On the night of Oct 17/18, Loryn Zachariasen and I used the HDI camera on the WIYN 0.9-m telescope to take images of NGC 7790 through an R-band filter. All images were 5 seconds in length. The extracted subimages below are raw -- no processing has been applied.
We went very far from focus in both directions: best focus was about 32600 units, but these images were taken at focus positions 34000 and 31000. Each unit corresponds to 0.5 microns, so the images below were taken roughly 700 microns = 0.7 mm away from best focus.
The pictures below are closeups of the four corners of the CCD images. The first set of pictures show the same corner in the two different exposures (one too far inward from best focus, one too far outward from best focus). The second set of pictures shows the diagonally opposite corners in one exposure, then the diagonally opposite corners in the other exposure.
SouthEast
SouthWest
NorthWest
NorthEast
SouthEast/NorthWest
SouthWest/NorthEast