M13, with a 4 inch refractor

M13, The Great Globular Star Cluster in Hercules
Sketch and Details by Rony De Laet

M13 has always been one of my all time favourite deep-sky objects. This Globular is one of the summer highlights for Northern Hemisphere observers. It is bright and it is easy to find. When conditions allow, a four inch telescope is capable of resolving many stars within this spectacular globular. The low power view reminds me of little hairy spider. The cluster seems to show several branches attached to a mottled and fractured core. The core appears slightly yellow to me. With higher power and averted vision, these branches can be partially resolved into faint stars. Then with prolonged gazing, the cluster appears to show a few dark lanes as well. It is a hard task to do justice to this cluster with a sketch : the real view is so much more powerful. I tried to represent the typical low power view, with many faint stars at the verge of resolution.

Site : Bekkevoort, Belgium ( 51° N )
Date : May 29, 2009
Time : around 23.00 UT
Scope : Skywatcher 102/500mm achromatic refractor
Eyepiece : Baader Hyperion 5mm
Magnification : 100x
FOV: 41’
Filter : none
Seeing : 3/5
Transp. : 4/5
Sky brightness : 19.88 magnitudes per square arc second near zenith (SQM reading).
Nelm: 5.6
Sketch Orientation: N up, W right.
Digital sketch made with Corel Paint Shop Pro X2, based on a raw pencil sketch.

Rony De Laet