M81/M82 from Kelling Heath

[Carole]

You'll be pleased to know this is my last DS object from Kelling Heath, Just the Sun to come now which I haven't looked at yet.

Done over 3 nights, all subs 5mins 800 ISO, Modified Canon 450D no filters
SW ED120 on NEQ6, guided with QHY5, ST80 and PHD
26-9-11 - 7 subs
27-9-11 27 subs
29-9-11 - 27 subs
Total 5hours and 5mins

Stacked separately and the stacks stacked in DSS
Processed in PS CS3

Link to full frame:
http://gallery.orpington-astronomy.org.uk/albums/userpics/10047/M81%2C_M82_Kelling_26th%2C_27th%2C_28th_all_stacked_together_OAS_size.jpg

[MarkS]

Very nice image Carole.  You have brought out a lot of faint stuff there!  Again this shows how beneficial it is to:
1) Take many hours of data
2) Do it from a dark place.

My only criticism is that the image looks a bit soft - maybe a focus or guiding issue, or it might be because it is a stack of stacks which would involve the pixels of most subs being interpolated once and then interpolated again.  Can you compare the sharpness of each sub-stack against the final result?  If it is possible to process this as a single stack or for each sub-stack to use the same reference frame then this might improve the sharpness.

The core of M81 looks burnt out but maybe you don't have any shorter subs.

Overall this image is one you should be pleased with.

Mark

[Carole]

The core of M81 looks burnt out but maybe you don't have any shorter subs.

Yes was wondering about that, but never heard any-one mention it before so assumed it was all down to the processing.  Might go back and see if I can find any shorter subs I can use from the past.

the image looks a bit soft

I tried a High Pass Filter on it, but decided I preferred it without, but I'm a bit of a novice at this and was not sure what values to apply.  This is a crop and close up of M81 (core not changed as yet), after HP filter value at 42.  What do you think?


Regarding the stacking issue Mark, I find that most times when I try to process although (in groups) I get that horrid streaking on the image, but Duncan has made a suggestion that I will try of only entering the stuff that is common to all the different stacks in the first group.  I have yet to give this a try.  I'll also have a read through DSS Manual and see what it suggests.

Carole

[mickw]

Nice one.

Colours look a bit odd though in 82 and background seems a bit noisy considering the capture length.

[Carole]

Colours look a bit odd though in 82

Yes it's a tricky one to get right Mick, I tried to process M82 separately otherwise it gets washed out, then I tried to stretch the red to see if I could get any of those red filaments and failed.  I think having failed I should have adjusted the colour balance down again.

Carole

[RobertM]

Looks very good though I think processing has burnt the core out somewhat.  The background also looks a little dark but that may be my monitor here at work.

Robert

[Carole]

Thanks Mick and Robert.  I think I need to re-visit this and try another stack and process as soon as I get the chance.

Carole

[JohnP]

Nicely composed & processed - Colour (background doesn't look quite right to me) could maybe do with a small tweak. Also not sure if it is me but do all the stars look like they are marginally elongated in a top left to bottom right direction..? Did you have drift/ polar alignment issues.

Great image though - John

[Carole]

Also not sure if it is me but do all the stars look like they are marginally elongated in a top left to bottom right direction..?

They look OK to me John.  Yes the background colour does need some tweaking.
Is this better?

[mickw]

It looks more red now to me and the background has gone blotchy

[RobertM]

agreed

[Carole]

I agree that M82 has gone a bit red - I can sort that, but I can't see any redness elsewhere or blotchiness in the background.  I adjusted this image on the advice of people on UKAI who think it's much better.

So now I'm confused.

Carole

[mickw]

I agree that M82 has gone a bit red - I can sort that, but I can't see any redness elsewhere or blotchiness in the background.  I adjusted this image on the advice of people on UKAI who think it's much better.

That's odd, they are the same images and they appear too red with blotchy backgrounds there too.
Must be a taste thing 

[Carole]

Mick, can you blow me up a bit (a bit of the image that is  ) and show me where the blotches are by E mail if it's easier, I can't see any.

Carole