Tuesday, December 19, 2023

The Collinder 65 star cluster

 Collinder 65 (Cr 65) is a wide (about 3.7°) star cluster in Taurus midway between the constellations Orion and Auriga.  It was catalogued by the Swedish astronomer Per Collinder in 1931.  It is not very well known but is easily recognized with binoculars.

The location of Collinder 65 is marked by the red circle. Chart credit: IAU (Creative Commons Attribution 4.0 International license)


Collinder 65 is marked with the white circle.  Sony A7iii + Rokinon 35mm f/1.8 + softon filter.  ISO 1600, 30 s.

A closer look.  E-M1iii + 75mm f/1.8 + softon filter.  ISO 1600, 60 s.

The yellowish star near the center in this image is 119 Tauri, a red supergiant.  The brighter star to the left of center is magnitude-3 Zeta Tauri, and just above that is the Crab Nebula, M1.  Here is a zoomed-in view:

The Crab Nebula, Messier 1, is the small blob in the center of this 3°-wide image.

Here is a closer view of Collinder 65:

E-P5 + Rokinon 135mm f/2 + Kase AstroBlast filter.  ISO 1600, 30s.

In this image 119 Tauri has a cyan or teal hue.  This is a consequence of the photographic color-balance processing used to mitigate red airglow.  There are no green-hued stars in nature.   A similar color-shift is evident in this image of the Hyades cluster:

E-M1iii + Olympus 75mm f/1.8 + softon filter.  ISO 1600, 30 s.

The brightest star in this image is Aldebaran, a magnitude-0.9 orange giant.  Aldebaran is not a physical member of the Hyades cluster - it is a foreground object at roughly half the distance (67 ly).

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