I am starting my RC8 imaging and start to see its power and resolution. It provides much more details than any of my previous refractors. I do have some problems with it. For collimation, I use the DSI method and it is very effective. The real problem is pinched 'triangle' stars (you can clearly see them when out of focus). Originally, I thought this was due to my reducer ccdt67. After I removed it, the pinched stars still showed up.
The problem showed up during the second day of imaging, not the first day. More specifically, I set up everything in my backyard and the first day imaging was fine, I got pretty round stars. Then I left the setup there for the whole day and started to image on the second day night. Then the pinched 'triangle' stars were all over the imaging chip. I wonder if the camera was too heavy to cause the problem, or the temperature was too cold to exert pressure or squeeze on the primary mirror.
The attached is my setup. RC8 with moonlite 2.5 and SBIG 8300 camera. My first image of this setup is Thor's Helmet. I have not done any post process with it. Just a HOO combination and it is really good. This image was done during the first day of the imaging so that there were no pinched stars. Thanks for any useful suggestions.