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The globular cluster M5 in Serpens Caput.  It is thought to be one of the oldest globular clusters, at 13 billion years. It's one of the largest globular clusters in orbit around out galaxy with a diameter of about 165 light years.  M5 is about 24,500 light years away.

Image info

Telescope:  Celestron 9.25" Schimdt-Cassegrain at f/6.3

Focus:  Prime focus

Filter:  Celestron LPR

Mount:  Vixen GPD with Skysensor2000

Camera:  Modified Canon EOS 300D, at ISO800

Guiding:  700mm refractor guidescope, SAC7 camera, autoguided with Guidedog software

Exposure:  Total 30 mins (20 x 90s)

Date:  5th February 2005

Processing:  RAW file conversion, Offset and Dark subtraction, flat fielding, registering and stacking done in IRIS.  Curve stretching and colour saturation enhancement by Luminance Layering in Photoshop CS.  The background had high colour noise in red and blue, so it was selected in Photoshop, and colour saturation reduced.


I am experimenting with imaging at ISO 800 with shorter individual exposures - rather than ISO 400 and 3 mins before.  Looks satisfactory and I have reduced the no. of frames discarded due to trailing, but it's too early to tell if image quality is any different.


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