What am I doing wrong?

[Carl M]

Hi guys, I'm hoping that I can get some advice on what the problem is during stacking + processing my pictures Sorry for the movement on the stacked version, this was just from shooting straight from a tripod at cygnus. Seems after stacking the picture doesn't look good, on the preview screen on DSS the image looks better, but once saved as a .TIF and put into photoshop it looked completely different

Here is a picture of one normal sub of cygnus at 20s no editing in photoshop or anything at all:

Here is the picture after stacking 45x20s subs, 5 darks and tweaking in photoshop:

Any help is much appreciated.

Thanks in advance

Carl

[todd8137]

hi there its not bad for 20secs what was the camera settings ?

[Carl M]

18mm at f/4, ISO1600.

Point im trying to make is that 1 sub shows just as much as 45 subs stacked...which is strange. The second pic is equal to about 15 minutes of exposure but sure doesn't look like it

[pete_l]

How did you apply the darks?

I agree that there's a lot more detail (albeit noisy detail) in one of the subs. The final looks like it's got quite a restricted range of pixel values (esp. in the upper right part - just past where Vega is).

Maybe try stacking just the subs, to see what they look like before dark subtraction. You can always set the black point in PS to simulate the dark frame subtraction.

[Carl M]

I just checked all of the pictures on DSS and then changed the pics which were darks to darks, and then it created a master dark. I'll try and stack just the subs. The corners do turn strange because of no guiding or motors

[Carl M]

Seems to stay the same even without the darks.

Here though, it looks ok in DSS but once saved and put into photoshop it turns out like the above stacked picture.

[pete_l]

What happens if you stretch this image before saving as a TIF?

Also, are you running PS in 16 bit mode and saving the TIF as a 16 bit image?

[Carl M]

What do you mean by stretch the image? Also yes, PS and the TIF are both 16 bit

[JohnnyD333]

The blue isnt quite aligned with the other colors in your RGB levels, so that would fix the color. The stacked image is having issues with the corners, in both your first post and the post with the DSS processing image. Its odd because your using a camera lens and not a telescope, I sometimes get this problem and need to flatten my image or crop the corners. Have you changed any settings in DSS before you stacked. There are some good DSS tutorials out there, I wish I was more of an expert. Here is a link to a site I used when I first started, Im sure you will find some on the forums as well. Good luck!

My Quick DeepSkyStacker Tutorial Flintstone Stargazing

[pete_l]

What do you mean by stretch the image? Also yes, PS and the TIF are both 16 bit

The three sliders (red, green, blue) and the triangles underneath them. The histogram in the screenshot shows quite a narrow distribution of the colours in the image.

Moving the leftmost triangle will move the black point, the rightmost triangle will change the peak-white point and the middle one will alter the mid-grey.

I'd have a play adjusting at least the black and white points to "spread out" the histogram and make some of the dimmer detail appear. After that, save the image and import it into PS for final tweaks, if necessary.

[Carl M]

I think I may have found which was causing the .tif to go really dark after stacking and saving. Not sure if it was meant to be turned on or not, but it was called "RGB background calibration" on the light tab of stacking perimeters, I must have looked on the recommended settings before and turned it on as it said to do, hopefully turning it off will make a difference. Stacking this time is actually taking longer also.

The three sliders (red, green, blue) and the triangles underneath them. The histogram in the screenshot shows quite a narrow distribution of the colours in the image.

Moving the leftmost triangle will move the black point, the rightmost triangle will change the peak-white point and the middle one will alter the mid-grey.

I'd have a play adjusting at least the black and white points to "spread out" the histogram and make some of the dimmer detail appear. After that, save the image and import it into PS for final tweaks, if necessary.

I also noticed that when I opened the .tif in photoshop to have a fiddle with the levels, the histogram was really narrow and nearly as far left as it could be!

Once this has finished stacking I'll have a long play with the histogram and hope for the best

[Carl M]

Aha found the problem...nothing wrong with stacking, histogram or anything like that. When you save the .tif in DSS there is an option at the bottom to apply the adjustments made to the picture, or to embed the adjustments but not apply them...and guess which one had been ticked!! EMBED!!!! So the whole time I've been using DSS it hasnt been applying any changes made with the histogram, luminance or saturation...it just leaves it! Oooops Now the histogram on PS looks like it actually has a lot of data not just a thin steep line

Can't wait for some motors for my CG5 now to stop the bad corners

Thanks for the help guys

Carl

[JohnnyD333]

Glad you sorted it out. So many times I was ready to give up, and realize that the answer is right there in front of me. Gotta love this hobby.