Another short test, this time of M51 with the ASI1600MM-Cool (cooled to -15C). I shot a few more frames than of M13, but the seeing was poor unfortunately. The image contains 2000 frames x 1 second stacked in AS!2.

I'll probably try again sometime, or perhaps combine this result with my earlier M51 image that shows some more details (but much small FOV)

click for full version

p.s. I used a cheap skywatcher coma corrector. Quite tricky to set up, but it does seem to work better. Perhaps a more expensive one can be justified at one point or another...

p.s.2 No filter was used

equipment used
40 cm Dobson made by Rik ter Horst
ZWO ASI1600MM-Cool