Date 2017/05/21 et 2017/06/13 Observation place My permanent observatory in Longueuil in white light pollution zone |
Technical
Telescope | Celestron Edge HD - Diameter 203mm (8``), focal length 2032mm, f / 10 |
Focal reducer | f / 6.3 (63%) |
Mount | Celestron CGEM |
Imaging camera | Atik 383 L + monochrome regulated at -20o Celsius |
Autoguiding camera | ZWO 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 type | L (RVsB) Vs for synthetic green |
Exhibition | Luminance (49 x 1 'bin 2 × 2), Red (30 x 2' Bin 2 × 2) and blue (29 x 2 'Bin 2 × 2) |
Image acquisition software | Maxim DL |
Guidance software | PHD Guiding 2 |
Pretreatment | Maxim DL |
Treatment | Photoshop and PixInsight |
Specific treatment | Create a synthetic green layer |
Object description
Object type | Globular cluster |
Constellation | Hercules |
Visual magnitude | 6,5 |
Distance | 26000 light years |
Diameter | 110 light years |
Dimension seen from Earth | 14 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" |