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Bob Andersson

The Pleiades

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Hi folks,

The Pleiades were the subject I chose for "first light" when I got my imaging system up and running earlier in the year. I promised myself I would return to them in the autumn and here's the result, uncropped apart from a 48 pixel wide border but then downsized by a factor of four:

Pleiades_v1.1_Web.jpg
  • The Pleiades

I've linked to a larger (2048 x 2048 pixel) version which you can see by clicking the image. The 4096 x 4096 pixel original doesn't really add anything to the party in terms of extra resolution of the nebulosity. The subs used were 5 x 1,000 seconds blue and 5 x 200 seconds in each of red, green and blue using my Astrodon Tru-Image filters. As ever the 'scope was my TEC 140 and the camera an ML16803.

Processing was a real challenge for me because the brightest stars were still well blown even on the 200 second subs. In the end I decided to do without any shorter exposures so I combined the 200 second RGB subs to get a colour image and combined the 200 and 1000 second blue subs using PI's HDRComposition tool to get a much deeper image of the reflection nebulosity while still controlling the size of the brightest stars. That image then had its stars removed and that's where the fun started as there was no way I could reliably clone out the brightest stars as they were so intimately bound with the illumination of the surrounding gas and dust. In the end I opted just to darken the very brightest stars as the whole purpose of the exercise was to try and prevent ringing during subsequent processing of the nebulosity and ringing is basically triggered by very sharp transitions in brightness. Anyway, the "no stars" image went back from Photoshop into PI where the tool of choice was LocalHistogramEqualisation. The original plus the LHE version were both processed further in Photoshop and then blended together and the result coloured using a Curves layer. The cleaned up and enhanced RGB image was then added as a screen layer which neatly added the stars back, including over-painting those problematic very bright ones, and also slightly modified the colours of part of the brightest areas of the nebulosity. Obviously there were lots of extra tweaks along the way but those were the headline steps.

Quite an adventure and there's always a worry that the end result owes too much to the choices during post rather than reflecting (sic) what was actually there but I'm pleased with the result, especially as I wasn't expecting to see so much structure so distant from the Pleiades themselves. I hope you like the result.

Bob.

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Another stunner Bob.

Such depth and detail. Can't wait until I can delve into CCD imaging.

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That is truly stunning. I find it fascinating to see so much detail in this photo - it's almost a textbook example of how different an astrophoto can look compared to the view through an eyepiece.

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Stunning nebulosity Bob!

You may consider controlling the stars form as they are a bit affected by LHE. May be mask with a PI star mask

Mark

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Wow, that's a fantastic image excellently processed... Lots of really nice structure. Interesting exposure choice to enhance the blue components of the image. Was this your idea or something that you have read / seen else where?

Id have gone with a classic LRGB but iM now wondering how it would compare?

Food for thought! Great result.

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Hi folks,

I've been away for a few days (Las Vegas and the Grand Canyon) so it was really nice to come back and find so many positive comments.

@Mark72 Actually the vast majority of the stars weren't actually present in the image that had been LHE'ed as they had been cloned out but it proved impossible to clone out the very brightest stars given my choice of 200 seconds as the shortest exposure time. I think with hindsight that some shorter subs may have helped as well so maybe I'll return to this subject as time permits.

@Neil The exposure choices were entirely my own. I guess technical accuracy would demand a set of 1,000 second subs in red and green as well as blue but I don't believe they would have produced a useful signal in the very faintest regions despite the undoubted fact that there would be red and green components in those areas. So, laziness won out and I just opted for the long exposures using the blue filter.

Again folks, thanks for the feedback. I was genuinely surprised by how much nebulosity I found with what were quite a modest selection of subs. I was perilously close to the noise background of the sensor in trying to emphasise that detail and I think there is no way that I could have extracted that detail using anything other than a cooled monochrome CCD. That said, I confess to being a bit surprised that so few images out in the wild show the faint stuff. I genuinely don't believe I did anything extraordinary during post and while my Cotswold site is reasonably far from city lighting I do live in a large village so my skies aren't the darkest. Hopefully the image above will inspire more experienced folk than myself to revisit an old favourite and raise the bar even further as this has to be one of the most beautiful objects in the sky.

Bob.

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Fabulous image, I am stunned by the high amount of nebulosity in this image. Love the contrast between that and the darkness of space.

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Terrific piece of Imaging and Processing Bob.

M45 is a most attractive subject for an Imager, and an Observer.

Lots of the blue reflection material in your image typical of the Pleiades clusters Stellar birthplace.

Lovely sight Indeed.

You should submit this for APOD selection. If SGL were still running "Picture Of The Week"

I've no doubt the judges would have selected this baby :smiley:.

Well Done :icon_salut: .

Ron.

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wow, that really shows what the pleiades is like, as with my 130P i just see the few stars around, looking forward to getting some filters soon :) brilliant pic though :)

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I can't recall seeing a pleiades image as good as this one. Amazing colour and detail.

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Quite an image- the problem with shooting and processing the Pleiades is the bright stars in the cluster and their tendancy to bloom outwards. Having top quality optics like your TEC scope must help a lot though?

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Good dark sites help the S/N problem and prevent gradients! They don't bring you anymore signal but the signal you get is of a higher quality so you don't need to work as hard! A couple of weeks ago I was fortunate enough to speed a long weekend in the Wye valley, with friends, the sky was superb when it was clear.

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Not bad.... Not bad at all... :grin: I agree with Ron - This is very much worthy of submission to APOD :hello2: .

I have the same filters, but am still trying to get to grips with the concept of LRGB imaging - I simply can't wrap my head around how saturated images (as the stars surely must be, even at 300s unbinned) can produce colour images as beautiful as this... but obviously they can (and do!). Simply awesome, and thanks very much for setting a level to aspire to...

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I hope you've sent this off to every astro mag and competition in the land - next to some of the wide field work of Greg Parker, planetary work of Ian Sharp and the dso's of Peter Shah this has joined the top of the list in my favourites catalogue - very well done. :smiley:

David

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certainly the best m45 image ive yet seen....superb! im even gonna print-up your write up as inspiration in a learning file!

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Great, detailed image! I think your processing technique for the fainter bits may have lost you some of the colour balance, leaving it very blue, but it's a nice image!

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