DSS dark output?

[JB80]

Why is my DSS outputting very dark pictures after stacking like the one below?

That's just over 4 minutes of exposures and I can't do a thing with the image it puts out, normally it would give a grey image but for some reason whatever I try it now puts out a dark one.

You can barely see the stars in the compressed jpeg but in the tof they aren't much brighter.

[Spikey]

Don't want to state the obvious Pibbles but has the luminance curve altered at all? Maybe the histogram is sitting outside of the range?

[JB80]

Anything is possible, although I don't know what the original luminance settings should be to check it against or how it may of come about that it changed.

You could be right though.

[jgs001]

Can you post a single input sub, and a screen shot of DSS once it's completed processing, but before saving ?

[JB80]

Yep, give me a little bit to run it through again and I'll post the screen shot.

Here is a jpeg of one of the RAWs in the meantime although it doesn't really matter what batch of images I try the result is all the same. I know they're not really the best set of subs but I'm only trying to experiment. I haven't had this problem before using similar or worse type subs.

[JB80]

OK, here is the screenshot. Although this time it only stacked 3 frames, it has been stacking 4 minutes worth of frames but the end result is the same.

It had 22 detected stars.

[jgs001]

There's something odd going on with those levels... look at the end points on the right... also, the peak of the histogram is well to the left... you can try and tweak that with the luminance tab to move the diagonal into the histogram.

[JB80]

That's the thing, tweaking the RGB sliders doesn't really do much and if I move the luminance into the histo I get a horrible noisy image like below.

Plus when I then go to stack another lot it automatically goes back to the dark output posted above.

[jgs001]

Can you post some screenshots of the raw/fits settings and the stacking parms ?

[JB80]

Sorry about the delay, here goes.

[jgs001]

Ok, what happens if you do a standard stack instead of mosaic, and turn off the cosmetics ?

[JB80]

I just tried that and I get the same dark output although it shows the stars that do show slightly brighter and when I adjust the luminance there is less noise but it's still not great.

I wonder if a reinstall might be of any use.

[Spikey]

I would also have RGB align checked. The curve doesn't look quite right and the histogram is too far over to the left. Only got my phone to check Pibbles but I'll get on a proper computer later and take a proper look. I'll also see if I can draw how the curve should look and where the histogram should lie on it.

[Spikey]

That's the thing, tweaking the RGB sliders doesn't really do much and if I move the luminance into the histo I get a horrible noisy image like below.

Plus when I then go to stack another lot it automatically goes back to the dark output posted above.

I could be getting this wrong here because I don't have DSS to play with but I'm going to suggest it anyway. The midtone sliders look the wrong way round. I think the bottom midtone slider should be slightly to the right of the top midtone slider.

Humour me and try it

[JB80]

You're right, in that pic I had moved the bottom midtone slider to the left to bring some kind of detail out of the dark picture. If it was in it's normal place it just goes back to the dark image.

This tutorial is shows how it normally looks for me after stacking if you scroll down to the picture just before the "curve adjustments" section.

http://flintstonestargazing.com/2009/06/26/my-quick-deepskystacker-tutorial/

At that point I'd take the grey image and use curves in PS.

However after stacking it's coming out like the pic below. It's like the histogram settings have changed. I'm sure the answer is simple but I haven't changed anything knowingly.

Tomorrow morning I'm going to re-install and see if that makes any difference.

Thanks guys too for having a look at this.

[Spikey]

You're welcome Pibbles. The histogram looks too far over to the left, set the RGB to be linked on the first tab and adjust the sliders so the histogram moves over to the right. Go far enough so that the bottom part of the histogram is about in the middle of the curve and see if that helps. Don't see much point in re-installing a the program is functioning but it might reset everything to defaults.

[Stephen]

(Snip) Ignore that, reading the thread properly now

[jgs001]

Are you using Bias frames ?? I don't see a mention of them.. but your forcing the black point to 0 which only really works when using Bias. In the RAW files setting tab, uncheck the set black point to 0. I'm sure I had the same symptom a while ago. Sorry I didn't spot that earlier.

[dph1nm]

This looks perfectly normal behaviour for DSS. If you want to see the image in DSS you must move the bottom mid-tone slider to the left so that the black line cuts through the lower end of the histogram. DSS virtually never gets this right on its own.

NIgelM

[Jgw]

Hi Pibbels,

I have noticed in the Fits Files you have not declared your canon 450D..

Give it a go ...

Cu John

[Spikey]

Hi Pibbels,

I have noticed in the Fits Files you have not declared your canon 450D..

Give it a go ...

Cu John

I wouldn't do that unless you are working with FITS. I think Pibbles output will be RAW CR2's or jpg's or maybe both.

[Keiran]

Not sure if this is much help, but when you input the light subs, select 1 sub and in the top right there is an adjuster. Have you tried adjusting this first and then stacking them. After it is stacked i think the histo needs to be aligned and moved to the right abit.

Sorry if that is useless info but thats all i can suggest

[JB80]

Righto, lots of stuff to try.

Keiran, I haven't tried that but it's worth a go because it seems like I need to adjust the histo before stacking, if I change it after stacking the damage is already done to the stacked image so to speak.

Also, yep I'm using just RAWs and not using FITS.

I'm not using Bias frames just darks so I'll try unchecking the black point.

Sorry for the delay, I'm a bit busy toda but I'll try the suggestions and see what happens.

[Keiran]

Well good luck look forward to the results

[Spikey]

Yeh good luck Pibbles, likewise, looking forward to the results.