| Date 2021/06/17 and 18 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 with one optical splitter |
| Auto Guidance Accuracy (RMS) | June 17 0,99 '' arc RMS (1,98 '' arc total) June 18 1,96 '' of arc RMS (3,92 '' of arc in total) - Night with wind gusts over 20 km / h |
| Image type | Ha (Ha-OIII-OIII) |
| Exhibition | Ha (13 x 10 'bin 2 × 2), OIII (7 x 10' bin 2 × 2) |
| Image acquisition software | Maxim DL |
| Pretreatment | Maxim DL |
| Treatment | Photoshop and PixInsight |
Object description
| Object type | Emission nebula and open cluster "The Cocoon Nebula" |
| Constellation | Swan |
| Visual magnitude | 7,2 |
| Distance | 4000 light years |
| Diameter | 15 light years |
| Dimension seen from Earth | 12 arc minutes |
| IC 5146 consists of an emission nebula and an open cluster located approximately 4000 light years from Earth in the constellation Cygnus. Its shape is reminiscent of a cocoon, an envelope that contains insects or a silkworm, hence its common name. It has a diameter of about 15 light years. It is located near the eastern edge of the constellation, near that of the Lizard, right in the Milky Way, one hour in right ascension from the North America nebula. Like other regions of star formation, it is distinguished by a bright red hydrogen gas excited by hot young stars and blue starlight reflected from dust at the edge of a molecular cloud. The bright star near the center of this nebula is only a few hundred thousand years old. It is especially this which illuminates the majority of the nebula and which brings out the very beautiful shades of red color of the nebula. In a sky of low light pollution, the nebula is visible in a telescope of small diameter. We will then only see the center of the nebula (the cocoon). It takes a large diameter telescope to bring out the faint nebulosities around the nebula. In my image, which was taken in a site of extreme light pollution (white area), we can see the very beautiful shades of the nebula in the color red. As it is an emission nebula which emits its signal mostly in hydrogen, I used my Hydrogen-Alpha (Ha) filter as a luminance image. At the same time, this filter is very effective in combating the significant light pollution of my observation site. To bring out the very faint blue nebulosities around the nebula, I used an Oxygen III (OIII) filter. The composition of the color image is Ha-OIII-OIII. The Ha filter for the red and the OIII filter for the green and blue layers. This made it possible to bring out the natural colors of the nebula while also bringing out the colors in the stars which approach their natural colors with the traditional RGB filters (red, green and blue). |
| Richard Beauregard Sky Astro - CCD My impression "We cannot be alone in this gigantic universe" |