If you had to nominate one constellation as "best of" for northern deep sky observers, which would you choose? Virgo, with all of those bright galaxies and Messier objects? Scorpius, with its clusters and nebulae? Or perhaps Orion, with the most amazing nebulae available. I would argue Sagittarius. It has a reasonable number of NGC and IC objects (77), a consistently fine background when star hopping, plenty of worthwhile objects from other catalogs, and perhaps the widest variety of objects in any one constellation. There are open clusters galore, along with nearly as many globular clusters. There are planetary nebulae, galactic nebula, and even a few galaxies. Double and variable stars are positively glorious. I have yet to mention that there are no less than fifteen Messier objects!
Best of all, Sagittarius is a summer constellation and on view during the best observing weather for us northern folk. Trying to choose favourite constellations is a totally subjective exercise, as is choosing a favourite object in such a rich area. I won't even try, at least until I have viewed all of them. This may take a few seasons. The one disadvantage of observing in Sagittarius is its relatively low position in the southern sky. My latitude is 42 N. I can comfortably observe stars and clusters to about -35 degrees on excellent nights, and on occasion, for certain objects, I can reach -42 degrees. However, finding nights in the humid summer when I can clearly see the southern sky is difficult, and a rare occurrence. For that reason, I always have other, higher constellations on the go. I am working in Aquila, Delphinus and Sagitta most nights. However, if and when the southern sky is worthwhile, off I go to Sagittarius. So far I have barely begun my re-exploration of this amazing motherlode of deep sky treasures. For now, I am concentrating on the sky in and around M 23.
Here is a simplified list of what I will be observing in Sagittarius. Firstly, the fifteen Messier objects are: 8, 17, 18, 20, 21, 22, 23, 24, 25, 28, 54, 55, 69, 70, and 75. Have I missed any?
In the NGC list there are:
In the NGC list there are:
19 open clusters
21 globular clusters
03 galactic nebulae, plus 2 more involved with clusters and having the same designation
06 galaxies (from my latitude--there are several more, but too low for me to attempt)
11 planetary nebulae
In the IC catalogue are:
01 globular cluster
10 galactic nebulae
06 planetary nebulae
From other catalogues of interest to me are:
33 open clusters
04 galactic nebulae
I am also seeking a minimum of 15 doubles, some of which I have seen previously with the 8" and recorded as worth viewing again, along with a few I could not split with that instrument. Combined with my work in three other summer constellations, I am happily awaiting the last quarter moon phase and the next clear night closest to it.
Mapman Mike
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