M45 Pleiades, a beautiful sight

Well during most of the recent clear nights I’ve been working on imaging M31 via different setups (see other posts) but late last night the Pleiades were comfortably above the mountain horizon and so I decided to take a shot at capturing this beautiful open cluster. I’d been imaging with the Canon 100-400 L IS on my 20D, so that was what I continued to use – probably my choice for M45 anyway.

Maybe nearly 2am isn’t the ideal time to start such a project (if you want to sleep) but there we go. The mountain weather decided to play games with me, clouds rolling in and out  and having decided upon ISO 800 as a compromise to allow finer detail to show through I knew that I needed a minimum of about 1 1/2 hours exposure. I was still collecting data as dawn arrived; after sorting through everything I decided upon the 43 best subs, giving me almost my desired exposure time. In the clear moments conditions were as follows: Light breeze, Transparency Average to Good, Seeing Fair. You can always look at my weather station to get more general weather details. Here’s the processed image:

m45-110907-b3-3framed  Click image for a larger view …

(update) – During October I had the opportunity to re-image M45. On this occasion I made a much deeper exposure using ISO1600 for nearly four & a half hours of exposure – this allowed for a different processing and shows significantly more nebulosity whilst controlling the stars. Note how the nebulosity below Merope is not as intensely blue as the other nebulosity; there has been suggestion that this layer of dust has fewer hot blue stars in its vicinity, hence the change in hue. I prefer the long exposure image, you can see it below …

m45-awstack85-wb-asinh-ps-1  Click image for a larger view

The Pleiades or Messier 45 have been known since ancient times, with clear references to them in ancient Greek literature. They go under various names in different cultures around the world:

  • Messier 45
  • Pleiades
  • Severn Sisters
  • Subaru
  • Matariki
  • Also bees, hens and probably a few more too! I’m sure the Wiki article will list many more.

The image below is my usual Messier information board, click it to see a larger version:

M45 Sept07

The standout feature of this cluster is its nebulosity. It is a reflection nebula; a dust cloud, that is unrelated to the star cluster, is reflecting light from the cluster’s hot blue stars. This can be seen when carefully viewed through reasonable equipment but it really shows itself in long exposure photographs.

As I’ve mentioned already, the cluster is sometimes called the ‘Severn Sisters’, this name is derived from Greek Mythology where Atlas & Pleione had seven daughters, the bright stars of this open cluster are named after this family as labeled in the image below.

M45 The Pleiades  Click to see the larger version

All in all definitely a sight worth seeing; and photographing.


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