Makarian's Chain - Half Finished

[MarkS]

Not a lot of colour there are you going to shoot shorter subs for the colour?

I wasn't aware Markarian's Chain had much colour.  I could try increasing saturation I suppose.

Mark

[MarkS]

I didn't take any further subs last night because I have work in the morning and I needed to pack my equipment for France.

I have 130 x 5min subs but they are putting up a stong fight against being processed!

A straight sum of the subs leaves remnants of hot pixels and satellite trails.  With a sigma stack IRIS does really strange things with this particular data - I get weird posterisation effects that I've never seen on an IRIS sigma stack before.  I'm not yet sure if this is some genuine artifact that can be mathematically explained (e.g. maybe due to differing background gradients) or whether I'm exceeding some internal IRIS limit.

Trouble is, it takes hours to do all the processing for 130 subs.

Mark

[RobertM]

That's the trouble with these DSLR subs, you need a really powerful computer to process a lot of them !!!  With a mono camera they're done in a flash by comparison.

Interesting what you say about the artifacts.  Maybe you should try DSS for camparison ?

Robert

[JohnP]

Mark - I concur with all the other comments - what an excellent image - you must be well pleased. So many galaxies to count & all with such interesting core details/ shapes.

Nice one,  John.

PS - If its raining in France & least you can spend your time trying to process/ sort out the issues you mentioned....

[Mac]

Trouble is, it takes hours to do all the processing for 130 subs.

Is that because its doing them all at the same time,

Just a thought.

would it be quicker if you process them in stacks of say 15 and then restack the finished ones after?
10 bunches of 13 & then the final 10

It shouldn't make and difference to the finished image, but might be quicker
due to lower memory usage and less swapping out of the images.

Mac.

[MarkS]

130 subs is turning out to be a real pig to process!

Having differing background gradients (shot over several nights) really screws up sigma stacking.  So it's a waste of time trying to process them all in one batch.  Mac's suggestion is the best - create a number of substacks.  Each substack should consist of subs taken under the same conditions.

I won't get a chance to do this before I go off to France.

I also clearly have some aditional hot pixels which I need to add to the hot pixel list for cosmetic removal during pre-processing.

Mark

[The Thing]

Hi Mark,

Deep Sky Stacker lets you group subs in tabs before processing for just this scenario. You can have a common set of bias, darks and flats and then a tab for each set of lights.

[Carole]

Deep Sky Stacker lets you group subs in tabs before processing for just this scenario. You can have a common set of bias, darks and flats and then a tab for each set of lights.

Duncan I just used this method for my Markarian done over 3 different nights.

When you say common set of Bias, dark and flats:
Assuming the termperature is the same for each night and the camera has not been removed, are you saying you don't need to enter these on each tab?  Or do you mean you can just re-use them? 

I did enter them in each tab because the temperature etc was different, but just a thought for another time.

Carole

[MarkS]

I think I'm almost there - this version is 96 x 5min.

Here is a small cropped preview:


The larger uncropped version is here:
http://www.markshelley.co.uk/Astronomy/2011/hhmak_22042011.jpg

This larger version is scaled by 3/4 using 3x resampling followed by 4x binning because this seemed to give the best compromise between resolution and noise.  

The darks (library darks from a year ago) did not quite match the data, so I need to do another re-process using IRIS's "optimise dark" function.  That ought to reduce the background noise a bit further.  BTW, that is a good processing method to use (for a non-cooled camera) when the ambient temperature is changing during the session.

Mark

[Carole]

You can certainly see the difference to the background sky in this version.  Also in the full version a lovely spiral appears bottom left.

96 x 5 (8 hours !!!)
You are certainly dedicated Mark and an example to us all. 

A really beautiful image.

Carole

[mickw]

It's looking really good, the real treat though are all the faint fuzzies in the full size version.

Are some of the cores looking a bit burnt out ?

[MarkS]

Are some of the cores looking a bit burnt out ?

Yes, I forgot to add in the shorter exposures 

[JohnP]

Yes, I forgot to add in the shorter exposures 

Well shame on you Mark I think you need to start it all from the beginning again

What can I say though a truly fantastic image - one day you will have to count up all those faint fuzzies - It's really interesting to see all the different galaxy classification types in a single image.

Once you have finished it'll be good to compare your exposure time of 130 X 5 with your processing time I am guessing the latter will be at lot longer judging by all the issues you have had.

Great work though & definitely one to forward to APOD when finished... - John.

[mickw]

Yes, I forgot to add in the shorter exposures

Don't let it happen again  

Still good though

[Fay]

Really nice Mark, good job your patience & logic have kept you going through this long haul!