Help with Summer Triangle processing

[Kenny]

On the morning of Thu 21st, at Arborfield Cross I went out around 2am and took 20 shots of the Summer Triangle in the hope of catching a bundle of stars and a glimpse at the Milky Way. Looking at individual frames, the data looks promising despite it not being an especially dark site. However, I can't get anything usable out of DSS stacking and Photoshop processing.

Canon 450D. 20 x 10 seconds at 21mm, f/4, ISO-1600.

Stacked in DSS. With darks, flats and bias. Also versions without flats or bias and without darks, flats or bias. The output is nowhere near as good as the original single exposure despite adjusting levels/histogram and curve in trial version of Photoshop CS6.

Any bright ideas where I am going wrong?

Note: Following images are circa 70MB TIFF files. A selection in case it's a problem with my darks, flats or bias files.

Single exposure.

20 x exposures stacked with darks, flats and bias.

20 x exposures stacked with darks only.

20 x exposures stacked (no darks, flats or bias).

[The Thing]

Hi Kenny,

A rough stretch of the stacked version (D,F & B) shows it's all there. Did you try stretching in DSS using the DSP curve tool? Also the flats don't seem to have been very effective as there is vignetting still apparent. I find this happens with DSS for some reason, usually if you repeatedly stack. Changing the stacking mode for Flats to average rather than median often sorts this out. The left hand side has a big vertical stacking artefact where there wasn't enough data at that edge, I use the Intersection stacking mode to avoid this but still find I need to trim 3-4 pixels off al round.

Could you post your DSS settings, kappa sigma value, type of debayering etc.

[Carole]

I could not get anything decent out of the one with Darks flats and Bias but I got this out of the one marked no darks flats or bias which seems to be actually labelled as no flats or bias.

The flats don't seem to have worked at all in fact may be making things worse.

This is the result I got with the one marked no flats no bias.  I had to apply gradient exterminator and HLVG (mild iteration).  It's showing quite a bit of detail, but still a gradient at the bottom.

Carole

[Kenny]

Thanks Duncan.

Did you try stretching in DSS using the DSP curve tool?

Er, no...  what is that?

20 lights, 5 darks, 6 flats, 13 bias (bit of a random selection, not sure why I did that). All in CR2 RAW.

Could you post your DSS settings, kappa sigma value, type of debayering etc.

I'm using out of the box settings - I've never changed the DSS settings other than the Star detection threshold (which was set to 2%), mainly because I've no idea what most of them do and stacking with out of the box settings has worked in the past (and mostly what the YouTube videos I've watched have done).
Stacking Paramters:
* Result: Standard Mode
* Light: Avergage
* Dark: Median
* Flat: Median
* Bias: Median
* Alignment: Automatic
Under Recommended settings it does say (didn't notice before) I am using a low star detection threshold and suggests applying a median filter before registering images to reduce the noise and improve star detection. (which I didn't)


Thanks very much Carole. Very good to see evidence I have some usable data if I can figure out how to process it correctly.
My flats also don't appear to be working.

This is the result I got with the one marked no flats no bias.  I had to apply gradient exterminator and HLVG (mild iteration).  It's showing quite a bit of detail, but still a gradient at the bottom.

Did you stack that in DSS or Photoshop?
p.s. unfortunately I don't have the gradient exterminator or HLVG. Are those donwloadable? Free? Cost?

I got this out of the one marked no darks flats or bias which seems to be actually labelled as no flats or bias.

Not sure what you mean here. The links and text descriptions look fine to me.

[Carole]

Did you stack that in DSS or Photoshop?

I thought that was already a stack, so I didn't do any stacking.

Not sure what you mean here. The links and text descriptions look fine to me.

Well when I went to save my processing as a PNG file so I could post it up, it didn't like the commas in the title, so I took them out, it's slightly possible I deleted one of the words in your file as well but I hadn't been aware I had done so.

Carole

 

[Carole]

I don't have the gradient exterminator or HLVG

Yes these are both plugins.  GE is paid for I think it was something like £32 when I bought it but it might have gone up a little.
HLVG (Hasta la vista green) is free I think. 
http://www.deepskycolors.com/archive/2010/04/26/hasta-La-Vista-Green.html

Carole

[Kenny]

Did you stack that in DSS or Photoshop?

I thought that was already a stack, so I didn't do any stacking.

D'oh. My error. Yes, of course it is already stacked. Blonde moment. 

[Carole]

My flats also don't appear to be working.

Make sure you haven't over-exposed your flats. 

Take a look at the histogram of the individual flats, it shouldn't be more than 50% or less.
Also take a look at the master stack flat and see if you can stretch it in Brightness and contrast in photoshop, (keep darkening it and brightening it to see if you can reveal vignetting and dust.  If all you get is a white image then you've over-exposed it and it won't work. 

Carole   

[Kenny]

I adjusted the camera settings until the flats were middle of the historgram, but at the moment I've been experimenting with excluding the flats, bias and darks just to get a usable DSS output.

In photoshop, as soon as I start to stretch the histogram or apply a curve I get a horrible clipped gradient across the image and still nowhere near the detail of a single exposure.

[Carole]

Just realised this is an unmodded camera, and can see the NA Nebula, also the coathanger shows up well.

Carole

[Kenny]

Just realised this is an unmodded camera, and can see the NA Nebula, also the coathanger shows up well.

But unfortunately this data has defeated me. Think I need another tutorial. Still can't extract anything usable from any of the stacked images (with or without darks, flats or bias).

[Carole]

Pop over with your laptop and data Kenny, I'll give you another processing session.

We can get those plugins installed while you're at it if you wish. 

Carole

[Kenny]

Thanks Carole. I'll drop you an email about this.

[Kenny]

Had another go at this, this time using the latest version of Adobe Light Room via Creative Cloud (trial). At least I can see the data now. Still some work to do. This is the version without bias or flats (I think there was something wrong with the ones I used and I should possibly takes some new ones). I am disappointed by how much aberration there is round the edges of the (already cropped) image.



Further feedback or advice welcome.

[Carole]

Getting there Kenny, try balancing your colours and give it a little bit more stretch.

Carole