NGC6888, the Crescent Nebula in Cygnus, taken with an AP 140 F7.5 Starfire EDF Astrograph Refractor with 4" focuser.
The instrument was working at F5.7 with the 155TCC Telecompressor Corrector.
STL11000 camera - 4 hours Ha, 4 hours of O-3 and 2 hours of S-2.
Although reduced to a manageable file size, this image is the full frame of the large STL11000 CCD chip.
Note the round, pinpoint stars at all four corners!
Image by Roland Christen.