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M45, The Pleiades | by Terry Hancock
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M45, The Pleiades

M45, The Pleiades in natural color, with luminance and RGB combined. For the color I used 10 minute and shorter 5 minute exposures together with the luminance to help prevent the very hot blue stars from becoming bloated.


Total Exposure time 4.75 hours


Clear Skies


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Date of Shoot 13th and 16th October 2012

All exposures unbinned

Luminance 16 x 5 min, 15 x 1 min

RGB 6 x 10 min ea, 7 x 5 min ea.

QHY9M monochrome CCD cooled to -30C

Thomas M. Back TMB 92SS F5.5 APO Refractor

Paramount GT-1100S German Equatorial Mount (with MKS 4000)

Image Aquisition Maxim DL

Stacking and Calibrating: CCDStack

Registration of images in Registar

Post Processing Photoshop CS5


Among the closest star clusters is M45, colloquially known as the "Seven Sisters". Due to its close proximity (a mere 440 light-years), and population of extremely hot and luminous stars, it can be easily seen with the naked eye near the constellation of Taurus. The number of visible stars in this open cluster can quickly tell an astronomer how dark a location is on a night of observation. Up to fourteen of the more than one thousand stars in M45 can be seen with the unaided eye.


The bright blue clouds surrounding the stars forms a reflection nebula known as the Maia Nebula. The enormous cloud of dust reflects the light from the hot young stars and was once assumed to be the remnants of the young stars' births, but is now known to be the serendipitous interaction of an unrelated dusty region being illuminated by the open cluster of stars passing through its interstellar neighborhood. Look closely and you will see the faint brown clouds of dusty material surrounding the cluster.


For comparison here is my earlier shoot from 2 years ago using a Canon 5D II DSLR together with the TMB 130SS

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Taken on October 18, 2012