• Stephan's Quintet in Pegasus
    • Stephan's Quintet (Arp 319)
    Annotated image
  • Arp 319, or Stephan's Quintet, is a visual group of five galaxies.
  • The brightest galaxy, NGC 7320, is much closer to us and is not
  • a gravitational member of the group.  The other four galaxies,
  • NGC 7317, NGC 7318a, NGC 7318b (PGC69260), and
  • NGC 7319 are gravitationally bound.  NGC 7318a and
  • NGC 7318b are approximately 280 Mly from us.
  • Hover over the picture for an annotated version
  • Date:  2 and 29 August 2025
  • FOV:  cropped to 10' × 6' 40"; the quintet is about 5'
  • Rotation:  0.030°
  • Telescope:  Celestron C14 SCT (3910mm, f/11)
  • Starizona SCT Coma Corrector/Reducer (2648.4mm, f/7.5)
  • Guiding:  ZWO183 MC pro
  • Computer:  ASIair plus 256GB
  • Mount:  iOptron CEM120
  • Camera:  ZWO ASI2600MC Pro Cooled (0°C) Color CMOS with gain 100
  • Pixel size:  3.76 μm
  • Resolution:  0.293 arcsec/pixel
  • Frames:  9 × 300 seconds × 100 gain
  • Filter:  Optolong UV/IR cut
  • Calibration:  20 dark, 20 flat, 20 dark flat
  • Stacking:  twenty-three 300 second frames using PixInsight
  • Total Time:  1 hour 55 minutes
  • Processing:  Pixinsight – SPCC, DBE, SPCC, BlurXT, NoiseXT → Linear
  • HTS, GHS, MStr, PixelMath MStr + GHS + HST → Stars,
  • Linear, StarXT, HTS, GHS, MStr,
  • PixelMath MStr + GHS + HST → Starless
  • PixelMath ~(~Starless*~Stars) → Blend
  • Location:  Darling Hill Observatory in Vesper, NY