note added 05/08: the variation is not in each sub-image, but between the images. Basically, the sequence for these four is: picture #1 bright trail; picture #2 faint trail; picture #3 bright trail again; picture #4 faint trail again.
Apart from 07-027B, I also observed IGS 1B (03-009B) and a mag. -0.5 flare of Iridium 74 (98-032D). Around the time of the Iridium flare however, cirrus clouds moved in and I stopped observing.