About image

Globular cluster M3 is visible in the northern constellation Canes Venatici (The Hunting Dogs). It is formed by about 500,000 stars and has a distance of about 33,900 light years from the Earth: its apparent magnitude of 6.2 makes it visible to the naked eye under a dark sky. In this image, individual stars are difficult to distinguished in the densely packed core, but colors are apparent for the bright stars on the cluster's outskirts. M3’s many cool "red" giant stars take on a yellowish cast, while hotter giants and pulsating variable stars look light blue (text adapted from APOD). 

This image was taken from my home terrace with a very heavy light pollution all around.

Technical data
Optic       Tecnosky Apo refractor LT 130-910mm f/7
Mount       Skywatcher EQ8
Camera                      Atik 4000 with Starlight Xpress external filter wheel 5 positions
Filters                         Hutech Idas LPS P2 50mm unmounted, Baader 50mm unmounted RGB 
Guiding system         Artesky Ultraguide 70mm 
Exposure details    L 25x300" + 12x60" bin1 -15C

         R 27x120" bin1 -15C

         G 28x120" bin1 -15C
            B 29x120" bin1 -15C
Total integration       5.1h
Acquisition                Voyager, PHD2
Processing                Pixinsight 1.8, Photoshop CS5
SQM-L                       18.43    
Location                    Rescaldina (Italy), home terrace
Date                          16/17/18 March 2020