Globular Cluster in Hercules



M92: A globular cluster is a group of ancient stars (M92 is thought to be almost as old as the universe, perhaps 12 - 13 billion years old), gravitationally bound to each other. M92 is about 27,000 light years from Earth and is roughly 100 light years across. It contains as many as several hundred thousand stars, and shines relatively brightly at magnitude 6.4 (visible to the naked eye under the very best conditions).


This is the "first light" image with this scope, on the first night out with the scope.

Technical Information:

LRGB: 44:30:30:30 (L-11x4 min; RG&B-3x10 min). All images were unbinned.

Equipment: Meade 12" RCX400 at f/8.5, an SBIG ST-8XE camera/CFW8 color filter wheel with Astrodon filter set, guided by an SBIG AO-7 adaptive optics device, guiding at about 6 Hz (luminance) and 3 Hz (RGB).

Image Acquisition/Camera Control: CCDSoft V5.

Processing: All images calibrated (darks, dawn flats and flat-darks) and registered in CCDSoft. Luminance layer average combined in Ray Gralak's sigma reject program; R,G and B median combined in CCDSoft. Two iterations of Lucy-Richardson deconvolution routine applied using CCDSharp. Color combine, very gentle unsharp mask on the luminance layer, and adjustment of curves and levels, performed in Photoshop 6.0.

Location: All images taken from my yard in Redmond, Washington, USA, elevation 500'.

Date: All images taken on the night of June 21, 2005.

CCD Temperature: -20C

Moon Phase: Full moon

Seeing: Good, with 2.8 Arcsecond average FWHM in single calibrated image, deconvolved to 2.2.

Transparency: Very poor

Image Scale: .793 arcseconds per pixel

Copyright 2005 Mark de Regt

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