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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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Howdy folks. I'm new, but I'm not new.  I have some equipment, but I haven't used it in a long long time, and I'm not that good.
Anyway, I was thinking about getting back in the game, but I'm not sure what equipment to use. Right now I have a SX H9 monochrome with 5 filters (RGBHaOIII), and my trusty NJP (it's the old kind before the GOTO).
What I was thinking was trying a big scope this time. Before I was using a 66mm f7 and a f8 6" newt, and the results were ok, but nothing to write home about.
I was thinking of getting a hyperstar 11". That would give me a focal length of 540mm, which is nice to practice with. Not to mention at F2, I'd be so oversampled that I could probably kick the tripod with no star trailing... My only real hesitation is the fact that you just don't see any good images on the internet with this scope. In fact, I havn't seen any good images with any hyperstar or faststar scope. Am I just having bad luck, or is there an inherent defect with this setup?
I know you guys are experts, so I'd like to hear what you have to say. I'll probably get a 800-1000mm APO as well. Using the CCD calculator, I can get most of the objects I want to shoot with these two scopes and my camera. And if I get a crazy hair and want to go close up on, say, M16, I can always use the SCT in SCT mode. One thing is for sure, the old NJP is solid as a rock.
Anyway, I'd appreciate your thoughs. Thanks!
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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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Oh yeah, more questions:
1. I've heard the rule that you can use the F-ratio to determine your sampling with your camera. In other words, with 9um pixels, and f9 scope is perfect sampling. With a faster scope I'd be over sampled, and slower, longer. Is this correct?
2. How do you determine your seeing? I here folks say that they have their sampling perfect, but their seeing only allows for X arc seconds, blah blah blah. What does this mean?
3. I'm in a city very close to the New York metro area. More specifically, I'm downt he street from David Letterman. The skies are not dark at all, but with the narrow band filters up to my eye, I can see all sorts of stars! I don't realy like the look of the Su OIII Ha photos, but perhaps there's another way to do RGB images with narrow band filters? Any filters in the Green band available?
Thanks again!
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ratdog11
member
Reged: 04/26/08
Posts: 81
Loc: surprise arizona
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I am very new to imaging so I'm no expert. I own a hyperstar 3.0 to use on my CPC1100. I agree that there aren't that many "great" images out there, but go the the starizona websight and go into hyperstarimaging than into the gallery section. You can view a wide variety of levels of experience and you can make a decision yourself. I've seen some outstanding images, but I've also seen the opposite. You judge for yourself.
One other thing to keep in mind, this is a great set-up if you are using such a slow scope and it's great if that's the equipment you will be imaging with. SCT's aren't the best for imaging but this is the best thing since sliced bread for this scope and F ratio.
Greg
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CPC1100
TV NP-127is
CGE mount
Orion 80mm shorty
Hyperstar 3.0
Canon 40D unmodded
QHY8
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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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Thanks Greg. I found that site, and yes, several folks have some really nice photos.
Since you have one, maybe you can answer a question. Is there room to stack filters? My RGB filters have a pretty wide band, so I'd probably have to stack an IDAS with the RGBs. 
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22479
Loc: NE Ohio
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Quote:
is there an inherent defect with this setup?
I don't know of any inherent defects, but there are quite a few compromises. A spherical primary only partially compensated by a misplaced corrector is probably the biggest, but there's also the large and asymmetrical obstruction caused by the camera (even if the camera is perfectly round there are cables in the way). Then there are whatever errors are contributed by the extra front end optics.
If you want to shoot at around 500mm why not stick with Tak and select instead an FSQ-106? There's certainly no shortage of exquisite images from those on the internet. It'd save some money and eliminate all compromise.
I've owned quite a few Fastar/Hyperstar compatible C8 and C11 telescopes, but I never considered trying to use them in that mode.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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Thanks John. The reason is mainly resolution. I'd like to have the option of shooting at 2600mm (or 1638 with the focal reducer) for deep shots. I've shot through an FSQ before, and it was indeed very nice, but as you know considering the time you've been on this forum (5 years! wow!), aperature is king with imaging. Considering the scale of the oversampling at f2, I can't see the central obstruction being that big of an issue unless your camera has very small pixels. Perhaps I'm wrong. 
What I still would like to understand is how to determine the maxium resolution you can shoot at given the atmospheric conditions. How do you look up, furrow your brow, and say, "Yep, about mag 3 today.."
Then once you know the condition of the sky, how to you apply that to scope choice with a given pixel size?
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PascalN
newbie
Reged: 04/13/08
Posts: 4
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See Greg Parker's website: http://www.newforestobservatory.com/
Greg's Hyperstar images are amazing. He has published a book of his HS images. The book is Star Vistas
http://www.newforestobservatory.com/index.php/books/starvistas/
I am about to get started with HS imaging on a C14. I am also in a light polluted area, and plan to try out an IDAS light pollution filter.
Cheers!
Pascal
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D_talley
professor emeritus
Reged: 07/07/05
Posts: 705
Loc: Richmond VA
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You asked about filters. I use the IDAS filter with my Hyperstar. I don't see any practical way to use RGB filters with the Hyperstar. You will need to remove the camera and the camera attachment then insert each filter.
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Dwight
TEC 140 APO
Meade LX200 14 OTA
Orion 12.5 DOB
Celestron C8+
Celestron 102AZ
Losmandy G11
Argo Navis
Canon 10d
Canon 350D
Hyperstar
ST-4 Guider
STV Guider
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22479
Loc: NE Ohio
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Quote:
Thanks John. The reason is mainly resolution. I'd like to have the option of shooting at 2600mm (or 1638 with the focal reducer) for deep shots.
Resolution matters; of course, but I don't think it supports the choice of an SCT. At the Hyperstar focal length of around 500mm a 4" telescope will deliver all the resolution one can use (camera resolution is only 3 arcseconds/pixel or so) without compromises and with the potential of a much larger FOV (image circle of the Hyperstar is limited). At the longer focal length all of the compromises of an SCT (field curvature, spherical aberration, coma) are brought to the foreground. At 2600mm or so, an 8" classical cassegrain can deliver all the resolution a camera can use (.7 arcseconds or so) - again, without compromises (except for the symmetrical obstruction) and, again, with a much larger image circle.
If you really want a single, dual purpose instrument the CN-212 seems to be a much stronger candidate than a C11/Hyperstar combo for only a little bit more money.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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Thanks guys. Awesome link Pascal.
John, great points. The reason I was thinking of using the C 11 was that I basically would have 4 scopes in one, F2, F3.3, F6.3, and F10 (though I'm not sure F10 is usable in my location due to poor seeing). But you are right. I'll definately check out the CN-212. Thanks!
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LightPolution
member
Reged: 08/15/08
Posts: 52
Loc: Greenwich, CT
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BTW, the other reason I was thinking of the hypestar is the fact that one 30 second exposure = over 5 minutes with a sky 90. I could fire off 240 exposures in 2 hours and have a very clean image, I'd think. Yes? No? Am I bonkers? 
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PascalN
newbie
Reged: 04/13/08
Posts: 4
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That's my thinking.
I also have a Sky90 with the f/4.5 reducer/corrector. But, for extended objects the "speed" of a f/2 system allows much shorter exposure times. The C14 with Hyperstar is F/1.9 !! With fl=710 mm. That gives the image scale that I'm looking for, with the promise of faster imaging.
Cheers!
Pascal
Edit: I have learned that a better estimate of the C14 Hyperstar f/1.9 focal length is 675 mm.
Edited by PascalN (08/17/08 12:33 PM)
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jay52
Carpal Tunnel
Reged: 09/26/04
Posts: 2280
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Quote:
That's my thinking.
I also have a Sky90 with the f/4.5 reducer/corrector. But, for extended objects the "speed" of a f/2 system allows much shorter exposure times. The C14 with Hyperstar is F/1.9 !! With fl=710 mm. That gives the image scale that I'm looking for, with the promise of faster imaging.
Cheers!
Pascal
Of course, 11" and 14" scopes accumulate a lot of light.
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jay
www.allaboutastro.com
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PascalN
newbie
Reged: 04/13/08
Posts: 4
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Jay,
Very true. And the C14 is a lot bigger and heavier than the Sky90 !! I've sure got to be hungry for photons to make this worthwhile.
Pascal
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