I have been doing visual astronomy since the 80s, but I just started doing astrophotography last year. I started by buying a QHY5II715C for planetary photography with my 8se and my results were good, but I missed the memo on using an IR/UV cut filter so I expect to get even more detail on Jupter in the coming months now that I have a cut filter.
My wife got me a SeeStar S50 for Christmas (she’s the best!) so I have been shooting deep sky objects with it, and I have been amazed at how well stacking short exposures worked. I saw that Quiv and others on YouTube had used my same QHY5II715C for deep sky astrophotography with the short exposure technique. I thought I would give it a try. My first choices for objects were the ones that were too small in my SeeStar photographs - the Ring Nebula, the Dumbbell Nebula, and the Crab Nebula. I was in for a surprise.
I decided I would use the equipment I had as much as possible. I did not have confidence in using the 8se for exposures of 15 seconds because the C8 at 12.5 pounds was so close to the limit of the mount even for visual use. Instead of buying a new mount, I decided to use my C5 travel scope on the se mount. It weighs only 6 pounds. I felt like I would get better results with an equatorial arrangement so I did spring for the Celestron wedge which was on sale for $300.
I shot the Dumbbell nebula first for 20 minutes with 15 second subs. Then I shot the Ring Nebula for 8.5 minutes with 15 second subs. The Ring Nebula was captured pretty well (see photo), but I didn’t have nearly enough subs for the Dumbbell Nebula. My C5 with the Reducer/Corrector is F6.3 and the SeeStar is F5 and 10 minutes of the Dumbbell with the filter on with the SeeStar was enough to get a good image. I had figured something wrong. After more experiments I realized that all things considered, noise, etc. my QHY5II715C was one tenth as sensitive as the 462 sensor in the SeeStar. So I shot the Dumbbell again with an Optolong CLS filter for 4 hours (offset 30 gain 120, see photo). By my calculations I would have to shoot the Crab Nebula for 10 hours with the QHY5II715C. Instead of that, and to prove I was right about the relative sensitivity of the 715C vs the 462C sensor, I bought a QHY5II462C and used it for a one hour exposure (also with the CLS filter offset 10 gain 240, see photo).
I hope you find my experimental results useful.
