Quote:
Originally Posted by alpal
I just checked out the TS UNC 10" f/4 Newtonian.
using Dave Keller's Newt for windows 3.1.
(Luckily I have a Win XP laptop to use the program because it won't run on a modern 64 bit operating system.)
I found that even that needs a larger focuser than a 2'"
There was 75% vignetting of the rays at the front aperture & the focuser.
I also notice that other 10" f4 systems use a 3" or larger focuser.
My 2" RCC1 coma corrector goes deep inside the focuser so even that would cause vignetting.
I need to use that RCC1 so that I can use my QHY9 + filter wheel + OAG = 70mm of back focus.
What is going on?
cheers
Allan
|
Dont worry so much about the 75% rays, what you want to do is get the 100% rays covering your chip. Also you need to set your focuser camera travel to the backfocus of the camera outside of the focuser. Here is a 12 inch f3 design from newt for the web (which means you dont need to use the software you can just run the webpage version) using 55mm camera backfocus you will need a 3 inch focuser and a 120mm secondary.
Why not look at reducing a more modest scope with the ASA reducer corrector?
Here is the website btw
http://stellafane.org/tm/newt-web/newt-web.html