M 92

Click on the image to display it full screen
Date
2017/05/21 et 2017/06/13

Observation place
My permanent observatory in Longueuil
in white light pollution zone

Technical

TelescopeCelestron Edge HD - Diameter 203mm (8``), focal length 2032mm, f / 10
Focal reducerf / 6.3 (63%)
MountCelestron CGEM
Imaging cameraAtik 383 L + monochrome regulated at -20o Celsius
Autoguiding cameraZWO ASI 120MM in parallel with the Orion mini guide
Auto Guidance Accuracy (RMS)1,43 '' of arc (2,86 '' of arc total) and 1,89 '' of arc (3,78 '' of arc total)
Image typeL (RVsB)
Vs for synthetic green
ExhibitionLuminance (49 x 1 'bin 2 × 2), Red (30 x 2' Bin 2 × 2) and blue (29 x 2 'Bin 2 × 2)
Image acquisition softwareMaxim DL
Guidance softwarePHD Guiding 2
PretreatmentMaxim DL
TreatmentPhotoshop and PixInsight
Specific treatmentCreate a synthetic green layer

Object description

Object typeGlobular cluster 
ConstellationHercules
Visual magnitude6,5
Distance26000 light years
Diameter110 light years
Dimension seen from Earth14 arc minutes  
M92 is one of the brightest globular clusters in the Northern Hemisphere. It is often overlooked by amateur astronomers due to its proximity to M13 which is the most spectacular globular cluster in this hemisphere. M92 is also one of the oldest globular clusters. It is located 26000 light years from the solar system and is therefore a little further away than its neighbor M13. Its diameter is about 110 light-years. The concentration of stars in the cluster at its center is very high. The mass of the cluster is high. It is about 300000 times the mass of our sun! The cluster is approaching the Earth at a speed of 110 km/s.  

Visual identification of the cluster is quite difficult. To see it, you need a sky with little light pollution. It is then visible through binoculars and has the appearance of a diffuse whitish spot. You need a telescope of at least 200mm to begin to resolve the cluster.  

In my image, which was taken at my personal observatory located in a sky of significant light pollution (gray and white areas), I still managed to resolve the star cluster to the center. It should be noted, for this image, I did not use a light pollution filter! I opted instead to take a lot of images with short individual exposure times by taking advantage of the following formula: Increase in Signal / Noise ratio = √ number of images. Long live mathematics and astronomical calculations!
Richard Beauregard
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"