My permanent observatory in Longueuil
in white light pollution zone
|Telescope||Celestron Edge HD - Diameter 203mm (8``), focal length 2032mm, f / 10|
|Focal reducer||f / 6.3 (63%)|
|Imaging camera||Atik 383 L + monochrome regulated at -20o Celsius|
|Autoguiding camera||ZWO ASI 120MM with one optical splitter|
|Auto Guidance Accuracy (RMS)||2,21 ″ arc RMS (4,42 ″ arc total)|
|Image type||RVsB (RVsB)|
(Vs for synthetic green)
|Exhibition||Red (30 x 3 'bin 2 × 2), Blue (25 x 3' bin 2 × 2)|
|Image acquisition software||Maxim DL|
|Treatment||Photoshop and PixInsight|
|Traitements spécifiques||Create a synthetic green layer|
Create a synthetic luminance image using the RGB color image
|Object type||Spiral galaxy seen from the side "The knife blade galaxy"|
|Distance||56 million light years|
|Diameter||140000 light years|
|Dimension seen from Earth||11,3 x 1,8 arc minutes|
|The galaxy NGC 5907 is a spiral galaxy seen from the edge. It is located about 56 million light years from Earth. Its diameter is approximately 140000 light years. It was discovered on May 5, 1788 by William Herschel. It is William Parsons who notices the disc and names it NGC 5907. Its very tapered shape earned it the nickname of "knife blade" (in English Knife Edge or Splinter galaxy) in 1970 by the amateur astronomer Walter Scott Houston. The galaxy is mainly composed of white dwarf stars and small, dense stars at the end of their life.|
In a site without light pollution, the galaxy is visible only using a large diameter telescope of 250 mm and more. It then looks like a thin knife blade, hence its nickname. The photo brings out a lot more detail, including a glowing core and a prominent dark dust band.
In my image, which was taken in a site of extreme light pollution (white area), we see with astonishment that the galaxy has been very well resolved! I photographed it without a light pollution filter! I opted instead to use short exposure times and take a lot of images to benefit from the following formula: Increase in Signal / Noise ratio = √ number of images. The short exposure times were calculated so as not to overexpose the sky background due to the significant light pollution of my observation site. As it is an object with a continuous light spectrum, I always make sure, before taking the photo, that its surface gloss (in mag / arcmin2) is equal to or greater than 14 (brighter, smaller number 13, 12, 11…) since the surface brightness of my sky is evaluated at 15. The surface brightness of this galaxy being 13,8, it is therefore accessible at my observation site. Using this knowledge, I am always assured, before taking the photo, that I will capture enough signal from the object! For those interested, I explain in detail this imaging technique in a sky of light pollution. See the following link:
In my image, we can also see a very small galaxy at the bottom right. It is cataloged PGC54419. It is located approximately 49 million light years from Earth and its diameter is approximately 10000 light years. Its dimension, seen from Earth, is only 54 x 31 arc seconds. Its visual magnitude is only 15,34, at the limit of the surface brightness of the sky background of my observation site!
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"