Hercules star cluster, and star-hopping to it

Event Date: February 4th

Time: 5:00 AM

Brief

  I have not looked at too many star clusters for this blog since starting it.  However for globulars ones, we are reaching a time of year for which two of them are seen in morning skies.  I will show what is perhaps the most popular one through a telescope this morning, and another one tomorrow.  M-13, known as the Hercules cluster (in the namesake constellation) is spectacular in large, powerful telescopes, yet can also be enjoyed in small, 6 or even 4" amateur 'scopes.  The cluster is found within the asterism keystone, which outlines the torso of the strongman.  In in the image below, is the cluster magnified a little less than 100x.

Detailed

   In the second image that I will show, I included his constellation and emphasized in bold lines, the keystone.  Also, I labeled the stars Vega, Deneb and Gienah; that's right, not Altair for now, as the 3rd summer triangle star (more on that in a couple of days).  The latter may not be familiar to you, yet look at where it is in relation to Deneb: part of Cygnus the swan's wingspan!  Despite this, Gienah's position in relation to Deneb doesn't really matter; its position to Vega does however.  If we imagine a line connecting Gienah and Vega and continue just as straight eastbound (in celestial longitude or simply upward), that line would directly hit the Hercules cluster.  Therefore, if you see both stars up, this is the way to find it.  See below:

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

  Finally, I will mention that the cluster can even be found when it is about to set and the stars are high in western half of the sky: the orientation of the swan's shape may change somewhat, but the stars are still positioned the same relative to each other!