M91 (NGC 4548) Observation Guide — Barred Spiral Galaxy in Coma Berenices

Overview

M91 is a Barred Spiral Galaxy located in Coma Berenices, cataloged as NGC 4548. With an apparent magnitude of 10.2, it lies About 60 million light-years from Earth. This Advanced-level object is best observed in the Spring sky.

Barred spiral galaxies have a bar-shaped structure crossing through their center, with spiral arms extending from the ends of the bar.

Basic Data

Item	Data
Messier Number	M91
Catalog Number	NGC 4548
Object Type	Barred Spiral Galaxy
Constellation	Coma Berenices
Apparent Magnitude	10.2
Distance	About 60 million light-years
Best Season	Spring
Difficulty	Advanced
Required Equipment	Medium telescope

Physical Characteristics

This galaxy is located About 60 million light-years from Earth with an apparent magnitude of 10.2.

While there are estimated to be hundreds of billions of galaxies in the universe, those in the Messier catalog are relatively bright and representative objects observable with amateur telescopes.

Observation Guide

How to Find

M91 is located in the Coma Berenices region. It transits around 20:00–22:00 during Spring, making it well-positioned for observation. use the main stars of Coma Berenices as guide stars and confirm the exact position with a star chart or app.

Observation Tips

Galaxy observation benefits from dark skies and large-aperture telescopes. Use low magnification for a wide field of view, and allow your eyes to fully dark-adapt before observing.

Recommended Equipment

We recommend observing from dark skies with a telescope of 80mm aperture or more.

Astrophotography Tips

M91 is a popular target for astrophotography. Tracking with an equatorial mount is essential. Long exposures (30 seconds to several minutes) at high ISO reveal details invisible to the naked eye. Stacking multiple images reduces noise and produces beautiful, detailed results.

Summary

M91 is a Barred Spiral Galaxy observable in Coma Berenices, rated Advanced level. While it requires a somewhat larger telescope, it is a rewarding object to observe. Try observing it in the Spring night sky!