a lot of darks

I had hoped to image the northern or north-eastern sky for a protracted time, perhaps to capture the tumbling satellite a few of us have seen. So I set up my rig near the Observing Pad at the Carr Astronomical Observatory. And proceeded to make several mistakes.

I really didn't choose good exposure settings. The "light" frames are terribly underexposed. I had based my values on the star trails shots from 27 Aug '15 when I shot with the Rokinon 8mm lens at f/5.6, ISO 1600, and 30 seconds each frame.

When I configured my camera this time, I set the lens to f/8. Oops. This dramatically reduced the light reaching the sensor. The hot pixels are as bright as the stars. Distracting.

The bigger whoops was leaving the fisheye lens cap on. In my rushing to set up and not bug Chris M and Ian W on the Pad, I completely forgot to remove the cover. It wasn't until much later, after shoot over 200 stills, that I discovered my mistake. Well, I have lots of dark frames now...

I manually inspected the 69 light frames. No obvious bright flares, spinning satellites, fireballs, or the like.

Tech. info.: Canon 40D, big tripod, intervalometer, RAW collected, DPP, 16-bit TIFF files to Photoshop, manually subtracted dark, levels, curves.