If your anything like me, and it looks like you will be. Imaging is going to be a slippery slope. You will start with 30 second subs (this was me in August last year) but soon you will push for more, you will move up to guiding. Getting more nebulosity from longer subs you will find that your DSLR is too noisy and you will want a cooled camera.
You mentioned an OAG, this is the stage I am at now. To get an OAG to work on a newt you need the room to put it. To do this I moved the mirror up the tube. This creates more problems F4 is a steeper light cone than F5, If more of the light cone is in the focuser (more backfocus) then not only does the focuser need to have a large internal diameter, but the secondary mirror needs to be bigger.
My newt came stock with a 2 inch 10-1 focuser which has been replaced with a 2.5 inch moonlite motorised one. The secondary was the 70mm "oversized" imaging one, which has now been replaced with an 88mm mirror.
Collimation for imaging is nothing like collimation for viewing, A laser and a cheshire do the same thing eliminate PAE. To properly collimate the scope you need to eliminate FAE aswell, and this is where an autocollimator comes into play.
Quote:
Originally Posted by alistairsam
the cats eye collimation tools are very accurate, if not a cheshire and laser might do.
|
All in all I would probally have got the F5 if i had my time again, I dont think the trouble of a cheap F4 is worth the payoffs. If I had an endless bank account I would buy an Orion optics AG 8-16. Cheap scopes skimp on all of the bits you need to be precise to get F4 to work well.
My 2 cents.