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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 700
Loc: Madison, WI / Gurnee, IL
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I keep making up my mind and then changing it over and over again, but as always, I find the opinions of CNers invaluable in stopping me from doing something I will later regret.
Mainly, I need a capable imaging system, for long/deep exposures. Of course, nothing can really beat the 24" and its solid mount (I am able to take 1200s unguided at f/13.2, I'm sure you'll agree that's pretty good)- but during the schoolyear I really don't have much telescope time there, and lately my public outreach hours are also on the fall, since elementary school teachers apparently see a need to use a 24" to show kids Jupiter rather than using an LX90. I still want to be able to do "real" science, which includes photometry and spectroscopy. My primary interests are emission/planetary nebulae, and planets themselves. Open clusters and irregular galaxies take second place.
So currently (equipment is all listed below), my main gun is a C11-CGE. The CGE is killing me: I expected a big EQ to be able to hold rock solid so long as it is well polar aligned. I guess all of the computerization tends to hamper my efforts. I do want a C14 in the future, if not for Christmas. It's a planet killer, and I don't think the C11 can match. But can the CGE keep up? (even if it means tweaking the mount).
I've also gone over the idea of an astrotech RC. As I figure, I think an ~f/6 11" SCT will beat out an f/8 8" RC for imaging, those are just the facts. I can always add the pretty spikes to my CAT. Refractor-wise, I think the 100ED is great, and I could only see replacing it with a 120ED or a 127 triplet later... but I think so long as I keep the C11 on hand, nothing will match in terms of planetary performance.
As far as imagers are concerned, I've just never liked CCDs. The DSLR feels more "natural" to me, and I'd like to keep it that way. Would it be wise then, to use the $1300 or so I have (that was going to go to an RC8) for a Hutech camera? That way I could do some H-a and IR studies.
I think until (if) I get a C14, the C11 should work just fine for me. If the C14 comes along, the RC8 makes more sense as it fills in the focal length gap, but if I can get a hold of a C14, I won't hesitate. Until now, that money will be spent on filters and possibly a modded DSLR.
Anything seem missing from this picture here? I know it's a bit scatterbrained, but I've been trying to convince myself over the last month or so of what I really want vs what I need vs what I can afford. I want to have equipment with which I can conduct research on my own, as my telescope time at Yerkes is nonexistent as of late.
Advice, comments, criticism, all welcome. Thanks in advance!
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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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Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 985
Loc: Oman
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Start by checking this, my latest DSO imaging set-up. I have just tried out the Canon 1.4xII and the Canon 2xII on the C14 Hyperstar. The 1.4xII works well, the 2xII introduces what looks to me like severe spherical aberrations to the extent that you cannot get satisfactory focus. You get squeezed between gullwings and tear-drops on off-axis stars. But on a C14 I feel that even the 1.4xII gives too much focal length most of the time. How often can one justify sampling at 1.0 arc-sec per pixel? You can actually observe the shimmering from the seeing even when you look at a star in LiveView. But on a C11 Hyperstar the 1.4xII may be worthwhile because you start off at coarser sampling. A C14 Hyperstar + 500D already samples at 1.4 arc-sec per pixel, an excellent match for average seeing conditions. I will post the test images in the next few days.
Other nice toys: a Baader Blazed Diffraction Grating coupled up to a Canon 100mm/2.8macro USM lens. Instant snapshooting spectroscopy on all the stars you can see with the unaided eye, full spectrum from 390nm to 1000nm in one go, at a dispersion of about 2.2 Angstroms per pixel. I have examples shot with a 20D here. The secret to better dispersion is the tiny pixels in the T1i. I have yet to attach the grating to the C14... But Baader also has what looks like a really cool compact spectroscope for use on an OTA yielding very good dispersion. Check out their website, much more sophisticated than the simple grating I own.
Of course, the next lot is a selection of all those Astronomik and Hutech filters that go inside the camera. I would suggest acquiring them in the following order:
UV/IR blocker for white light imaging
Astronomik Pro Planet 742 for IR imaging
Astronomik 6nm Ha CCD
Astronomik 12nm OIII CCD
Since you seem to be at a dark site in all likelihood the light pollution filters are of less interest. Also note that you need the "clip" filters in the "CCD" versions if your camera has clear glass over the sensor, otherwise they leak IR.
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Bored? Peruse my website:
http://www.samirkharusi.net/
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s58y
Postmaster
Reged: 12/12/04
Posts: 5503
Loc: Eastern NY
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For an 11-inch SCT, don't you need a pretty solid mount?
For example, I doubt my AP900 would be all that great for a huge 11-inch scope. I'd probably go for the AP1200, although they're not cheap, and are unpleasantly heavy to move around.
With my AP900, I doubt I'll ever go beyond an 8-inch or 9-inch scope, if I ever get a reflector at all.
I wonder if the "900" means it's OK for 9-inch scopes, and "1200" means it's OK for 12-inch scopes?
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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
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Mobius1
professor emeritus
Reged: 08/28/05
Posts: 700
Loc: Madison, WI / Gurnee, IL
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Samir, looks like a great setup! I actually just bought that remote for myself and it is a lifesaver. I'm on my way to purchasing a grating in the next week or so (either the rainbow optics or shelyak staranalyser, the baader is nowhere to be found). A CLS-CCD clip is also on the list, as I do travel to dark sites, but during the school year I'm in mag 3-4 skies... occasionally 5-5.5 if the neighbors and city are considerate, usually early mornings in the winter.
As far as planets go, I'm looking into IR and UV filters, as well as an RGB set, but currently my planetary imager is a Meade DSI. I wanted to go Lumenera, but I can't use that for guiding via PHD. I don't know if the hyperstar is happening yet or not, as if I will be getting a C14, there's no sense in getting a C11 hyperstar.
Seems that a T1i might be a good buy, though. I'd want the filter removed (the astronomiks I have are all CCD versions) so that I can play around with IR imaging. It's always easy to add a blocking filter.
Regarding the mount, that's what I'm afraid of. Celestron does sell a CGE 1400 kit, so the mount should handle the OTA just fine, but I'm not so sure about imaging. Seems that the G11 might have been a better choice, from what I hear it has superior gearing. The AP mounts are way out of price range... they cost more than a CGE-14 to begin with.
Samir, you have the CGE/C14. How does it fare at f/10 and f/6.3 for imaging? I'm assuming an autoguider and balancing are critical.
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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 (10/22/09 12:28 AM)
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Samir Kharusi
scholastic sledgehammer
Reged: 06/14/05
Posts: 985
Loc: Oman
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Just drop a line to Thomas Baader at the Baader Planetarium website (contact@...) and he will give you up to date info. The grating cost me around $250 including various adapters to connect it to eyepieces and to an OTA. The instruction manual is here. The much more elaborate Dados Spectroscope is described here. Thomas Baader, if I recall correctly, mentioned that it costs around 1200 Euros. Anyway that was too high for my just suck-it-and-see interest.
The CGE, IMHO, is somewhat better than the G11, and often cheaper, especially in kit form with a C14 or C11. The only mount "upgrade" I would recommend is to an AP1200 type mount at a much higher price; perhaps $12,000 by the time you have added necessary accessories. The CGE should work well for DSO imaging with a C14 Hyperstar. It's not really heavy enough for f7 or f11 DSO imaging, except with Adaptive Optics and a suitable dual-chip astro CCD. But note that with tiny pixels (eg in the Canon 500D) the image scale is already seeing-limited at f1.9! With the Canon 1.4x tele-extender you get to 1.0 arc-sec per pixel, overkill at most locations. So going to f7 or f11 for loooong exposures will normally be empty magnification. OK for subs a few seconds long but not really several minutes long, as is required for skyfog-statistics-limited regime. The CGE is also satisfactory for planetary webcamming at f25 to f30 with a C14. Not as robust as an AP1200, but quite satisfactory. The LiveView mode of current Canon DSLRs can be accessed by ImagesPlus and from Mike Unsold's examples, looks like an excellent substitute for the better webcams. The top webcams like the Lumineras are mono, with all the hassle of filter wheels, consequently of no interest to me. I can't stand filter wheels even for DSOs, never mind chasing things to freeze Jupiter's rotation. In brief, if you are purchasing both an OTA and a mount, then the current sensible choice would be the CGE Pro + The C14 Edge HD with a Hyperstar. Two TV eyepieces for visual, a 2.5x or 3x Barlow and you should be fully in business for both DSOs and planetary using a LiveView DSLR. These toys do suck us in, slowly but surely.
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Bored? Peruse my website:
http://www.samirkharusi.net/
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