The Andromeda Galaxy – Oct DSC

[JonH]

I am slowly coming to some conclusions here, either Iris is not cut out for HDR images or I lack the ability to get it to!
To be honest it is more likely the latter 

Either way no matter what I try I only get so far before hitting a dead end! 
Think I might have to scrap the merge_hdr idea as it just isn't giving the results it should, for me at least!

[MarkS]

Iris is not really cut out for HDR images.  It's native representation is only 16bit integers/channel.  I've never really played with HDR in Iris because the first thing it forces you to do is to downsample back down to 16bit again.

[JonH]

Well at least I know it's not all me then...
I suppose that means I need to stick to using Iris for more basic processing and stacking then, and find a new bit of software to learn!
Any suggestions? The free'er the better!

[JonH]

And here we have process number two!
Yes I know the colour balance it miles out, but for this one I concentrated more and finding all the detail there was rather than messing about for ages trying to get the colours just right....
There is still much work to be done, but I have some really good ideas how I can improve this further, number one being to take more shorter subs and across of a wider range of exposures.
Either way I think I finally might have found a way to create a half decent HDR image! 



Larger version:
http://farm9.staticflickr.com/8047/8101210417_b19cefb6b3_k.jpg

[MarkS]

That's beginning to look very good! The colours within the galaxy and the star colours are great and it really is a stunning image for someone who has just started astrophotography.

It also clearly demonstrates the value of taking hours and hours of exposures in the battle against light pollution.  

Well done.  You ought to be really proud of it.

Mark

P.S. now you've just got to sort out that posterisation

[JonH]

Thanks Mark, It's finally getting somewhere close to what I am after!
I found there was a way of getting photoshop to create a HDR image at 32bit so until I get more powerful software I think that is the way to go.
This was only my first try at doing it this way and I think with some very careful manipulation I can get a touch more detail in the core, but I'm pretty sure I have found the outer extents now.
I'm really not liking uploading the jpeg's as it just trashes the data! I need to get me some server space somewhere to upload full size Tiff's, this one was over 140mb!
But if you could see the original those three little stars right in the core are visible!

I also want to get MORE exposure time on this! 

[Fay]

you really have done well Jon, background a little too dark and second version better than the first, great M31 even if you had been doing it for a few years!!!!!

[MarkS]

Photoshop is a good idea for HDR.

If you create a blurred version as a new layer e.g. a 5 pixel Gaussian blur and subtract say 50% of it from the original you will increase contrast in the dark lanes.  Try it in the brighter core areas but you might have to first mask the stars to prevent dark rings appearing round them after subtraction.  Don't sjk me for more details because I'm not a PS user.

Please don't bother uploading a 140Mb file - no-one will ever download it!  Just reduce the amount of compression you use on your JPG.

[JonH]

I might have to try this, the problem with PS though is although it will create a 32bit image from my three stacks it will let you do very little with it!
Although i do wonder if 32bit is enough to capture the full range? If i have three stacks each at 16bit then surely the final image would have to be 48bit to truly preserve everything?

[JonH]

I'd like to say this was process number three, but it's not, perhaps 300! But it is one that i am happy enough to post up.
86 x 5min subs stacked in Iris then processed in ImageJ with some final adjusting in Photoshop.

You might be interested to know that i haven't used any shorter subs in this at all, only the 5min ones!
I have spent a lot of time exploring out how to compress the dynamic range and still preserve the fainter detail and it looks like it is finally starting to pay off.

I'm not really sure if this is better or worse that my other tries with regard to colour, but it's making progress, i think....



Bigger one:
http://farm9.staticflickr.com/8057/8168177469_6f3696fea7_k.jpg

[Carole]

That's pretty stunning Jon, people who have been imaging for a few years would be well chuffed with that.  I prefer your version of 18th October as there is better colour.

Carole

[MarkS]

It's looking much better now!

[JonH]

Thanks, I'm pretty sure I managed to find all the usefull detail I can but Carole is right, more work it still needed on the colours.
I'm starting to wonder if I'll ever get the right! 

[Fay]

I like bits of the first one & bits of the second. bit more lane detail & contrast in the first, but both very nice

[RobertM]

Looking good but I agree with Fay.  You've lost contrast and perhaps pushed the processing a little far (though I can see what you were aiming for).  There is also now a very noticable gradient  from top left to bottom right.

As you can probably see, this processing malarky can just go on and on as there is nearly always something that can be improved

Robert