Round artifacts on image from Celestron Edge HD 8 Celestron EdgeHD 8" · Michael W. Dean · ... · 6 · 399 · 1

James Peirce:
They are out-of-focus dust/debris, probably thereabouts the reducer, filters, etc. This is what flats correct. They take on the shape of the aperture when out of focus, just as stars do.

James Peirce:

Michael W. Dean:

James Peirce:
They are out-of-focus dust/debris, probably thereabouts the reducer, filters, etc. This is what flats correct. They take on the shape of the aperture when out of focus, just as stars do.

Thank you. 

Will open all up and clean, then put back together and try again, THEN shoot new flats. 

Not using a filter, edited to add that. 

Have you seen this particular issue with your gear?

This is normal. The slower the focal ratio, the more prominent these motes display. The size in the image is relative to the aperture, the size of the debris, and the position of the debris in the optical path. It can be tricky to remove all of them and it is easy for more to turn up when things are disassembled. Especially on a telescope like this.

Note that your flats are meant to model these defects. You want the same defects in place for flats that were in place for the lights the flats correct. If you clean the optical path and take new flats, those flats will not correct these issues. Same goes if the camera was detached, rotated, etc. Even driving around can jostle dust. So always capture the flats corresponding to the imaging and capture new flats if the optical path is changed (e.g. for each filter as swapped or for each filter in a wheel, when the camera is rotated, etc).

It is worth reading up on some tutorials and the like to fully understand calibration frames. Good flats and the like play a very important role in quality of results. Good luck!

P.S. You mentioned the moon. You don’t want it anywhere close to where you are imaging such that it can either shine *or reflect* into the optics. That creates its whole new range of light gradient issues. So best to just pick a different target if the moon is nearby. Light leaks are also an increasingly more prominent issue with the moon out.