Tuesday, June 12, 2018

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.

stars to the north-east from CAO

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...

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.

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