M31 - First attempt

[Bob Andersson]

Hi folks,

We had an unprecedented sequence of clear nights here in the south of England last week during which I was able to have a first attempt at M31 (Wikipedia). This is also my first attempt at processing the data and, as usual, there are so many choices to make along the way that I'll flag this up as a preview so that I can revisit it later and reprocess as needed. I might even link to the full size 4096 x 4096 pixel image at that point but for starters here's a 1024 x 1024 pixel version:

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  'Scope: TEC 140
  Mount: ASA DDM60 Pro mount - an awesome bit of kit as even the 1,500 second subs were unguided!
  Camera: FLI ML16803
  Subs: 5 x 1,000 seconds using each of Astrodon Tru-Balance RGB filters plus 10 x 1,500 seconds using an Astrodon 3nm Ha filter
  Software: PixInsight and Photoshop CS6
  

The colour of the stars and the majority of the galaxy is muted. I could have pushed harder, and I might yet do so, but aesthetically I prefer to avoid a heavy hand. The Ha emission nebula was boosted so as to be visible and, of course, the brightness and contrast of the galaxy was to tweaked to show up structure.

The Ha processing went a little differently than I've been used too. Combining the 10 x 1,500 second subs produced an image with a fairly high contribution from the stars as well as from the emission nebulosity. Lacking a narrowband continuum filter I used PixInsight's PixelMath to subtract a portion (1/15th) of the Green signal from the Ha one using linear (unstretched) data. Green because my assumption is that that colour is pretty isolated from Ha and Hb emission, the proportion being chosen by trial and error to remove as much as possible of the Ha signal while not clipping any areas "below" black. That left me with a very much reduced core which was actually pretty distinctly separated from the spiral distribution of the emission nebulae. I still had to remove quite a number of stars, carefully avoiding removing small patches of nebulosity by doing a blink comparison with a "Stars Only" image derived from the RGB data but once that was done and the result tidied up and coloured I added the result to the RGB image.

Comments and criticism welcome.

Bob.

[astrostu]

Stunning image well done!

Sent from my HTC Desire HD A9191 using Tapatalk

[Gina]

That's brilliant - fantastic detail and colour I can't believe this is the first time you've done this - it's the work of an expert!

[alpal]

That's brilliant - fantastic detail and colour I can't believe this is the first time you've done this - it's the work of an expert!

I agree - an expert - well done.

[earth titan]

Blimey.

Difficult to see how you could improve on that one!!

[ultranova]

i am with Tom on that one

[Zendrix]

amazing work!!!

[paul schofield]

Best M31 I have seen. Well done.

[laser_jock99]

I can't believe this is the first time you've done this....

Nor me. It's very good though!

[Quatermass]

Fantastic job

Sent from my GT-S5670 using Tapatalk 2

[farunj]

That's stunning!! Wow!!

[Folkert]

How can this be a "first attempt"? This is in my eyes a fabulous picture, I will refuse to share my first attempts after this! Feeling embarrassed! No, this is great, thanks for sharing!

[Bob Andersson]

Hi folks,

Thanks for the kind words. Yes, it really is my first attempt but I am more than pleased with it. I guess the trouble is that I've seen all the imperfections as I processed the data and think "could do better", especially if I am to eventually produce a full resolution version for public consumption.

But, hand wringing aside, what I love about images such as this is the sense of scale. Something the size of our own North America nebula, at about 100 light years across, would be pretty insignificant in the image above and the compression waves marked out by the spiral structure of Ha emission are, for me, like a beating heart pumping out fesh bursts of star formation and the consequent enrichment of the interstellar environment of the very stuff of life.

Bob.

[dmahon]

'Scope: TEC 140

Mount: ASA DDM60 Pro mount - an awesome bit of kit as even the 1,500 second subs were unguided!

Camera: FLI ML16803

Subs: 5 x 1,000 seconds using each of Astrodon Tru-Balance RGB filters plus 10 x 1,500 seconds using an Astrodon 3nm Ha filter

Software: PixInsight and Photoshop CS6

• 
  

That's brilliant - fantastic detail and colour I can't believe this is the first time you've done this - it's the work of an expert!

I take it you meant first attempt at processing THIS data, as it's obviously not your first attempt at processing (it would be a very unusual list of equipment for someone first starting out).

EDIT: PS - it is very good.

[Shibby]

That's a treat of an image, milky smooth! I have to assume you are a reasonably experienced imager, but regardless of that or not it's a corker

[Bob Andersson]

Hi dmahon,

It's my first attempt at capturing M31 on any camera and my first run at processing the data. I've posted a number of images but I still am pretty near the bottom of the learning curve as I've had my TEC 140 for only a few months. The mount and camera has been in use for less than a year and prior to that I made do with a DSLR and a cheap (think $200) motorised mount. But my interest in astronomy stretches back over more than four decades and it was only the opportunity to spend a working career bumming my way around the world from one five star hotel to another (airline pilot) that stopped me following a career in astronomy/astrophysics. Now that I'm retired I've finally got around to spending serious time, and money, on other pursuits!

Glad you liked the result.

Hi Shibby,

I've been fooling around with Photoshop for a few years now, partly with DSLR astrophotography but mostly with terrestrial. Processing astronomical images does take its use to a whole 'nother level and that's not counting the extreme learning curve that a program like PixInsight requires. Good fun, though.

Bob.

[Zul]

Beautiful!

[MarkMayf]

That's amazing!

[SkyJamie]

Awesome image Bob!

Jamie

[Spikey]

That's an interesting rendition Bob, you've handled the Ha very well. Out of interest in the combination method I'd quite like to see the RGB & Ha images individually if possible.

[Bob Andersson]

Hi Simon,

Not sure if this is exactly what you are after but I've put together some of the components:

• 

The monochrome "R + G + B, Stars Removed" image is showing a more extended disk than the image that kicked off this thread and more structure is visible although I think that is partly due to the lack of stars which can be distracting. That gives me hope that there's still room for improvement in the final image but getting the balance between maximising the information content, for want of a better phrase, and getting the aesthetics right is a trick I'm still learning!
Maybe some more processing notes are in order. I don't shoot luminance subs so I have yet to experiment with binning. I combine all my R, G and B subs to produce both a luminance image and a separate, and inevitably less deep, colour image. Apart from white balance and saturation tweaks that colour image is pretty much left alone and used as a "Color" layer in Photoshop. The luminance image for this shot was processed in PixInsight in a standard way with the extra step of creating a Star Mask to allow a spot of "HDRMultiscaleProcessing". The result was exported to Photoshop (16 bit TIFF is my preferred route) and then the stars were removed by a sequence of Dust & Scratches filter applications followed by a painstaking manual cleanup. I then subtracted the "No Stars" version from the original to produce a "Just Stars" version. The "Just Stars" version went back through PixInsight for a spot of deconvolution but I ended up applying virtually none as there weren't any bloated stars in this image. I often pass a "No Stars" image back through PixInsight as well but this time I saw no benefit and achieved a better result by using a combination of the "Astronomy Tools" contrast enhancement "Action" and Topaz Labs "InFocus" Photoshop plug-in to boost the micro-contrast.
The star removal process was key to getting the Ha image into a usable form. As you can see, subtracting the "Green divided by 15" signal from the stacked Ha image got rid of a lot of the unwanted continuum signal in the disk but I was left with quite a number of star ghosts, presumably from red supergiants local to our own galaxy. With those removed (I used a blink comparison method by toggling a temporarily added "Just Stars" layer - see the previous paragraph) you can see the result above. There is still quite an excess of an Ha signal from the central bulge. I could have just erased it but as it shows spiral structure I decided to leave it and, fortunately, my colour choice for the Ha component didn't upset the overall colour balance of the core when I added the Ha data as a Photoshop screen layer.
The bottom right image is just a version of the originally posted image but without the Ha layer.
Update: As I see this post is now at the top of page two I'll add a copy of the original image that started this thread to allow easier comparison with the components in the image above:

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Bob.

[Spikey]

Thanks for taking the time to write that up Bob. I was interested in seeing how you had cleaned up the Ha to add to the image as it's really complimented the result.

As Andromeda is coming round nicely for me at the moment I'm planning how to attempt this with a small chip CCD (mosaic) rather than a DSLR.

[x6gas]

Nor me. It's very good though!

+1 That's amazing.

[Ewan]

Makes my first DSO look like my child drew it with crayons , looks absolutly stunning but you do realise when the FBI finds out you nicked Hubble your in deep mate !!!

I dare say your kits not cheap & you get what you pay for, an amazing shot, makes me a feel a little inadequate about my next posted topic of my subs

Please up the full image if possible as i'm sure even with any imperfections it will look breathtaking.

All the best Bob & keep em coming please

[Bob Andersson]

Hi Ewan,

Well, as an "Old Hastonian" (ex Hastings Grammar School boy) how can I refuse you. Actually I will a little bit as I'm only happy sharing a 2048 x 2048 pixel version as I think the extra detail available at 4096 x 4096 is minimal because of noise introduced much earlier in processing. Maybe something to return to when I have more time.

Bob.