Target guide · spiral galaxy
M91 with a smart telescope
M91 is a spiral galaxy about 5 arcminutes (0.08°) across, magnitude 10.2. It is highest around midnight in March, well placed from both hemispheres, and faint and spread out; it really benefits from a dark site and a long total exposure. It is larger than every native frame we track, or too small to fill one, so plan a mosaic or a crop.
Key facts
| Catalogue | M91 |
|---|---|
| Type | spiral galaxy |
| Apparent size | 5′ × 4′ |
| Magnitude | 10.2 |
| Position (J2000) | RA 12.59 h, Dec 14.5° |
| Highest at midnight | March (±2 weeks) |
| Sky needed | Dark sky |
In the best-matching frame
Imaging tips
Galaxies shine in broad starlight, so light-pollution filters help little. What helps most is a darker site and a long total exposure: plan on one to three hours of stacking for the faint outer parts. M91 is a target for your darkest nights.
Which smart telescope frames it best
| Telescope | Field of view | Fit |
|---|---|---|
| Unistellar Odyssey | 0.75° × 0.56° | small in the frame |
| Unistellar Odyssey Pro | 0.75° × 0.56° | small in the frame |
| ZWO Seestar S50 | 1.29° × 0.73° | small in the frame |
| Celestron Origin Mark II | 1.32° × 0.75° | small in the frame |
| DWARFLAB DWARF mini | 2.13° × 1.2° | small in the frame |
| ZWO Seestar S30 | 2.14° × 1.21° | small in the frame |
| ZWO Seestar S50 Pro | 2.45° × 1.38° | small in the frame |
| Vaonis Vespera II | 2.5° × 1.4° | small in the frame |
| Vaonis Vespera 3 | 2.5° × 1.4° | small in the frame |
| Vaonis Vespera Pro 2 | 1.6° × 1.6° | small in the frame |
| DWARFLAB DWARF 3 | 2.93° × 1.65° | small in the frame |
| ZWO Seestar S30 Pro | 3.99° × 2.24° | small in the frame |
How high it gets from where you live
Highest altitude above a flat horizon. Below about 20° the image suffers from haze and light pollution; trees and roofs often block it completely.
| Latitude | Highest altitude |
|---|---|
| Oslo, 60° N | 45° |
| Amsterdam, 52° N | 53° |
| Madrid, 40° N | 65° |
| Miami, 26° N | 79° |
| Equator | 76° |
| Sydney, 34° S | 42° |
Nearby in the sky
Objects close to M91 in the sky, so you can image them in the same session.
Questions and answers
- Can I photograph M91 from a city?
- It is hard: it is faint and spread out; it really benefits from a dark site and a long total exposure.
- Which smart telescope is best for M91?
- None of the smart telescopes we track frames it well in one frame; plan a mosaic or a crop.
- When is the best time to photograph M91?
- It is highest around midnight in March and well placed from both hemispheres. From 52° north it climbs to about 53° at most.