Galaxy
M100 (M100)
In Coma Berenices (Com) • Magnitude 9.3 • 7.4 arcminutes
Open the free AstroPlanner with M100 pre-selected, scored against your telescope, location, and the live cloud forecast.
One of the most photogenic face-on spirals in the Virgo Cluster, with prominent grand-design spiral arms. In 1993 it served as Hubble Space Telescope's "vision test" after its corrective optics were installed — the before-and-after images became one of the most celebrated demonstrations of what the telescope could do.
M100 at a glance
| Catalog IDs | M100, N 4321 |
| Type | Galaxy |
| Constellation | Coma Berenices (Com) |
| Right ascension | 12h 22m 55s |
| Declination | +15° 49' 12" |
| Apparent magnitude | 9.35 |
| Surface brightness | 13.3 mag/arcsec² |
| Angular size | 7.4 × 6.3 arcmin |
| Max altitude at 45°N | 61° |
| Best imaging months | Dec, Jan, Feb |
How to image M100
M100 sits in the constellation Coma Berenices at right ascension 12h 22m 55s and declination +15° 49' 12". To frame and integrate it well, AstroPlanner will compute the optimal moonless window for tonight from your location, the field-of-view fit against your sensor and focal length, the suggested total integration time given your aperture and sky Bortle class, and a cloud-aware schedule that drops it from the plan if your nearest cloud forecast spike overlaps the best altitude window. As a galaxy, M100 needs the darkest skies you can find: surface brightness, not just apparent magnitude, drives whether it will lift out of the gradient.