GSO RC 8" and DSLR question

[Nico13]

Hi all,
Thinking about the above mentioned scope as an upgrade from my current SCT for use with my DSLR APSC size sensor and was just wondering if anyone was using a similar setup and if it suffered with any vignetting issues? :question:

Thanks for any help in this area.

[rmuhlack]

Can't speak to the RC8, but I can tell you that there is little vignetting when using a APS size chip on a Vixen VC200L, even with the 0.71x reducer. A flat (unstretched) from last night is attached. The VC200L includes a triplet flat field corrector as standard, so even without the reducer the field is fully corrected out to a 44mm image circle (ie a "full frame" DSLR).

A VC200L is a lot more expensive than a RC8 though so that is obviously a consideration. The focuser is from all accounts a zillion times better than the GSO though (not hard to believe if my GSO newts are anything to go by), so no need to upgrade there.

[Nico13]

Thanks Richard,
That's not too bad at all, wouldn't take much to flatten that out.
The VC200L was definitely another scope of interest but yes the price is also a consideration so still looking at this stage.
Oh by the way just loved the deep M104 post you put up, nice work.

[Paul Haese]

NO problem whatsoever Ken. I used a D40 with my RC8 for over a year. Below are a few of the images I did with that setup. All taken from 2008 to 2009. No vignetting present in those images. Some vignetting in the subs but using flats got rid of those problems.

http://paulhaese.net/trifidcloseup.html

http://paulhaese.net/NGC5128closeup.html

http://paulhaese.net/NGC4945.html

[Nico13]

Thanks Paul,
I noticed on the image links that you had been using a Tak flattener, I was under a miss comprehension that the the RC 8" was a flat field scope and not requiring a flattener.
Nice shots by the way as that's what I'm hopping to achieve with an upgrade.
How flat are the the images without the flattener?

[Paul Haese]

Hi Ken,

RC scopes are not flat fielded in their native form. They do however correct for coma. The field on an RC8 has a bit of field curvature and you could get away without having a flattener if you crop the image. This might limit the targets you image though.