Rhinottw

So, mount and scope is in the yard and i had a chance to do some further experimentation in my pursuit to solve this. I think i am dealing with a spacing issue. I thought to myself that my method is good and i know it is working, what i did not think about is just because the FWHM value is as low as i can get it does not mean the camera is in focus. Turns out my camera adapter rings are not equally thick and i think this is the issue. I happened to have a 1mm and a 0.5 mm spacer rings that i fitted between the CC and the camera, this kinda helped and the stars improved a bit and the spikes got close together. So i tried unscrewing the camera a bit to further increase the distance to the CC and i got rid of the ring stars and the diffraction spikes came together. It is of course very tilted because of the camera is not screwed all the way in, but the star look much better in some parts of the image. I will order some additional spacers and try again when they get here.

Another image showing the same issue, i also get double diffraction spikes... :

Thank you for the welcome and input. Yes, the tilt is not the issue, i will have to deal with that sepperately, probably with a tilt-correcting adaptor, it is also in the Canon exposure. I use the FWHM assistant to get the value a small as possible and then i lock down the focuser. I then re-check the value to make sure it is has not changed, if it has i re-focus and lock again, repeat until i have the smallest value possible. This is working just fine for my Canon and has always been my focusing method since i started using backyard canon/nikon. This rules out focuser slip and focus shift from locking down the focuser. I believe the focus mode uses the livewiev from the camera and sends it to the computer, but i am not completely sure how it works technically. After this i do some test exposures - this is where the Nikon 40s exposure is from with the donut stars. The telescope sat outside for 30-40 minutes before i started polar alignemet and focusing, so i would guess at least 50min. to an hour of cooling down before the image was captured. This is extremely strange and i have not seen this before - this is my second season doing AP, so i am not completely new anymorem but not excactly an expert either this is just a mystery to me.

Hi all, I am having some troubles with my new(used) camera, a Nikon D5300. I have tried getting it to work for 2 nights now, but i am getting the same result each time with donut shaped stars. Example image: https://i.imgur.com/v1mpnXY.jpg - 40s exposure - After having captured this image i put on my tried Canon 450D and after re-focusing i got this: https://i.imgur.com/ITxUY7N.jpg - 120s exposure. I know i have a bit of tilt going on causing elongated stars in the lower left of the image, but it is really the donuts that bother me, the tilt can be corrected. My first intuition is that it is a focus issue and that i am seeing the secondary mirror in the middle of the stars. My issue with this is that the camera was focusd using Backyard Nikon and FWHM focusing assitant. When doing this there was no sign of the donuts and i could focus it just fine - like i have done several times before with my Canon. The only thing that was changed between the two images was the camera (and camera adpter). My optical train is TS Photon 6" (GSO) --> TSMaxfield Coma corrector --> M48 to camera adapter --> Camera. This is very puzzeling to me, since there should not be any difference between focusing and imaging from a focus perspective. Does anyone have any idea what could be goind on, could the camera be defective, i have not really used it much before this, only a few shots of daylight images that showed no issues. Any help would be much appreciated.