I have just aquired a 10" RCOS f9 tube and was wondering if there are any 3rd party field correctors I could use on it.
RCOS dont make this scope any more but do make a 10" f7 Astrograph and have a dedicated Field corrector for it but they said it NG for mine. They never made one for mine but suggest using one from a 12.5" RCOS and averaging the focus between the centre and edge. I am not too keen on this and so looking for an aftermarket item that may/will suit.
I want to aquire ccd images with this scope using large format chips such as ST11000 and DSLR cameras so thought it may be appropriate to discuss it here.
regards
Nick

Hi Nick,

Generally, a FF custom designed for a specific telescope will work best. If that's not available, the next best thing is to find a FF that is designed for the same type of optic as your telescope (R-C) and as close as possible to the the same focal length. If same focal length is not available, a FF designed for a slightly longer FL will work better, as it will just undercorrect the image, while a FF desgined for a shorter focal length will overcorrect.

I would suspect that a FF for a 12.5" F/9 RC will also not be a very good fit for your scope. It will undercorrect your field of view, which is an improvement compared to overcorrecting, but is still not ideal. If such a thing exists, a FF for a 12.5" F/7 RC would work much better for your scope than the other two.

Regards,

-Paul

Hi Paul,
thanks for your input and information. I have not been able to find a FF for my scope but now that I am armed with some more information, I have a bit more to go on. I think I understand what you are saying about the FF for the 12.5" RC undercorrecting the field curvature, so not all of the curvature is taken out. Do you know of any 3rd party FF that may suit?
cheers
Nick

quote:

Originally posted by Nickb00:
Do you know of any 3rd party FF that may suit?

Sorry, Nick, I don't. Maybe someone else here knows..

I don't know if Philipp still does custom work, but you may want to contact Philipp Keller from Astro-Optik to see if he can build one for you or maybe he knows if one already exists. Another one to check with is Mark Rieck from Teton telescopes -- he offers a few different RC's and may have contacts to find you a proper field flattener.

Regards,

-Paul

Hi Paul,
Thanks for the lead! I will definately chase them up soon. I have only seen first light once with my new scope (visually) and it was quite impressive. I am waiting for my AP1200 to arrive (next few weeks) and it can then be properly set up in my observatory. About 6 months ago I sold nearly all my gear to get the RC10 and AP1200 to get into some seriously fun astrophotography. It may take a few months before I know the real extents of field curvature in my scope (ccdinspector to the rescue) and then I will begin the quest for the holy FF.
Clear skies and thanks
regards
Nick

I have a 10" RCA. The last one they made.

Star Optics might make a reducer for you. They make RC Optics optics.

Hi John,
Yes I had thought of contacting Star Optics but have only contacted RCOS at this stage who said they dont make them for my scope and to try one for a 12.5" scope. Maybe a direct email to Star optics is the go and as you say, hopefully they could make one for me. Oh boy, another lead!
thanks
Nick