Sh2-173, The Phantom of the Opera Nebula

Sh2-173 is a moderately faint HII region in Cassiopeia. I actually took this image while waiting for my main target for the night, Simeis 147, to rise. But I’m pleased with the way that it turned out. Shooting at f/3.7 helps. Most images show only the central area, but there is a lot of interesting nebulosity in the surrounding area. To see the “face,” look at the image upside-down, and it’s a lot more apparent.

  • Exposures (-10ºC):
    • H-alpha: 46×180s (gain=100)
    • R, G, B: 20×90s each (gain=0)
    • Total exposure time:  3 hours 48 minutes
  • Taken from Doylestown, PA, Nov 3, 2022
  • Telescope: Takahashi FSQ-106ED with f/3.67 reducer
  • Camera: ZWO ASI2600MM-Pro with Astrodon filters (5 nm)
  • Mount: iOptron CEM60
  • Guiding: ZWO ASI174MM (off-axis)
  • Acquisition: NINA + PHD2 and ASTAP
  • Processing: AstroPixelProcessor, PixInsight

The H-alpha image is shown below.

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