DSS - what am I doing wrong?

[Ags]

When i stack my images, my image gets brighter in proportion to the number of subs I stack.

This makes no sense to me. I do a simple median stack so presumably each pixel should have no more than the middle brightness from the stack. Instead my final image is white.

Pre-stack single sub:

Post stack whiteout:

My stack settings:

[lensman57]

I think that this is normal, you could drop a fits file in dropbox if you  wish and we c what could be done with it.

Regards,

A.G

[Ags]

I don't get it - how does a median stack make the background brighter?

[bogdog]

if you check your histogram  you find data to the far right rather than being to the left or midway

just by adjusting the image you posted and shifting histogram back to left i get this

not perfect as i'm colourblind,but sure you could improve on original

[Alien 13]

I get the same problem my stacked image is very bright but then again my subs are similar to yours maybe even a little brighter it does seem better if i use flats and darks etc.

Alan

[bogdog]

i think after you have stacked all your images you still need to do a final processing in photoshop or whichever paint app you use

i dont think stacker will give you a final finished picture...i could be wrong though

[crimpshrine]

It's a bit brighter than my tend to come out but so is your single pic.. Once adjusted is PS you will reveal all the detail. I thought it was odd the first time but all the details will be there when edited.

[Ags]

Well, I am not happy and I am not impressed. A median derived from all the subs should be no brighter than any of the individual subs. As far as I can see, the result is simply mathematically wrong. With the histogram so far to the right I have lost one or two bits from the image, and colors in the stars are lost.

[Sandancer10]

As Bogdog said "your histogram is too far to the right". To correct it you need to go onto each R G & B channel and move them to the left (black point) end of the histogram. Try different amounts, but try and always end up with the RGB in one spike so you don't end up with a colour caste.

[Ags]

Yes, I know how to correct the histogram, I am trying to understand why DSS gets it wrong in the first place.

[keyser187]

hi, i have no clue wot im talking about lol but just thought id throw stuff out there. Have u changed then brightness of the subs before stacking with the FITS/RAW settings?

also have u tried stacking with the "set black point to 0" UNTICKED?, i use a 1100d and my preview of my subs have a purple wash in DSS which i think is to do with the WB,unticking the box makes my subs black again.

[dph1nm]

Turn off  RGB Channels Background Calibration and see what happens. This does some automated scaling of the channels, so it is always possible this has gone wrong for some reason.

NigelM