• NGC 4548 or Messier 91 in Coma Berenices
    • M91
    Annotated image
  • Messier 91 is a barred spiral galaxy in the
  • Virgo Cluster of galaxies.  M91 is about
  • 64 Mly from us and 105.5 kly across.
  • Hover over the image for an annotated view.
  • Date:  7 April 2026
  • FOV:  cropped to 20' × 13' 20"; the apparent size
  • of M91 is about 5.4′ × 4.3′
  • Rotation:  0.002°
  • Telescope:  Orion 127mm Mak-Cass (1381mm, nominally 1540mm, f/12.1)
  • Guiding:  ZWO ASI120MM mini mono guide camera,
  • SVBony SV165 Mini 40mm f/4 guide scope
  • Computer:  ASIair pro Raspberry Pi
  • Mount:  ZWO AM5N
  • Camera:  ZWO ASI071MC Pro Cooled (-10°C) Color CMOS gain 90
  • Pixel size:  4.78 μm
  • Resolution:  0.714 arcsec/pixel
  • Filter:  none
  • Frames:  fifty-six 300 second subs
  • Total Time:  4 hours and 40 minutes
  • Calibration:  20 flats, 20 dark flats, and 20 darks
  • Processing:  Pixinsight – DBE, Color Cal with GHS, BlurXT, NoiseXT → Linear
  • MStr, GHS, HST, PMath MStr + GHS + HST → Stars, Sat,
  • StarXT, MStr, GHS, HST, PMath MStr + GHS + HST → Starless,
  • HDRMST866PhLm, Sat, PMath ~(~Stars*~Starless) → Blend, scale
  • Location:  Darling Hill Observatory near Vesper, NY