New Color Module woes

[gboulton]

Hrmmm....

Well, now, I'm getting some pretty strange results here.

When I get to the color module, I can run all three sliders to their absolute max...and get NO change. Nothing. Not so much as a pixel's difference. It's as though there's no color data there.

[admin]

Hrmmm....

Well, now, I'm getting some pretty strange results here.

When I get to the color module, I can run all three sliders to their absolute max...and get NO change. Nothing. Not so much as a pixel's difference. It's as though there's no color data there.

Yep. Seeing the same thing here. I'm downloading Gustavo's RAWs now to see if there is any color data in those...

[admin]

Ok, I had a look at the individual frames as well. They definitely contain color data. It appears something went wrong during the stacking stage resulting in a black & white image!

[gboulton]

Ok, I had a look at the individual frames as well. They definitely contain color data. It appears something went wrong during the stacking stage resulting in a black & white image!

So...what we're after here is a version of the color module that works with Luminance data only

[admin]

So...what we're after here is a version of the color module that works with Luminance data only

Well, joking aside, you can actually use the Color module to create a false color version of your b & w image. It's useful for Solar images for example.

[gboulton]

Well, joking aside, you can actually use the Color module to create a false color version of your b & w image. It's useful for Solar images for example.

Quit it, Ivo. I'm tryin' to be a smart-ass over here...

[gustavo_sanchez]

Ok, I had a look at the individual frames as well. They definitely contain color data. It appears something went wrong during the stacking stage resulting in a black & white image!

Hello,

I have seen that before. The stack was generated using Nebulosity and definitely has color information, since it was generated from color frames. It's just that when I open it into ST, I don't get any color. It's very strange. This is a problem I mentioned here before in another post. It did not happen before, and I have been using the same version of Nebulosity all the time. Before, I could import my stack in *.fit format into ST without problems (it was in color); now I have to save the stack in Nebulosity as a *.tiff to be able to get color in ST. Don't know the root cause of it yet.

If you want, I can send you the stack in *.tiff format.

Thank you for helping us users, you are very kind.

[admin]

The stack was generated using Nebulosity and definitely has color information, since it was generated from color frames. It's just that when I open it into ST, I don't get any color. It's very strange.

After inspecting the FITS file with a hex editor, I think I know what's going on. It appears Nebulosity has been saving the color channels as separate FITS extensions (or HDUs). The latter is not the correct way of saving color data and (to my knowledge) is only used by ImagesPlus.

From the Nebulosity 3 manual (page 26);

"The differences are esoteric to most (and concern using 3 HDU's vs. using 3 axes) until one realizes that programs using one standard don't generally like files written by the other standard. So, Nebulosity will not only read both formats just fine, but it'll write either of them. They're labeled RGB FITS: ImagesPlus and RGB FITS: Maxim / AstroArt."

So, save your images using the RGB FITS: Maxim / AstroArt setting and things should work fine!

As an aside, the reason why using 3 HDUs (header/Data Unit) is 'wrong', is that they do not convey what exactly those 'extra' data chunks pertain to. Nowhere is it specified which channel is red, green or blue, or if they are even different color channels of the same image! For example, the Hubble Space Telescope stores bad pixel maps and other data in the subsequent HDUs, not color channels. To my knowledge it is only ImagesPlus that saves/reads FITS like this though. The trouble here is that no software can autonomoulsy guess what the correct way of interpreting the data is, unless it is told that the data file originated from ImagesPlus or unless it makes assumptions that may be wrong. Using 3 axes (dimensions, e.g. width, height, color channel) is the correct, coherent way of storing a color image.

[gboulton]

I don't know how many kinds of awesome there are, Ivo...

But you are all of them.

[admin]

I don't know how many kinds of awesome there are, Ivo...

But you are all of them.

Gee, thanks Gordon. Just doing my (self appointed) job!