| Name | Webb's Cross |
| Designation(s) | M21, NGC 6531 |
| Object Type(s) | Open Cluster |
| Relevant Catalog(s) | All (Chron), Messier, NGC |
| Obs. Lat/Long | 42° 17', 073° 57' |
| Constellation | Sagittarius |
| Date and Time Observed | 2024-05-25 00:28:00 |
| Instrument | EdgeHD 8" f10-2,032mm FL |
| Camera | ASI294MC-Pro |
| Image Details | Up is 271.0 degrees E of N. Total integration time was 4m 15s. Exposures 15s@305g, UV/IR Cut Filter. Darks subtracted, no flats. Dithered and recentered in SharpCap. No guiding. |
| Description | This small, open cluster was discovered by Messier (ninth object overall) and was recorded on July 5, 1764. <--> M21 is a tiny open cluster located next to the Trifid Nebula (M20, see annotated view in gallery) on the edge of the rich Sagittarius star-field.. This is one of those objects of interest to Messier creating a list of "not comets" but has little visual interest to me except in combination with other objects or background. The gallery offers three views: 1) The principal image is a narrow field view captured with my EdgeHD. It shows the details of cluster well, but none of the context. 2) a more recent medium-field image captured with my Seestar. It shows the dark nebula and star field much more clearly. 3) A wide-field view showing M21 and M20 in context. |
| Related Observations | M21 (2) |
| Catalog Links | |
