Faint background stars

Visibility of faint background stars on the "movie" from a dozen of CCD frames vs. on the single frame. Also these background stars affect photometry of minor planets (0.01 mag added from a star 5 mag fainter than asteroid)!

single frame movie from 15 frames sum of 15 frames
single frame movie from 15 frames sum of 15 frames
Note also faint "wings" from a galaxy in upper left corner.

Peter Kušnirák, Ondřejov, 12/2006