With the milky way swinging up in the East above 30° around 11:30 pm, I only have three to four hours of narrowband nebula imaging time. Spring is “Galaxy Season” after all, with most of the northern hemisphere night sky time directed away from our own galactic core and into the depths of the known universe. You know, where many of the other galaxies are.
The skies weren’t particularly clear last night, but good enough for some long exposure hydrogen-alpha imaging of the Pelican Nebula (IC 5070) in the constellation Cygnus. The Pelican is the next-door neighbor of NGC 7000, the North America Nebula. With an 800mm focal length and the ZWO ASI1600MM camera I can fit most of the nebula into the frame, a nice clear view of the star-forming structures on the north-facing side, the “top” of the nebula.
Notes: when you’re shooting five-minute subs, the chances of something happening during any particular exposure go way up--satellite passing through, gust of wind, unanticipated guide corrections from poor seeing, clouds, and other events that affect the image. I shot 49 subs last night and this morning, before stacking, I went meticulously through each and threw out any that had elongated stars, contrast loss (probably clouds), and other artifacts captured during the run. I ended up stacking 38 frames with dark and bias calibration frames (no flats). But that's 38 good frames. Weather: seeing and transparency were poor, and really affected guiding, but still worth spending the time to capture enough data to process. The result is fine. I suspect, the results would be worse with OIII data--OIII being in the middle of the visible part of the spectrum and is probably more susceptible to light pollution, reflection off clouds, ambient temperature changes.
The Pelican Nebula in Cygnus (IC 5070), 3nm Ha filter, 38 x 300-second exposures stacked in DSS, shot with a ZWO ASI1600MM-Pro monochrome camera running at -10C. IC 5070 is part of the larger North America nebula region, about 2600 lighyears away.
May 26 update: IC 5070 in Cygnus in HOO narrowband (Hydrogen-alpha and Oxygen 3 mapped to RGB, with OIII taking both Green and Blue channels). Here's the info on the data I captured: 38 x 300-second Ha 3nm frames, 48 x 300-second OIII 3nm frames with the ZWO ASI1600MM-Pro monochrome camera, cooled to -10C. A little over 7 total hours of data gathering for this one.