California Nebula - Kelling Heath Ha and DSLR

[Carole]

Ha was taken on the first night when there was 8mps wind.

6 x 1200secs Atik383L Ha 12nm ED80 on NEQ6 captured in Artemis cooled to -10
Another huge object I have not imaged before.



The DSLR image was then taken over 2 nights with reduced and then no wind on the 2nd night.

total of 37 x 5mins Modified Canon 450D ED80 captured in APT with dithering.



The combined Ha and DSLR image did not come out too well, due to the alignment, and not happy with the colour, so I won't be posting that.

What a huge difference in detail between the DSLR image and CCD image.

Carole

[MarkS]

Again, a very interesting comparison.  There's so much detail and texture in the narrowband image. 
But I wonder how the Canon image would look if you displayed the red channel in monochrome?

In any case, its an excellent California Nebula! 

Mark

[Carole]

Thanks Mark.

I wonder how the Canon image would look if you displayed the red channel in monochrome?

This is the Red channel in Mono:

[Carole]

Following some new processing techniques I learnt at IOW this weekend I have now combined the Ha and DSLR data.  As you can see from the other images I did at the time they came out very pink and I have now managed to produce a combined colour closer to the DSLR image as opposed to the horrible pale pink colour I was getting before.  I have had to crop this to align the images. 

[MarkS]

That's come out well Carole, though perhaps a bit saturated.

There's also an article in November's Astronomy Now by Nik Szymanek about mixing broadband and narrowband data, but I haven't had a chance to read it yet.

Mark

[Mike]

It's a bit better Carole but the colour data in the image is still wrong. All of your stars are pink. There are no blue or orange stars. The two stars top left of the dark 'hole' in the nebula should be both blue and orange as should the two bottom right of it. In your image they are identical colours.

Take a look at this image to see how the star colours should be...

[Carole]

Hi Mark, thanks, I'll try to get hold of a copy of AN.  Yes I was wondering whether it was too saturated myself but I had been looking at it for too long, so decided to see what every-one else thought.  

Hi Mike: Thanks again, yes I struggle with star colours even with just plain DSLR, though I don't see the stars as pink in my image, I see them as white.  Ha as you know captures in mono and DSLR obviously in colour which I struggle with as regards star colour (see the DSLR image above - the stars are mainly white), but I am working on this and might re-visit CN and see if I can improve it at all.  Though majority of the stars in this image are from the Ha image and only just found out how to grab the stars back from the RGB image.  

Big new learning curve is combining filters and RGB.

Carole

[Mike]

I think you should concentrate on getting the colours right with the DSLR image only first then you can work on adding the Ha as the luminance layer. If the colours in the DSLR image are not right before you add the layer it will not come out right.

Maybe you can put your raw files up somewhere so we can download them and have a play?

[MarkS]

Maybe you can put your raw files up somewhere so we can download them and have a play?

The raw stack (linear scaled) would be sufficient  i.e. without logarithmic or histogram stretches or any other kind of "helpful" scaling applied.  A crop would do.

[Carole]

Maybe you can put your raw files up somewhere so we can download them and have a play?

That would be good Mike, I'll sort something out, though it won't help me unless Photoshop is used as I don't have Pixinsight and Iris is too difficult to understand.

Also finding problems with the differing stars sizes between the Ha and DSLR images.

Not sure what you mean by linear scaled Mark.

Carole

[MarkS]

What I mean is that if you are using DSS for stacking, for example, then we want the stacked TIF without DSS doing any "funky stuff" before you save it.

[JonH]

Iris really isn't as complex as it "looks" unless you start really messing with is.
The colour stretch tool will do wonders for the star colours and is very simple. Mark explained it too me at DSC in under 15mins!

[Carole]

Yes I've tried the colour stretch tool in Iris John, and a couple of other things, it seems to want me to input commands and statistics and I don't have a clue what to put in.

Carole

[Carole]

What I mean is that if you are using DSS for stacking, for example, then we want the stacked TIF without DSS doing any "funky stuff" before you save it.

I don't normally do any post-processing in DSS except slide the colour channels together so they are on top of each other.  If you don't want that I'll have to do a re-stack and of course the Ha won't have had that done anyway. 

Carole

[MarkS]

I don't normally do any post-processing in DSS except slide the colour channels together so they are on top of each other. 

I'm not familiar with it (I don't use DSS) but that's probably OK.