The Andromeda Galaxy, also classified as M31 in the Messier Catalog, is a spiral galaxy that is approximately 2.538 million light years from Earth in the direction of the Andromeda constellation, from which it takes its name.
It is the closest large galaxy to ours, the Milky Way; it is also visible to the naked eye and is among the most distant objects visible without the aid of instruments as long as you observe from a sufficiently dark place. M31 has a diameter that is about twice the size of our Milky Way (220000 light years against 100000).
The red specks visible along the spiral arms are called HII regions, which means they are emission nebulae associated with young stars.
Technical data Optic TS Optics 76 EDPH - Aperture 76mm, focal lenght 342mm, f/4.5 Mount Skywatcher EQ6R Camera ZWO ASI 294MM Pro with external filter wheel 7 positions Filters Antlia 36mm LRGB, Antlia 36mm Ha 3.5nm Guiding system Artesky Ultraguide 32mm Exposure details L 70x120" bin2 -15C
R 40x120" bin2 -15C G 40x120" bin2 -15C B 40x120" bin2 -15C
Ha 20x300" bin2 -15C
Gain 120, offset 30 Total integration 8h Acquisition Voyager, PHD2 Processing Pixinsight 1.8, Photoshop CS5 SQM-L 21.14 Location Promiod (Aosta Valley, Italy) Date 11 August, 5/6/7 November 2021