The Andromeda Galaxy – Oct DSC

[JonH]

This is not the final image, I am just after everyone's opinion about the colour balance and such as without a calibrated monitor I pretty much guessing!
There is still a lot of work to be done with this and i think there is still a fair amount of data to be brought out, but it shows that I have captured detail almost right to the core which is exactly what I wanted!
Had I not lost the 10sec subs the core might be better!

90x300sec
20x150sec
16x30sec
All stacked and processed in Iris with a little final tweaking in photoshop.
The different length subs were stacked and combined in Iris using the desc_hdr merge_hdr and reduce_hdr1 commands. Not very easy to figure out but when you get it right it does a pretty good job! I still think a full re-stack might be in order to really utilise these commands though.



Full size (this is still a heavily compressed JPEG, just bigger!):
http://farm9.staticflickr.com/8473/8097434821_87fec7a005_k.jpg

[MarkS]

Looking pretty good!!

I would say the colour is more or less right - just some minor tweaking required.  You've coped well with the huge dynamic range.  The core brightness is fairly well controlled and you have good star colours.  But you have a strange artifact around the edge of the galaxy - some kind of posterisation - visible steps in colour and brightness - you should check which stage in the processing introduced this.

Looking forward to the next version ...

Mark

[JonH]

Yes I noticed posterization, it appeared funnily enough while trying to tame the blue. Even before I had started to stretch the colours I had an abundance of blue stars, and no matter what I tried it only got worse.
I eventually managed to get it under control in the stars, but it created that as a side effect. Is very noticeable in the blue along the right!
Also in the smaller M110 there is something very odd going on where it appears all the colour to the central part has been lost then suddenly appears again at a very defined point.
I'm not 100% sure when this happened as I was paying so much attention to getting everything right but I have an idea why it happened.

[Carole]

That's pretty amazing considering how long ago you started imaging.  The core looks very good to me, and the detail in the galaxy, I think you've tried to darken the sky colour too much and I wonder whether this is contributing to the artefact problem. 

Excellent work.

Carole

[Mike]

Very nice Jon and especially for a newcomer.

Please don't forget to put your details re: Scope, Camera, Mount, etc.

Thanks. Mike

[JonH]

Thanks

Yes good point:
Equinox ED80 with 0.85 flattener/reducer (spacing yet to be set correctly)
NEQ6 with eqmod
Modified Canon 450D
Guiding with QHY5 on ST80
Captured with APT

[JohnP]

Blimey Jon,

That is excellent even more so seeing how short you have been imaging. Like Mark says a few weird things going on around edges (look very purple). The focus & alignment is excellent. To compare this was my first ever attempt at it...

http://jpastronomy.co.uk/graphics/archive%20images/dso/galaxy/m31_007.html

Keep up the good start & you'll be giving Mark a run for his money in no time.

John.

[MarkS]

I forgot to mention that your star shapes are pretty good right out to the corners.  There are no obvious distortions.  This tells me your reducer/flattener is pretty well matched to the optics of the Equinox ED80.  Especially since a DSLR has such a large chip size.

[JonH]

Thanks John, it's getting there!

Keep up the good start & you'll be giving Mark a run for his money in no time.

I dunno about that, the difference between mine and Mark's images even before the processing is finished is huge!
That said I'm pretty happy with the results I'm getting so far.

I'm very happy with the star shapes in this, it's the best I have had to date by a long shot!
What's weird is the stars are better than in any individual sub?
I was wondering if by using the quadratic global matching in Iris with so much data it has actually 'fixed' them for me?

[MarkS]

What's weird is the stars are better than in any individual sub?
I was wondering if by using the quadratic global matching in Iris with so much data it has actually 'fixed' them for me?

It's not weird at all. Star shapes in a single sub are messed up by the CFA (colour filter array or Bayer matrix) over the sensor's pixels and the subsequent pixel interpolation that is performed during the construction of the colour image from the raw data.  When many subs are added together, especially when dithering was used during acquisition, these effects are averaged out.  It's one of the important reasons we use dithering

[Ivor]

Good image Jon, I'm looking forward to the final result with the suggested changes above..

[RobertM]

Great image Jon, you're really coming on leaps and bounds

To be critical I would say that the background is a bit clipped and because of that you've lost a lot of background data but the rest is looking really good.  I also think HDR should give more core detail than you have.  I've found M31 to be a bit of a pig to colour balance in the past but that's a pretty good version as seen with this crumby monitor.  If you can sort the background out then the rest should be much easier.

Robert

[The Thing]

Good job Jon!

I haven't got round to my measly 9x300s subs yet and looking at this I am bound to be disappointed with the result..

[JonH]

Yes I agree about the background, it was done deliberately as I was loosing patients trying to get rid of the gradients. In the end I just gave up and darkened it until they couldn't be seen anymore.
In hindsight this was a stupid move as lost a lot of fainter stars and fainter detail to the outer edges.

[JonH]

Thanks Duncan
To be honest you unless you're up for a huge challenge, spending hours on end processing and even more time waiting for your computer to register and stack, 9 subs is the way to go!
You can only work with what you've got...