About image

The Pleiades (also known as the Seven Sisters or with the initials M45 in the Messier catalog) are an open cluster visible in the constellation of Taurus. 

This cluster has an apparent extension in the sky equal to about 4 times the full moon and is visible to the naked eye even from a moderately dark sky, where four / five stars can be counted, which rise to ten if viewed from a darker sky. 

In reality, the cluster has at least a hundred stars, visible only with long photographic exposures. 

The Pleiades are 440 light years away and are a young open cluster, with an estimated age of about 100 million years and an expected life of only another 250 million years. 

The stars are surrounded by a blue nebula: this type of nebula is called a reflection nebula and appears bright due to the reflection of the light of a bright and hot star by the dust present in the nebula. 

The cluster and the nebula are not physically linked (having different radial velocities): it therefore appears that the cluster is passing through a particularly dusty region of interstellar medium.

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 RGB
Guiding system    Artesky Ultraguide 32mm
Exposure details    L 85x180" bin2 -25C 

          R 24x180" -25C + 16x180" -15C, all bin2
                                    G 24x180" -25C + 16x180" -15C, all bin2
                                    B 24x180" -25C + 16x180" -15C, all bin2

          Gain 120, offset 30 

Total integration  10h15'
Acquisition      Voyager, PHD2
Processing      Pixinsight 1.8, Photoshop CS5, StarXTerminator, Topaz DenoiseAI
SQM-L       21.2    
Location       Promiod (Aosta Valley, Italy)
Date           5/6/7 November 2021