Downloadable Deep Sky Field Guides at Amazon (click book cover for info.)

How to Use Reference Line Maps to locate deep sky objects.

Observer Notes:

1. Ptolemy, observing from 31 degrees north at Alexandria, first catalogued M7 in his Great Syntaxas.  Ptolemy’s catalog was compiled over a period of 24 years, from 127 A.D. to 151 A.D.
2. Ptolemy recorded 6 nebulous objects in the Great Syntaxas.  Three turned out to be asterisms.  Two of the remaining three, M44 and the Double Cluster in Perseus, had been catalogued previously by Hipparchus.
3. The Coma Berenices open cluster is the remaining nebulous object first recorded in the Great Syntaxas.

Credits, Links & Resources:

1. The images of  galactic position of eemission nebulae, star clusters and planetary nebulae relative to our own Sun  are provided courtesy of thinkastronomy.com.
2. A complete online resource for  distances, sizes and locations of deep sky objects is available at seds.org.
3. Sky and Tleescope’s This Week’s Sky At A Glance is worth checking before every stargazing session.
4. Danko’s  Clear Sky Chart provides a 48 hour forecast of observing conditions for every  location  in North America.
5. Reference Line Maps are produced by Project DeepSkyMap, a collaborative venture of observers who enjoy  knowing the heavens and  locating objects for themselves.