Image of the day

From the
ATWB Customer Gallery

Milky Way with ISS

My Account

New to Astromart?

Register an account...

Need Help?

reflector vs. refractor

Started by rchozick, 09/08/2004 11:00PM
Posted 09/08/2004 11:00PM Opening Post
I am new to reflectors. I have been using an 8" SCT and a 4" APO refractor. I think my Orion is pretty well collimated and I find that it is great for dark fuzzies but on double stars it is only so-so. I have not used it much or at a dark sky site but it seems it doesn't have the detail but a lot of brightness. I know I would see more from an f/6 10" of better quality. Is this what I should expect on an Orion f/4.8 reflector or is my collimation bad or optics bad? Maybe I am expecting APO refractor performance on something that is not meant for it. I am glad to use my APO on details and reflector on dark fuzzies but I just wanted to make sure this is normal.
Posted 09/09/2004 07:39AM #1

You say you have an 8" SCT? Do you mean 8" Dob? Anyway, short focal-length reflectors will almost always perform as you describe. There's not only the coma introduced by the short FL, but also the large (percentage-wise) secondary obstruction. I used to have a Discovery 10" f/6 (I now have a Starbuckets 12.5 f/5). The f/6 makes a HUGE difference for all kinds of reasons - probably the Disco mirror was better than average, too. My current 'scope has a Royce mirror and high-end secondary, so the f/5 doesn't seem to be a problem. You ask about collimation as well - this is absolutely critical when using any system as fast as yours.

Posted 09/09/2004 07:53AM #2
I should explain better. I have been using the 8" SCT and 4"APO up until now. I just got the 10" Orion reflector. I am trying to see if the 10" reflector is better for dark fuzzies than the 8" SCT. It seems the image is not quite as sharp but contrast and brightness are greatly improved. I am already seeing that I need a good quality 10" f/6 but I wanted to spend some time with a reflector at a low cost.