M31 (published January 2010)

Copy of the original post in my old blog, made in January 2010 (My old blog can be seen here).

The idea of this image started as a project in collaboration with Dr. David Martinez Delgado (Instituto de Astrofisica de Canarias). The main aim was to explore the sensitivity of my equipment in the detection of dwarf satellites and faint diffuse light features (mainly tidal streams from disrupted dwarf galaxies) around the Andromeda galaxy. The analysis of the data has showed that the FSQ+STL 11000 combination is an excellent equipment for exploring panoramic fields around nearby galaxies, providing results of scientific value.

With this objective, I planned a mosaic of two frames that with my equipment covered a field of 7º x 5º. During the year 2008 I spent a lot of nights on this project, acquiring a big quantity of luminance exposure. Altogether I have 13 hours of accumulated exposure on one of the frames and almost 12 on the other. I also took more than 100 short exposures (half minute or so) to get the necessary data to solve the core of the galaxy.

The luminance mosaic was composed with PixInsight, with its StarAlignment tool. This mosaic, in spite of only having two frames, it is a bit complicated to compose it well. In first place, because of the wide field extension and, secondly, because I planned a very small overlap area (7% only). PixInsight composed it very well, while other software packages produced both big field deformation and interpolation artifacts.

In the year 2009 I was able to took color exposures (6 hours in total), but this time with the galaxy in the center of the field (no time for mosaics that season!). With that new color information, I have composed this 2008-2009 LRGB image.

The final result, although is a very deep image, is not exactly the one that I expected. A critical view of the image shows several points that should be improved. For example:

- With the color addition in 2009, there is still a clear lack of chrominance to support the luminance. Although I increased the color saturation trying to improve this, the obtained colors did not satisfy me: for example, Hydrogen alpha regions show salmon-pink color instead of red.

- Some stars near the core show dark rings, as a result of a bad implementation (from my side) of the luminance deconvolution process.

Anyway, all this work has allowed me to learn really a lot both from the mistakes I made and from the experimentation with new processing techniques. Unfortunately, even knowing that some more exposure time with an Hydrogen alpha filter would improve the pink color, and reprocessing the image from the beginning would eliminate the dark rings, currently I have no time to do it. So, for the moment, I will leave the image like this. 

Guide & camera control: CCDSoft. Processing: PixInsight.

Please see more exposure details and a full resolution version of the picture in Gallery section.