M 3
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).
Technical data
Optic GSO RC12 Truss - Aperture 304mm, focal lenght 2432mm, f/8
Mount 10Micron GM2000 HPSII
Camera ZWO ASI 2600 MM Pro with filter wheel 7 positions
Filters Astrodon Gen2 E-Serie Tru-Balance 50mm unmounted RGB
Guiding system ZWO OAG-L with guide camera ASI 174MM
Exposure details R 98x30" bin2 -15C gain 100
G 97x30" bin2 -15C gain 100
B 99x30" bin2 -15C gain 100
Total integration 2h27'
Acquisition Voyager, PHD2
Processing Pixinsight 1.8, Photoshop CS5, BlurXTerminato, NoiseXTerminator, StarXTerminator
SQM-L 20.40
Location Promiod (Aosta Valley, Italy), own remote observatory
Date 26 February 2026
© Roberto Marinoni 2019 - All rights reserved