M108 (NGC 3556) Observation Guide — Spiral Galaxy in Ursa Major

Overview

M108 is a spiral galaxy in Ursa Major, catalogued as NGC 3556. At Magnitude 10, it lies roughly 45 million light-years away. Spring evenings are best for viewing, and the object is suited to advanced observers.

Spiral galaxies have a central bulge surrounded by winding arms rich in young stars and interstellar gas — zones of active star formation.

Basic Data

Physical Characteristics

M108 sits about 45 million light-years away and shines at Magnitude 10. It appears nearly edge-on from Earth, showing a mottled, cigar-shaped disk with visible dark lanes.

Observation Guide

Finding It

M108 lies in Ursa Major, close to the star Merak (β UMa). Spring evenings around 8–10 PM put it in a favorable position. Use Ursa Major's main stars as anchors, then confirm the precise location with a star chart or app.

Tips for Observing

Dark skies and aperture are both critical for M108. Use low magnification and allow thorough dark adaptation before searching. The edge-on orientation and dark mottling are the visual highlights.

Recommended Equipment

A medium telescope under dark skies, with at least 80 mm aperture, is recommended.

Astrophotography Tips

M108 is a popular astrophotography target, often imaged alongside the nearby Owl Nebula (M97). An Equatorial mount, high ISO, and long exposures combined with image stacking reveal the galaxy's dust lanes and patchy disk structure.

Summary

M108 is an advanced-level edge-on spiral galaxy in Ursa Major — a challenging but visually distinctive spring target.