Pleiades aka The Seven Sisters/Subaru/Cr42/M45/Mel22 (c)

[ramdom]

Total integration: 240m/4h (90 x 120s + 240 x 15s).

Camera: QH247C (24mp OSC) CMOS cooled to -15 degrees C.

Telescope: Takahashi FC100DF Steinheil fluorite doublet apochromat refractor @ f/4.9.

Reducer: Takahashi FC-35 2".

Mount: Paramount MyT.

Filters: 2" Baader UV-IR-Cut.

Software: TheSkyX Pro, Sharpcap, PixInsight.

 

Inline image is uploaded to the forum. Full sized image is here: http://ram.org/images/space/scope/1.7.4.6/m45_c_90x120s+240x15s_240m.jpg

The Pleiades (M45) is an open star cluster and corresponding reflection nebulae in the constellation Taurus. It is the first astronomical object I recall in my memory: I remember looking at it through a small courtyard from our first floor home when I was a child---it sparked my fascination with science and astronomy and getting to know the night sky, as well as the associated mythologies different human cultures have created around these objects. The Pleiades was the easiest object to remember, not only due to its brightness but also its distinctive twinkle and the challenge of distinguishing the stars within it.

The nine brightest stars in the Pleiades cluster are named after the Seven Sisters in Greek mythology, along with their parents: Alcyone, Atlas (father), Electra, Maia, Merope, Taygeta, Pleione (mother), Celaeno, and Sterope/Asterope. The cluster however contains more than one thousand confirmed members, fourteen of which can apparently be distinguished by the naked eye. Unlike the typical emission nebula I image, all the light is due to reflection of blue light from the hot young stars on the dust in the interstellar medium - there is no ionising radiation and therefore it is not a narrowband composition but reflects largely what the sensor has captured. The Merope and Maia nebulae are the major ones in this star cluster.

The dust responsible for the nebulosity is not uniformly distributed, and is concentrated in two layers. These layers may have been formed by deceleration due to radiation pressure as the dust has moved towards the stars, making them appear as though waves of hair are flowing the stars and giving us a sight to behold through powerful telescopes or ordinary imaging equipment. If you look closely you can see the waviness of the dust lanes observable to the very edges of the blue nebulae.

The 110 million year old cluster is about eight light years across and about 136 parsecs away, making it one of the nearest star clusters to us. It is expected to disperse within the next 250 million years.

Here are a couple of other processing attempts, so you can see that no matter what I do, the overall result looks very similar. The second used a very different processing pathway, which brings out the blues more and the last one is a version with less data but also sharper/smaller stars.  But I like my final version above since it brings out some of the dust lanes (which the first image below does as well) and also shows how much further out the reflection nebulae extend.

https://www.astrobin.com/421142/B/   https://www.astrobin.com/421142/C/

I was going to keep collecting data on this but for now decided to focus on other targets if the sky clears up since it's full moon out and I think this camera works best when it is fully dark out and I want to swap the cameras between my two scopes to do something different.

As always, thanks for looking!

--Ram

 

[Starwiz]

Nice image with very round stars. 

It darkens considerably towards the edges.  Did you use flats?

John

[ramdom]

Thanks!

Not in these final compositions. When I first did the 240 x 15s stack, I tried it with and without flats and didn't make much of a difference (either that or I still don't know how to do flats properly - I can get rid of the smudges, etc. if they are present but I've never been able to cure gradients with flats). There is some vignetting but it is at the very tip of the corners.   The fall off is due to me being very aggressive with the curves...

--Ram

 

[Starwiz]

1 minute ago, ramdom said:

Thanks!

Not in these final compositions. When I first did the 240 x 15s stack, I tried it with and without flats and didn't make much of a difference (either that or I still don't know how to do flats properly - I can get rid of the smudges, etc. if they are present but I've never been able to cure gradients with flats). There is some vignetting but it is at the very tip of the corners.   The fall off is due to me being very aggressive with the curves...

--Ram

 

If you do use flats, you should include dark flats too.  I've found flats quite a challenge to get right, but when they are good it really makes a difference.

John