Beginner DSO imaging question

[AlistairHowie]

Firstly, I will say from the outset that I fully realise my CPC1100 is completely inappropriate for DSO imaging - 2.8m focal length, inadequate mount, poor tracking, and not at all easily mounted on a wedge. And ignoring the Hyperstar option for a moment ....

Is there some reasonable unguided DSO imaging that I could try with the Meade 3.3 focal reducer, keeping subs to 30 seconds or less and using a decent CCD? I know "every photon counts" and 30 seconds is very short, but is is possible to strack them up to a reasonable image? Would the answer be different with a more expensive CCD with less noise and greater sensitivity? If so, how much more expensive??

I suspect the answer is no .... but just wanting to double check.

Many thanks

[jgs001]

Alistair, You're right, it's not ideal, but I'd suggest trying it and see, you may find the results surprise you.... I started out imaging with an ST80 on a NexStar SLT (super lightweight AltAz) and an unmodded SLR. With enough subs (of 30 to 45 seconds), I was able to pull the bubble nebula out.

[Tinker1947]

I think your right the answer is properly "No" Horses for Courses as they say, you better sign up for overtime for the replacement gear...i think 30 seconds will leave star trails, you might have to go as low as 5 seconds and that won't collect many photons.

[dph1nm]

Use a CCD with large pixels, or one that can be binned up in hardware to create larger pixels. This reduces your effective focal length the something more manageable. A lot of people seem to forget that what really matters for tracking is not the focal length of the scope but the final pixel scale on the chip. Anything above 1" per pixel and I reckon you have chance in 30sec - and 30sec is more than adequate for DSO imaging, especially with a decently sensitive CCD. You just need the computing power to save and stack a lot of images!

NigelM

[AlistairHowie]

Computing power won't be an issue. Can anyone suggest a respectable CCD that will work with a reducer, either 6.3 or 3.3? Are there any specific issues with a 3.3 reducer, or is just more of the same compared to the 6.3, if you know what I mean?

[ollypenrice]

The issue with the 3.3 reducer is that it is a primitive thing dating back to the early days of CCD when chips were tiny. It will only give an acceptable field on a very small chip. It is high time that all, and not just some, of the vendors issued this health warning. I gave one away. The second hand value should be approximately that!

I woudn't be inclined to spend serious money on a setup that will never really work well. For a budget dabble at F3.3 you could try a small chip camera like an Atik 16ic. They come up quite cheaply.

I don't entirely take NigelM's point, above, that increasing your pixel size reduces your effective focal length. In one sense it does but in another it doesn't; it won't increase your field of view. With your focal length and the restricions of the 3.3 reducer that is quite an issue.

If you change your scope you are in danger of craving the exact opposite of the camera you have selected for the 11 inch SCT...

Olly

[AlistairHowie]

Thanks, Olly.

I'll stick with visual and just look at your pics.