Nebulosity 3, RAW colour conversion

[TanjaC]

Hi guys.
I normally shoot all my subs directly through Nebulosity as FITS files, through a DSLR so it comes up as colour as it shoots.

I can (and have before) open CR2 RAW files, but then have to run the 'Batch Demozaic and Square RAW colour' function to make them colour images prior to stacking.

But when I use Milky Way photos, it makes them pink and takes away all the data of the stars. Anyone know why and how I can overcome it? In Photoshop you can see nice detail in the single exposure, so the data is there. (as per attachment; left RAW / right Nebulosity converted)
Wanna stack my subs to get a better image but Nebulosity doesn't wanna know about it!

Thanks

[whzzz28]

All i can think of is that it is light pollution.
I grabbed an old DLSR image i had from when i first started.
I get the same thing, but more blueish. I had a LP filter on which gave the image a blue tint.

To remove it you need to get rid of the color cast.
Nebulosity 3 does a decent job of this.

Go Image -> Adjust Color Background (offset).
It will automatically try and find the best setting. If its still redish or whatever, you can play with the sliders.

Click ok and see how that goes.
See attachments for an example.

[TanjaC]

YIP - works perfectly - THANKS.
I did a test stack of all my FITS files, and then Adjust the colour of the final stack, but it doesn't work well. Went and ran the change on individual pics (3) and then stacked them - and works a lot better. Strange. So I have about 20 images to run through.

As per attached images, when Adjust Color Background is applied, the "display" is stretched but not the original file - so post colour adjust i stretched the levels to the same B&W values as the preview. Worked well.

Then took the file to photoshop to finish off.

It's a tedious process. I'm really just tempted re-shooting it through Nebulosity so they all come out FITS and great colour from the start. (or save for a cloudy night)

Thanks again for the help. I hope what I listed above can be of future use to someone....

[Carl]

Hi Tanja
Nebulosity used correctly is an outstanding capturing and processing tool. I have been using it for about 4 years now, hated it to start but now i love it.

Firstly i suggest you read from cover to cover the manual, then download Craig Starks excellent guide" PrepProcessing Walkthrough. Again read it from cover to cover, there really are no short cuts.

I shoot with a canon DSLR and only capture to computer FITS. From my experience the FITS files just seem to have a whole lot more info in them to work with.

Make sure you shoots lots of subs and pay particular attention to your histogram, If you have pink stars then you have over exposed and saturated the image.

All of my serious post processing is done in Photoshop. If you want to see the results type my name in in the deep sky images section of IceInSpace.

Once again make sure you read the manuals and tutorials.

Regards and good imaging

Carl Rainer

[TanjaC]

Hi Carl, thanks. I'll look through your pics...

I also only use Nebulosity to shoot through. That is why this was an issue for me doing CR2 Raw files. I'm used to having FITS files and being colour already.

So opening and converting the RAW files was a learning curve. I did manage to come right, but it meant Auto colour adjustments as whzzz28 suggested, and then further stretching it a lot!

But in future I'll just keep shooting through Nebulosity.

Quick question - do you shoot Flats through Neb as well? As those are such quick exposures I've done them all as RAW files just through my cam. And now I'll have issues converting them too to colour?

Here's a link to that final file I did
http://www.flickr.com/photos/astro-tanja/8025869788/in/photostream

[Carl]

Hi Tanja

I don't shoot flats and i don't shoot darkframes.
I use bad pixel map instead of dark frames and use Noel Carboni's Astronomy tools plug ins to combat lack of Flat frames.
To be honest the shutter on these dlsr camera does not have a long life and i really cant afford to waste images. Foe example i know people who have not managed for than 20,000 clicks woth the Canon 1000.

Process all of your images in the order recommended in Nebulosity, the last stage of the process before stacking coverts all to colour

Any assistance needed just let me know

Regards
Carl

[Carl]

Hi Tanja
Just had a look at your image on photostream. I notice you are using the new 60DA. Did you set an in camera custom white balance before shooting to match the temperature of the stars?

Regards
carl

[TanjaC]

Nope, have not set custom white balance. Was still using the daylight WB. I've not really shot with this cam a lot, just moved over from an unmodified 5DMII. I'll do some research into custom WB on this if it should make a big difference.

Thanks
(Subsequent to our posts I've opened up a whole new can of worms with my PHD guiding that's dropping guiding due to saturated stars. hmmm... it never ends.)