I am not 100% sure, but I think it was captured with both Deepsky and 495nm Longpass. I think I still have focusing problems(?), among others ...
Yes, it appears that focusing still needs some work. Don't be discouraged though. With any new setup it takes time to learn all the sweet spots for focusing, etc. Once you've gone through the exercise a couple times it will become easier. For sure use the Bahtinov mask as it will make life much easier. I make a point of going to one of the brightest stars out at the time as part of my initial mount alignment routine. While there I get my focus spot on. Using very narrow filters plus the additional attenuation of the focusing mask can make the signal very low so you need a very bright star to focus with. Since you are using M51 as your test target, maybe use Arcturus as your focus star as it is relatively nearby in the sky. It is worth the time to GOTO the star to refocus when you change filters, then GOTO the target object when done. It seems tedious but will be much easier in the end.
You have an interesting complication, that your filter forms part of your spacers to the focal reducer. This will make it difficult to determine the impact of the filters on exposure time as your f-ratio will be different between configurations. Is there any way you can set the spacing independent of your filter selection? Can your filters go on the end of the FR closest to the telescope? I agree that sometimes due to reflections it is better to put the filter in between the camera and FR, but for your testing it will be much easier to just have the filters on the end of the FR.
Keep up the good work, and good luck!
I will need to work on focusing skill. At this stage, I don't know how much the bloating was due to focusing or due to wide bandwidth. With the 495nm Longpass and Deepsky stacked, only 495nm-530nm and 630nm + should have been passed. In terms of bandwidth, that would have been 25nm wider than a 610nm Longpass, but 80nm wider than IR 685 nm pass . The trade off is between brightness or number of stars detected versus bloating. At this point, filters are designed for either visual or long exposure imaging. With long exposure imaging, one can target a galaxy such as M51 and block everything with shorter wavelengths. With EAA, one need to detect enough stars, perhaps beyond the IR range, for Live Stack to work.
I will move the filter in front of the focal reducer in the next test.
One other thing, I don't understand the notion of Gamma and Brightness in Sharpcap. As I shortened the exposure, I had to move Gamma or Brightness to the right (increase). This is a learning experience for me, and it feels like peeling an onion, one layer at a time.
Edited by StarCurious, 30 March 2016 - 03:10 PM.