I use a Coma Corrector on my 8" f/4 scope purely for imaging though. On my 8" f/6 scope I don't feel it needs it, I haven't noticed any coma at the edges, although I do only have a couple of EP's to choose from.
EDIT: BTW what scope are you using to make you think you need one? I think any Newtonian below f/5 should really use one as the lower the focal ratio the more coma you will get.
I have skywatcher 150/750 f/5 and I found the edge of the pics the stars look like a comet ..then one day I've read another article for other stuff they talked about coma corrector thats why I have such thought....
reflector
Last edited by malau; 11-03-2014 at 10:10 AM.
Reason: forgot to mention reflector...
I use a Rowe corrector made by Baader in my 10" f4.5 for imaging. It needed some fiddling to get the spacing right between the sensor and the corrector, but worth it, IMO.
Visually it doesn't bother me, but it's a personal preference.
Cheers,
Andrew.
I use a Baader MPCC mk3 with my 8" Newt at F4. Here are two comparison photos, both single frames, first without, then with a coma corrector. Its not perfect( probably due setup ) but its much improved. Focus on the first shot was a bit out also.
I use a Baader MPCC mk3 with my 8" Newt at F4. Here are two comparison photos, both single frames, first without, then with a coma corrector. Its not perfect( probably due setup ) but its much improved. Focus on the first shot was a bit out also.
I have a problem with my focal reducer/field flattener (coma corrector) It's great as a focal reducer 10/6.3.
But I have an ACF meade OTA so it flattens an already flat field - resulting in stars becoming oval in the tangential aspect.
Here's an example of ETA (3 mins ISO800)