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M31 - bludgeoned into submission!


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Getting through last years data at last.... :(

Had all sorts of problems with this - funny coloured galaxy and light pollution gradients....

Still not overly happy with this - but after soooo long processing I decided to call time and post this iteration before starting again from scratch! At least I have something to show for the struggle!


RGB One Shot Colour

24x 600sec light exposures

Flats(+Bias), Darks processed

Taken over two nights. The first 12 were respectable, the second not as good due to mist/high cloud closing in (can't remember which!) Used all of it anyway - a trade off I suppose between light pollution/detail/noise....

Tak FSQ106-ED @ native - 530mm/f.5

SBIG 4000XCM - OSC self guiding @ -20c

IDAS-V2 filter

Tak EM400 mount

Control via 17" G4 Apple Powerbook running MicroProjects Equinox 6 and Image.

Pre-processed, aligned and stacked in Nebulosity2.

Post Processing in PhotoShop CS3 + Noel's Actions +RC's GradientXT.

Anyway, enough excuses - here she is..... ********* !!!!

Thanks for looking,

Clear skies,



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I really do not know what more you want to do with your data, that's one of the best M31, I have ever seen, and I have seen a few...

By the way, seeing you own a color cam as well, can we trade technique? what do you do with your flats, do you convert them to color and then to monochrome before using them? or do you use them raw?


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Thanks guys for the kind feedback....

Serge, as for flats - I've had a few problems (as others will attest!)

I use an Electro-luminescent Panel fitted with 2 thickish sheets of perspex (clipped together with bulldog clips so I can add or remove white sheets of paper to give me around 5 second exposures depending on my f ratio - as I have both the Tak focal extender f8 and reducer f3.6).

I go for around 5 seconds (about 20,000 adu count) as when I was making them before at less than one second I could see (and measure) a darker area, that turned out to be the shutter shadow.... I think...

I was advised to use a 'boxcar filter' to destroy the bayer matrix data - but - working on a Mac I do not have that facility in Microprojects Equinox Image (the software that controls the camera) or Nebulosity 2 where I process the files.....

I got in touch with Darryl from Microprojects who suggested that I Median stacked the CFA (colour filter array) Flat files (after Bias subtracting them), and then convert that new CFA Master Flat File to a GreyScale Flat..... here's what he said:

"However, because a grey scale conversion does use the demosaic algo you do lose very fine corrections. For this reason you want to do as little conversion as possible. EI allows you to adjust the amount of processing a demosaic conversion does. The algo I use was designed by a math wizard friend of mine at MIT but in this case you don't want to use it! Adjust the Edge Processing slider all the way to the left. That does a straight demosaic without extending the kernal size and doing the magic that his algo does."

Once this is done I can run this flat through either Equinox Image or via Nebulosity 2 (as I quite like the new Image-Processing-Multiple Sets function. If in Nebulosity I also run a mild blur when it's doing its thing!

I'm not an expert, but it appears to work for me....

Hope this helps...!?

Regards and clear skies to you all,


Edited by TakMan
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Great stuff, Damian. Very strong data. I love that hot core and the way you have controlled it really close to the centre. That is not easy.

I was going to suggest you try Hasta La Vista Green, a freebie from Rogelio Bernal Andreo, but I remember it is non Mac. PixInsight has a tool for sorting green. I'll gladly buzz your image through it if you send me one. (I think there is a green imbalance in parts.)

My website is in my sig.


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Thanks for that offer Ollie - I will forward you a .tif file if that's OK....?

Being on a Mac does have it's disadvantages - although PixInsight IS Mac compatible... I've been cleared (budget wise) to upgrade the studio Macs April/May time, so when I have one of the new super 17" PowerBooks (3k's worth when fully upgraded!), then I might just have to treat myself to a copy of this PixInsight - I'll then be another looking to 'Harry's Pages'!!!!

Look out for a large file clogging up your inbox soon!



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Ollie kindly ran his PixInsight magic through it - the result is below....

Now it's looking too light again - I'm sure this is NOT Ollie's setting just how my Mac uploads it onto here...

Ollie if you'd also like to upload one for comparison that would be most useful....

Hopefully he can also add later exactly what function he ran in PixInsight to achieve this...?

Thanks for looking!



Edited by TakMan
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Sure, this is on my SmugMug site but that does change it from how it looks in Ps.

The Pi routines I ran were SCNR, Background neutralization and colour calibration but then I layered Damian's original galaxy onto the new background. There are a still a few green tinges but you could potter away to get them out. Green is the killer in AP in my view.



Edited by ollypenrice
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