| Date 2018/09/14 Observation place My permanent observatory in Longueuil in white light pollution zone |
Technical
| Telescope | Orion 80ED refractor - Diameter 80mm, focal length 480mm, f / 6 |
| 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) | 1,13 '' of arc RMS (2,26 '' of arc in total) |
| Image type | B (RVsB) Vs for synthetic green |
| Exhibition | Red (30 x 5 'Bin 2 × 2) and Blue (30 x 3' 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 | Spiral galaxy "The great Andromeda galaxy" |
| Constellation | Andromeda |
| Visual magnitude | 3,4 |
| Surface gloss | 13,5 |
| Distance | 2,55 million light years |
| Diameter | 220000 light years |
| Dimension seen from Earth | Dimension: 190 x 60 arc minutes |
| M31 is the brightest galaxy in the northern sky. It is the largest galaxy in the Local Group (our Milky Way being the second). It is the closest to ours. Its disc is twice as wide. It is easily visible to the naked eye or with binoculars. Despite the extensive studies of which it is the object, the Andromeda galaxy has not yet revealed all its secrets. It would not be the typical spiral galaxy it appears to be: for example, despite its considerable size, it appears less massive than the Milky Way, and its halo of dark matter is diluted. Nonetheless, astrophysicists have calculated that its central black hole is 30 million solar masses, ten times that of the Milky Way. The enormous mass of this black hole is surprising, because, as a rule, the black hole of a galaxy is supposed to mirror the mass of its parent galaxy. In addition, analyzes in different wavelengths revealed a discontinuity of the galactic disk, which would be due to a collision with one of its satellite galaxies in recent millions of years. M31 and our Milky Way are approaching each other at a speed of 100 to 140 km per second: they should collide and merge together within 5 billion years. Until then, we have plenty of time to live our lives and allow our children, grandchildren… to enjoy our beautiful, comfortable planet, provided of course that we protect it well. We can see on the photo towards the bottom right the galaxy M110 which has a magnitude of 8,1 and an apparent dimension of 17 'x 10'. We also see the galaxy M32, the white point that is stuck on the arm of the galaxy, slightly to the left.It also has a magnitude of 8,1 with a visible dimension of 8 'x 6'. So we see 3 galaxies in this photo! One can appreciate the grandeur and even the enormity of the Andromeda galaxy compared to the other two. In the photo presented, which was taken in a site of extreme light pollution (white area), it is surprising to have succeeded in solving the galaxy very well, considering the low light of its spiral arms. Also, the majority of astrophotographers do not bother to photograph galaxies in a sky of significant light pollution, considering the great difficulty of solving these objects in this type of sky. As the luminance image, I chose the monochrome image taken with the blue filter, because it was this which provided the most beautiful details and contrasts in the galaxy. No wonder, since the spiral arms of the galaxy are in blue tones. Each individual image (red and blue) was taken with maximum exposure time, just before the sky background was overexposed. This allowed the Signal to Noise (S / N) ratio to be maximized for the individual images. Then, I added (composed) a large number of images (30 for each of the red and blue images), which also served to increase the S / N ratio, while decreasing the background noise of the sky. For the color image, I produced a synthetic green using the red and blue images, which resulted in an RGB color image (Vs for synthetic green). |
| Richard Beauregard Sky Astro - CCD My impression "We cannot be alone in this gigantic universe" |