M108 — Surfboard Galaxy

About

A barred spiral galaxy in Ursa Major seen nearly edge-on, which gives it the nickname Surfboard Galaxy. It lies about 46 million light-years away by one measure, though a 2014 study put it nearer. Four supernovae have been recorded in it, and its central black hole is estimated at 24 million solar masses.

Imaging tips

• Long and thin at roughly 8′ × 2′: 3,030–5,050 mm on APS-C, though it is also often shot small inside a wide field.
• Surface brightness is 21.6 mag/arcsec². A 14-inch f/8.3 scope with a CCD spent over 5 hours on it, mostly luminance (215 of 305 minutes), with just 30 minutes per colour.
• The Owl Nebula (M97) can share a wide frame with it: one 8-inch f/3.9 astrograph got both in 3.5 hours of LRGB, and a RASA 8 in 9 hours of 5-minute colour subs.
• M97 is much brighter than the galaxy, so one imager wished for 180-second rather than 300-second subs to protect it. Best around February and March.