M13 Great Hercules Globular Cluster


Chris Heapy

Macclesfield, UK

Scope: TeleVue NP127is
CCD: Atik490EX
Mount: Losmandy G11
Guide: TV Pronto + Lodestar
Image data aquired from my suburban back garden in Macclesfield, Cheshire.

Although I’ve shot this wonderful object many times previously it’s always worth re-visiting to see if I can improve on what I captured the last time. For this attempt I wanted to go deep – and so this LRGB image consists of 40 x 600second subs for a total of 6.7hrs exposure. There are difficulties when trying to do this, M13 exhibits an enormous dynamic range with a very bright core and faint outlying stars. Also, I found tuning the colour balance particularly difficult whilst trying to avoid unwanted colour bias. Of particular note in this image are the red giants (which appear as orange stars) and the few scattered blue giants. The largest of the background galaxies (ngc6207, upper-right in this image) is also well shown and if you look closely you can even see the blue star forming regions along it’s right-hand edge.