CGEM DX 1100HD w/ Hyperstar?

[JGiambalvo]

I've been doing some research on a more serious rig to start imaging DSOs and have been leaning toward a CGEM DX 1100HD with Hyperstar. I was at first in favor of this option because of the seemingly simple learning curve and its forgivingness due to short exposure times @ f/2. I had been looking at a Starlight Xpress SX-814 Monochrome and some narrowband filters and I wasn't even going to bother with an auto guider. Am I being too optimistic with this setup? Any suggestions are appreciated.

[ollypenrice]

Personally I think the claim that the Hyperstar is an 'easy' imaging scope is utterly absurd. Yes, it is fast, so that makes for shorter exposures. Now consider some of the difficulties:

1 The steep light cone means that the focal depth is measured in microns so finding and maintaining critical focus is difficult, compounded by...

2 The rather primitive moving mirror focus system which was designed for the scope in focally tolerant F10 format. It was not designed for F2.

3 The shallow depth of field means that the slightest tilt in the chip will throw one side out of focus.

4 The collimation is highly critical at this F ratio.

5 The cable routing problem.

6 The asymmetrical diffraction artefacts arising from cameras which overlap the seocndary.

7 The impossibility of using a mono camera with filterwheel.

'Fast' and 'easy' simply do not go together in astrophotography, whatever the advertisers say. If you want 'easy' go for a small, fast apochromatic refractor.

Olly

[ollypenrice]

Sorry, to clarify my last sentence above, 'fast' as in fast astrograph is a lot faster than'fast' as in apo refractor. The fastest apos I know of are the Tak FSQs at F3.6 when reduced.

Olly

[knobby]

I've always looked at the Hyperstar and thought great idea but 'the camera is blocking some of the light path'

But Olly put it way better than me !

[ChrisLX200]

If they were such a great idea more people would be using it, the fact is that very few are.

ChrisH

[Tim99]

I have an ED80mm refractor and also an Edge HD 9.25 SCT.  Just getting started in AP but I have learned the lessons discribed above by Olly.  My ED80 with its wide FOV and excellent optics has already produced some wonderful DSO images for me.  When I tried to image DSO with the SCT, it was much more difficult to focus and my results were no where near as good.  This is coming from a beginner.  I have seen superb DSO images from guys who use the Edge SCT.  Some of them have even been taken at f10.  The trick I think is to find ways to solve the issues associated with that system.  I bought my SCT to use for Planetary observation and imaging and use the Refractor for the deep sky stuff.

Olly and others explained the basics to me when I was getting started in imaging:

For DSO you want a fast scope with a wide FOV (Field of View).  The Explore Scientific ED 80 Triplet Refractor was a perfect scope for me as a beginner and is relatively inexpensive.

For Planetary work, you want a scope like my SCT with a narrower FOV and good light gathering ability.  The planets appear very small in my Refractor but with the SCT, I am able to get the magnification required to make the planet large enough to actually see detail.

I think I said that right but the best advice I got was to understand the basic difference between imaging the planets and imaging DSO's.