M 45 

The “Pleiades”, M 45, aka “The Seven Sisters”, is an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of about 444 light years, it is among the nearest star clusters to Earth. The cluster is dominated by hot blue and luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars are now considered likely to be an unrelated dust cloud in the interstellar medium through which the stars are currently passing.

Open cluster M45 (Pleiades), 3 February 2014, Noordwijk, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 400 ISO, 129 s, stack of 3 frames (fitswork).

Open cluster M45 (Pleiades), 21 January 2017, Noordwijk, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 800 ISO, 400 sec, 20 frames each 20 sec (fitswork).

M45, Vorst (D), 30 Dec 2019, Canon EF 70-200 mm f/4 L USM telelens, Canon EOS 600D, UV-IR filter, 800 ISO, f = 200 mm,  stack of 15 exposures, each 30 sec, PixInsight

M 45 (Pleiades),  Noordwijk (NL), 21 January 2017, William Optics APO 110 mm FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 800 ISO, f = 770 mm,  400 sec, PixInsight V 1.8.8-5

During September 2021, I made some test runs with my new monochromatic CCD ASI1600mm pro. I used the L (luminance, UV-IR) filter, stacked 100 light frames (10 sec each). Unfortunately, no auto-guiding, but the individual exposures were sufficiently short. Bias, dark and flat frames were taken too. The ASI is, mainly due to its cooling, more sensitive than the Canon EOS, which can be seen comparing the Sep 2021 image with the previous ones.  Image processing was done using PixInsight V 1.8.8.-10.

M45, Plejades, 04 September 2021, Kempen, William Optics APO 110 mm, f/7, L (UV-IR) filter, ASI1600mm pro,

gain 139, T = -10C, 1000 sec (100 x 10 sec). No auto-guiding. Image processing with PixInsight

Inspired by the test image above (unguided and rather short exposure !) obtained in 2021 using my new ASI camera, I spent more time in November 2022 on M45, this time using all 4 broad-band filters L, R, G, B, also auto guiding was active.

M45, Plejades, 25 November 2022, Kempen (D), William Optics APO 110 mm, f/7, LRGB, ASI1600mm pro,

gain 139, T = -10C, 3600 sec (L), 2040 sec (R, G), 1920 sec (B). Image processing with PixInsight 1.8.9

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