M21 Observation Details
M21 Daily Motion
M21 will be visible throughout the entire night. It will rise at 23:48, just before twilight begins, and will be at 25° when twilight starts at 03:05. It will reach its transit at 28° at 04:26, and will fade away as twilight ends at 05:15, being at 27° elevation.M21 will be visible until January, 1, when it will move too close to the Sun. During this time, its proximity to the Sun will cause it to disappear from the night sky, making it unobservable for a while.
M21 Visibility Timetable on May 09
M21 Rise and Set Timetable
| Time | Elevation | |
| Moon Rise, 87.4% illuminated | 17:00 | -71° |
| Astrosession begin | 22:21 | -15° |
| M21 rise | 23:48 | |
| M21 transit | 04:26 | 28° |
| Astrosession end | 04:35 | 28° |
| Moon Set | 04:45 | 27° |
| Civil sunrise | 05:52 | 24° |
| Sunrise | 06:23 | 22° |
| M21 set | 09:04 |
Track M21 Position Throughout the Night
← Fri, 9 May 2025 →
| Time | |
| Altitude | |
| Azimuth |
M21 - Open Cluster
M21 is an open cluster located in the constellation Sagittarius. It was discovered by Charles Messier in 1764. The cluster contains a mix of young, hot stars and older stars.
M21 spans about 15 light-years across and contains around 57 stars. The cluster is approximately 4,250 light-years away from Earth and has an apparent magnitude of 6.5, making it visible with binoculars or a small telescope.
M21 Image Gallery
DSS Blue
DSS Red
DSS Near-Infrared
DSS Composite image
The photos are taken from the Digitized Sky Survey 2 (DSS2), which was produced at the Space Telescope Science Institute (STScI) under NASA contract, using data from the UK Science and Technology Facilities Council (STFC), the European Southern Observatory (ESO), and the National Geographic Society-Palomar Observatory Sky Survey (POSS II).
Special thanks to the National Optical Astronomy Observatory (NOAO), the Royal Observatory, Edinburgh, and the California Institute of Technology for their significant contributions.
Finder Chart for M21
| Object name | M21 |
| Field of view | |
| Limiting magnitude | |
| M21 coordinates | 18.0704, -22.49006 |
| Center coordinates | 18.0704, -22.49006 |
M21 Passage Through Night
Current position of M21
| Time | 03:05 |
| Latitude | 39.9625 |
| Longitude | -83.0061 |
| M21 elevation | 25° |
| M21 Azimuth | -159° |
Annual motion of M21
| Date | Sat, 10 May 2025 |
| Twighlight start | 22:18 |
| Twighlight end | 04:28 |
| Twighlight duration | 6h 10m |
| Rise | 23:44 |
| Set | 09:00 |
| Elevation at transit | 28° |
| Transit time | 04:22 |
| Equatorial coordinates | RA: 18h 04m 13s", Dec: -22° 29' 24s |
| Magnitude | 6 |
| Constellation | Sagittarius |
The graph is structured with the vertical axis showing the hours of the day, ranging from 12 AM to 12 AM the next day, while the horizontal axis spans each day of the year.
The reddish shaded area indicates the periods when the M21 is above the horizon, visible to observers. The white line marks the times when the celestial object reaches its highest point in the sky each day, known as the transit.
Data Credits
The nebulae information on this page is sourced from the OpenNGC project, developed by Matteo Verga. OpenNGC provides detailed data on the NGC catalog, which is a valuable resource for exploring deep-sky objects such as nebulae.
For more details or to contribute to OpenNGC, visit the official GitHub repository: OpenNGC on GitHub.