On a night with pretty decent seeing, but a full moon, I decided to try revisiting this nebula, this time imaging it using a UHC filter (intended for visual observing) as a sort-of tri-band narrow-band filter (it passes the red H-alpha spectral line as well as the H-beta and OIII lines usually passed by UHC filters). I only got a couple of 8 minute live-stacked images before clouds came in and then fog formed, but it was enough data to produce a decent image. The inset shows a the nebula scaled up 200% to make the finer detail easier to see.
The nebula itself has fairly low red H-alpha wavelength (656nm) emission and so is mostly lit up by green OIII emission (500.7nm and 495.9nm) and blue-green H-beta emission (486nm). You can see a nice spectrum of the nebula here:
https://apps.williams.edu/nebulae/spectra.php?neb=NGC%201501Gaia data release 2 has an excellent parallax data for the central star of the nebula, giving an accurate distance to the nebula of 1000 / 0.5672±0.0253 (milli-arcsecond parallax) = ~1,762 parsecs distance. The nebula measures 61 x 43 arc minutes in this image, so this puts its size at close to 1.2 x 1.7 light years.
Each of the two images stacked for this image were themselves a live-stack of 320 x 1.5 second exposures, live-stacked in Sharpcap.
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