Catskills Fireflies (single exposure)
Something to do on a dark, mostly cloudy night:
Single 10 minute exposure at ISO800 with Canon T2i (550D) DSLR and Canon EF 50mm f/1.4 lens wide open at f/1.4. Focus was done on the background trees, and then moved inward to where most of the firefiles were expected. The camera was mounted on a fixed tripod, and was tethered to a laptop using a USB cable, and the 10-minute exposure was timed with EOS utility.
This shot is pretty much SOOC -- raw conversion to TIFF using Canon Digital Photo Professional, then downsizing and JPEG conversion with Photoshop (no levels, curves, sharpening, etc.). This is the full frame from the T2i. Image calibration (dark frames, flat frames, etc.) was not done, despite the 10 minute exposure and the resulting dark current noise and hot pixels.
The grass and trees are illuminated from light pollution (there was no moonlight), and possibly from the fireflies themselves. It was quite dark out -- the SQM-L reading was about 22.02 when this frame was taken. This unusually dark reading was presumably caused by low clouds overhead, which block out most of the upper level light pollution from distant cities (like NYC) . It was actually party cloudy, and the SQM-L reading between clouds was the more usual 21.4 to 21.5 that night.
Imagine trying to do astroimaging through these swarms of fireflies during firefly season. A narrowband H-alpha filter does make them almost invisible, however.