Hartl-Dengl-Weinberger 2 in Cassiopeia
HDW 2, also listed as Sharpless 2-200 and PNG 138.1+04.1, is an extremely faint planetary nebula. The region is suffused with very faint Ha areas, most prominent at lower left but present at lower levels in other areas of the image. A very small, faint patch of nebulosity, visible in both the Ha and OIII layers, glows around a faint star at lower left. Ha was used for red, and blended at low levels into blue and green. OIII was blended into blue and green at higher levels than the Ha. Blue was boosted further in the final image.
Optics/Mount: CPC1100 with f6.3 Celestron reducer on a Milburn wedge. Dec antibacklash set to 27/27. PEC on.
Exposure: Total exposure time about 41.7 hours; 93 x 20 mins Ha, 32 x 20 mins OIII. All bin 1x1.
Filters: Astrodon 5nm Ha and 3nm OIII
Date: Data was collected over 24 nights in November 2015 and from August to November 2016.
Imaging automation and capture: Sequence Generator Pro
Guiding Hardware: ASI120MM, Celestron off axis guider. Guiding scale 0.46 arcsec/pixel. 1 second guide exposures.
Focusing: Rigel Systems GCUSB/nStep on stock C11 focuser
Guiding Software: PHD2. RA aggressiveness 55, hysteresis 0, Minimum Move 1.4 arcsecs, Max RA 200, Max Dec 600. Guiding unbinned with ZWO connection. Dec set to hysteresis. Dithering set to Extreme with Settle < 1.2.
Guiding performance: Fairly good, with HFRs often around 1.5 arcsecs.
Light pollution: Bortle 8 (white zone, NELM about mag 4.5)
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50% reduction)
Processing: Bias, darks, and flats. Stacked and processed with PixInsight, with a few minor modifications in Photoshop.