Need help with Trifid

swannies1983 (Dan) · #1 31-07-2011, 09:28 AM

I made my first attempt at imaging the Trifid last night. I only had time to take 20x1min ISO1600 subs. Pics were taken in RAW format. I soon came to the realisation that RAW images are imported into DSS as gray 16 bit images, meaning the imported images and the final stacked image, don't show any colour (see first image). After doing some reading, this is normal and the way to bring out the colour is to increase saturation to about 20-25%. I tried this but it doesn't appear to work very well (see second image). It does bring out some red, but no blue, despite clearly being red and blue when looking at the images on the camera. I'm sure others have experienced this so any advice would be great

EDIT: I think I figured it out. I found that someone suggested that you save the stacked image as a TIFF file first before processing. Plus, reducing the resolution appears to remove some colour so I have included a link to a larger size

Again, I assume the elongated stars towards the bottom left-hand corner is a coma issue?

CapturingTheNight (Greg) · #2 31-07-2011, 05:30 PM

Hi Swannies,
I'm new to doing astrophotography and using DSS, but I may be able to help from what I discovered so far. When the image has finished stacking and alligning in DSS I simply save it as a 16 bit Tiff and exit. Don't worry that it is grey in appearence. I then open it up in photoshop elements 8. I don't have full PS yet. It initially comes up as a dark image. I use the levels control to gradually bring up the exposure. I move the middle slider a bit to the left of the exposure histogram (Don't try to do it all in one go). Close the levels tool, and then open it up and move the middle slider a bit more. After doing this close and open routine a few times the exposure histogram should have moved off the left hand side and be somewhere between the left and middle. The image should look fairly bright. You can then move the left hand slider in towards the right to darken the background of the image. Be careful not to move it to far into where the histogram is or you will start to lose data in the object. Only when I am happy with how the image looks with the levels, do I then increase the saturation to bring out more colour otherwise I have found it will saturate any background colour. I also do the saturation in a couple of steps. For example take it to say 20%, ok it, open it again and do say 10% more.
I hope how I do it gives you some help.

swannies1983 (Dan) · #3 01-08-2011, 02:27 PM

Thanks for the info. I will look into it

Poita (Peter) · #4 01-08-2011, 06:38 PM

Remember that you can get a 30day trial of photoshop free too if you want to try it out.
If you use sandboxie to install it safely you can *completely* remove it at any time, including all registry, hidden files etc.
Sandboxie is a great way to run programs in a sandbox, safely where as far as the rest of the pc is concerned, you never installed it.

midnight (Darrin) · #5 03-08-2011, 06:51 PM

The image in DSS is not grey even though it appears grey and dark. It is most likely your camera is 14 bit and DSS is working in 16 bit so the image eventually needs stretching in say PS or your preferred choice.

Your first image appears like a normal unstretched colour result one would expect from DSS even though you mention it looks grey.

Cheers,
Darrin...