First (real) DSO image

[taxman (Matt)]

I finally had a night where I was able to take my time and setup a proper polar alignment. I had sort of done this before but racing clouds, kids bedtime or rogue puppy had always had me taking pics before I was completely happy with my alignment.

I have a mount that does not autoguide, and I use the ccd drift alignment method found at: http://www.minorplanetobserver.com/M...ignNoDrift.htm

So anyway, I spent a good couple of hours doing my first real imaging run with darks, flats, dark flats and bias. I think I am doing something wrong with my bias shots though - if I include them, the colour histograms are 1 pixel wide and will not stretch. I am taking 20 0.001 exposures with the cap on.

The other issue I am having is unavoidable clipping around some medium stars. No matter what I do with histograms in Deep Sky Stacker or GIMP, I always end up with unnatural black halos around medium bright stars.

My Deep Sky Stacker procedure is to drop all my pics in, let it do its thing, then align the colour curves maybe with Cyan back a little and up the saturation by 20%. I put the top part of the curves about 30-40% of the way up the loglet.

The attached is 80x90sec shots of Carinae with 20 darks, 20 flats and 20 dark flats taken through an FS-60CB. As I said earlier, I left out the bias shots as they destroy my colour curves. you can see the most egregious examples of clipping towards the bottom of the picture.

[DavidU (Dave)]

I must say for a first DSO shot that's a very good image indeed
Good work Matt !

[taxman (Matt)]

Thanks David - I should really say this is not my *first time ever*, but rather my first thought-out and planned session where I could take a few hours to get everything set up properly.

I even organised for my kids to have friends to stay over and the dog to go to my parents' house so I could keep my train of concentration.

I suppose that as it is mine, all I see are the faults.

[adman (Adam)]

try stacking just your subs without darks/flats/bias shots etc and see what you get. Then add the others in one by one to see which one gives you the artifacts. I know it will take a bit of processing time - but probably worth the exercise?

Great shot though. Is that the full FOV or have you cropped it?

Adam

[JD2439975 (Justin)]

Hi Matt, for a near first image that looks damn fine to me, just the processing that's letting you down.

IMO DeepSkyStacker is excellent for no hassles stacking but hopeless at final processing.
I've never been happy with the final image from DSS, poor colour & "blotchiness" usually being the problem.
After stacking, DSS creates an autosave.tif, this is a rather large 32bit/channel image.
If GIMP can handle this type of image I'd say use that for processing, if not then save the stacked but unprocessed image as a 16bit tif for processing in GIMP.

As Adam suggested, try just lights, lights & darks & so-on to find where the problem is.

DSS - Excellent stacker, terrible processor...
But that's just my opinion, seek professional advice.

Justin

[taxman (Matt)]

I am beginning to think it could be the Atik RGB utility.

I have tried eliminating everything but lights and have deceased the brightness to 50% in the RGB utility before stacking but keep getting the same, albeit less pronounced, clipping. It is also pretty much the same whether I save as bmp or tiff.

I don't really know much more than I have read on various fourms (i.e. nothing), but I tried duplicating the visible layer, upping the contrast until all nebulosity is gone and then putting a 30 pixel Gaussian blur before adding it to the bottom layer.

It fixes it a little, but the clipping is so pronounced, there is not a lot I can do. Perhaps it is getting lost in the 8 bit per channel conversion (GIMP only handles 8 bits at the moment).

One thought I had was that it may be occuring because I am undersampling a little (~2.7 arc sec per pixel). Could that be it?

[cybereye (Mario)]

Matt,

Great shot!

It must've been nice to have no distractions when setting up, etc. I have my sons hassling me to look through the scope before I've happily drift aligned the beast so image exposure times tend to be on the short side!!

As for rogue puppies - part of my pre-viewing/imaging ritual is to check for little surprises that our little mutt may have left in the vicinity of my scope. Nothing spoils a night quicker than stepping in you-know-what!!

Keep up the good work image wise,

Cheers,
Mario