Messier 92 is a globular cluster of stars in the northern constellation of Hercules. M92 is one of the brighter globular clusters in the northern hemisphere, but it is often overlooked by amateur astronomers because of its proximity to the even more spectacular Messier 13. It is visible to the naked eye under very good conditions. M92 is at a distance of about 26,700 light-years away from Earth.
Among the Milky Way population of globular clusters, Messier 92 is among the brighter clusters in terms of absolute magnitude. It is also one of the oldest clusters. The half-light radius, or radius containing half of the light emission from the cluster, is 1.09 arcminutes, while the tidal radius is 15.17 arcminutes.
This image also features NGC 4645, an elliptical galaxy located around 121 Mly from Earth. It has a magnitude of 11.68 & a surface brightness of 21.6. It is the the lower right of the image.
Data captured 11 October, 2017.
34x 4 minute exposures at ISO400.
Skywatcher Quattro 200 CF
Canon 40d (IR Filter removed)
This image was processed in Pixinsight & Lightroom.
Calibration and Stacking in Pixinsight.
Dynamic Crop - To remove black edges & integration artifacts.
Automatic Background Extraction - To remove gradients.
Canon Banding Reduction script - To remove horizontal lines.
Photometric Colour Calibration - To colour calibrate the image.
SCNR - To neutralise green.
Multiscale Linear Transform - Noise reduction.
Histrogram Transformation - To stretch the image and bring out the data.
TVGDenoise - Noise reduction.
HDR Multiscale Transform - To recover additional data in core, with star mask applied.
Local Histogram Equialisation - To sharpen and increase detail, with star mask applied.
Multiscale Linear Transform - To sharpen and increase detail, with star mask applied.
Export as JPEG and import into Lightroom.
Clip Blacks (-25)
Increase Saturation (+50)
Graduated Filter to reduce gradient in lower right corner. Exposure (-0.5)
Export final JPEG for upload.