seem to be any feedback on the ES, so it is a bit of an unknown as far as optical and mechanical quality. Although I think I read somewhere that the Meade and the ES are the same scope.
Jay
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Jay
Vixen ED80sf
Celestron CG-5
Canon T1i
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jmX
super member
Reged: 04/23/09
Posts: 180
Loc: Orange County, CA
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Quote:
Also, isn't the Orion EON/Skywatcher Equinox a doublet? Or should I even worry about doublet versus triplet?
Jay
If you are somehow unhappy with the results you see on this board from the Equinox 80, then I suppose you could start worrying about doublet, triplet....but my feelings are the results speak for themselves. When I was deciding what to buy, I looked at astrophotographs for days, noting what hardware was used as well as which corrector lens....finding a perfect pair is very important.
I suggest you do the same...look for the results you want, and then copy that setup.
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Jon
C6N + CG5
Skywatcher Equinox 80 + CGEM
http://jmx.ls1howto.com
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revans
Carpal Tunnel
Reged: 09/26/05
Posts: 1536
Loc: Fitchburg, MA
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Have you tried to remove the halo's in post processing using Noel Carboni's actions for Photoshop... they are no longer a factor for me after two iterations... I really do believe that a simple achro is fine for deep sky... especially for a beginner... I loved the Orion 120 F5 so much that I bought two of them, but later gave one to a friend who gave it to an astronomy club in Egypt. Hopefully it is living a useful and appreciated existance there...
Anyway... attached is an M31 I took a few days ago with the Orion 120mm F5... no violet halos are there??? It is a short exposure... only half an hour under a full moon and in full city lights.... but this scope does better than my SCT which is free of chromatic aberration (but shows field curvature)...
So my recommendation stands, at least in my opinion...
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Rick Evans
http://www.freewebs.com/revans_01420/
"The universe is there for us to see, but it cannot be understood without learning its language -- mathematics." Galileo Galilei
Edited by revans (10/19/09 10:38 PM)
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pixshifter
member
Reged: 10/04/09
Posts: 16
Loc: Santa Clarita, CA
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jmX,
Thanks for posting that link to your pic. Great shot! The results do speak for themselves! That's one of the best M42s I've seen!
And good point about copying a known good setup.
Jay
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Jay
Vixen ED80sf
Celestron CG-5
Canon T1i
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revans
Carpal Tunnel
Reged: 09/26/05
Posts: 1536
Loc: Fitchburg, MA
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This is just an excellent example of inadequate post-processing of a series of subs from an achro... at least in my opinion... it is certainly possible to 1) completely eliminate the violet halos and 2) to reduce the overexposure of the nebular core with proper post-processing.
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Rick Evans
http://www.freewebs.com/revans_01420/
"The universe is there for us to see, but it cannot be understood without learning its language -- mathematics." Galileo Galilei
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s58y
Postmaster
Reged: 12/12/04
Posts: 5629
Loc: Eastern NY
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Quote:
Wow, the violet halos are pretty bad in that first pic. Based on that, I think I'll spend the extra money on an APO.
Sounds like a good plan. The most common advice you hear is to start out imaging with a small APO refractor. It's better to collect good data (without halos, for example) rather than trying to process out problems afterwards.
I started out with a very old telephoto camera lens that had bad blue/violet halos, and was glad when I switched to an 80mm APO triplet -- no more halos, but there were field curvature problems, even with a flattener. Now I'm looking for some sort of flat-field Petzval scope, like the NP101, so I can move up to a full-frame DSLR.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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revans
Carpal Tunnel
Reged: 09/26/05
Posts: 1536
Loc: Fitchburg, MA
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I can't do anything about your very overexposed core of M42 because I don't have your shortest sub to work with...(if I did, I could definitely solve that problem) but here is a post-processing that at least diminishes the negative aspects of achro scopes. Your image was low res and I'm sure that if I had access to your complete dataset the result would be virtually indistinguishable from an ED scope image 
I don't think it is so necessary to buy glass that is free of chromatic aberration as long as it is relatively free of spherical aberration, coma and astigmatism. Chromatic aberration is the least of all worries and is easily processed out of a deep sky image (more difficult on planets though). I'd still put most of my cash on a decent mount, not one of these mediocre ones that we see so much of for a few hundred dollars... I'd rather have a larger aperture achro scope that can gather enough photons than a small aperture ED scope or apo scope that struggles to bring in enough light for a decent deep sky image. That's why I like the cheap Orion 120 mm F5 achro.
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Rick Evans
http://www.freewebs.com/revans_01420/
"The universe is there for us to see, but it cannot be understood without learning its language -- mathematics." Galileo Galilei
Edited by revans (10/20/09 12:26 AM)
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