M45: The Pleiades

Date: 27/01/08    Time: 2030hrs   Location: Sunningwell   Temperature: 5.6ºC  Relative Humidity: 76%

Camera: Nikon D80    Scope: William Optics Z66 Apo Doublet at prime focus   Mount: piggy-backed on Meade LX90 in equatorial mode  Exposures: 11x120 seconds  ISO: 1600   F ratio: 5.9   Guidance: Autoguided

Taken 9 months after my first attempt at M45 - the picture above illustrates the differences between a conventional camera zoom lens and an astronomical telescope.  Virtually no chromatic aberration in this picture and the superior light transmission of the William Optics lens (and of course a larger objective aperture) combine to make this picture sharper and more revealing of the nebulosity around Alcyone, Merope and Electra and Maia from which these main stars of the cluster formed, than in the previous picture.  Duration of each exposure was limited by the degree of light pollution, dark subtraction was carried out by the NR function of the camera itself as with M33 which doubled the length of time taken for each shot, and I lost one exposure to a satellite trail.  The 11 good frames were stacked with Maxim DL and the light pollution was subtracted with a blurred duplicate using Photoshop.  This is the result of a third trial and error midtone adjustment using the curves command in the individual RGB channels after black and white point setting, and the final image has some Gaussian blur (radius 1.2) applied and Noise Ninja filter with default settings.

 

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