By Jim King

This is a series of columns primarily revolving around observing the Messier Catalogue.  The intent is to provide the reader a sampling of the Messier objects each month that are most visible in the time frame the column is published.  Hence, these deep sky objects should be easily identifiable in and around the month of August.  Some months may have a special treat in addition to the Messier Objects.  Check the trailer. 

M21: Open Cluster

The 2 degree-wide expanse of Milky Way encompassing M08, M20, and M21 is the most dramatic Messier field in the entire sky. At 23x, these objects and several other clusters and nebulous patches (both bright and dark) fill the field. 

Such a tight alignment might be nothing more than chance.  M08 and M20 are possibly part of the same complex.  Even though M20 and M21 are separated by about 1,000 light years, both should be observed and studied together because they appear to belong to the same celestial microcosm.

Messier notes: M21.  (Observed June 5^th, 1761) Star cluster close to [M20].  The known star closest to these two clusters is the seventh magnitude Flamsteed 11 Sagittarii.  The stars in these two clusters are eight and nineth magnitude and are surrounded by nebulosity.

NGC note: Cluster, pretty rich, little compressed, stars from magnitude 9 to 12.

Data: Messier 21, AKA: NGC 6531

Con: Sagittarius                                            Mag: 5.9

RA: 18h04.2m                                               Dec: -22.30

Dist: -4,200 ly+-

M08: Diffuse Nebula and Cluster

Messier notes: Observed May 23, 1764.  A cluster of stars that appears to be a nebula when observed with a simple three-foot refractor; with an excellent instrument, however, one only sees a large number of faint stars.  Near this cluster is a fairly bright star, which is surrounded by a very faint glow; this is the seventh magnitude star Flamsteed 9 Sagittarii.  The cluster appears to be elongated in shape, extending from northeast to southwest, between to bow of Sagittarius and the right foot of Ophiuchus.

NGC note: A magnificent object, very bright, extremely large, extremely irregular in shape, with a large cluster.

Data:                     Messier 08:  AKA NGC 6523, AKA Lagoon Nebula

                                Con: Sagittarius                                                                                             Mag: 4.6 (3.0 O’Meara)                

                                RA: 18h03.8m                                                                                                Dec: -24.23

                                Dist: -5,200 ly

M20: Nebula and Cluster

Messier: (Observed March June 6, 1764) Star cluster slightly above the ecliptic, between the bow of Sagittarius and the right foot of Ophiuchus

NGC: A magnificent object, very large and bright, Trifid, a double star involved.

Data:                     Messier 20: AKA NGC 6514, AKA Trifid Nebula or The Clover

                                Con: Sagittarius                                                                                                             Mag: 6.3 (cluster)                           

                                RA: 18h 02.5m                                                                                                              Dec: -23.02

                                Dist: 5,400 ly                                                                     

August Bonus: Saturn and Jupiter in a 6-month journey to a conjunction culminating in December.

Our two most observable planets begin a long-term hook-up in the early evenings beginning late June. 

Keep Looking up!!

Jim King

Field Trips and Observing Chair

Want more? Check out the HAS website under “Programs”/Messier Challenge