Confused after DSS with 30 x 120s subs

[kirkster501]

Thought this would be easy. Had moderate success with five subs. Last night got 30 or so of M31 and M33 each. The individual 120sec subs at ISO 800 show lots of details - very pleased. But after DSS with 10 x 120s darks at same ISO and 20 x BIAS the detail in final image from DSS is very dark and lacking detail. I must be doing something wrong...

Furthermore, in photo-shop all I get is a fine line on the histogram to the extreme left with a tiny bit of energy to each side of it - not the "tall triangle" I was expecting. Very difficult to "zoom" in and adjust.

Not what I thought I'd get after 30 exposures of each. Maybe I need to study this more.

Any ideas guys please?

Steve

[Bizibilder]

That is quite "normal" - surprisingly! The first thing to do is use levels in PS to "stretch" the thin black "data" so it appears "wider" within the histogram. Don't touch the RH slider (white) but play around with the central one and the left (black point) sliders - go a little at a time and maybe take 4-5 "iterations" at it (fancy word for doing the slider thing a few small steps instead of one large one). I think you will start to see your image appear from the murk!

PS Maybe worth restacking just your "light " frames to start with.

[kirkster501]

OK Roger. Thanks will take a look at that. Maybe I am not being delicate enough with the sliders. I did just stack the lights alone and it was much better.

I appreciate that mastering this is a large part of what AP is all about so will need to spend more time learning about all this levels stuff. It just surprised me that so many good individual lights gave a final DSS image looking totally bland with only a small fuzz of where M31 core would be. And after a hours worth of good data as well.....

[Rustmonkey]

I've had the same issues Kirk. I actually found I could better process single shots rather than the stakes images. PS makes the image very dark. I guess it's a big learning curve but something we'll get used to.

[spectre]

I have the same issue when I open the saved DSS image in PS. A very dark image straight out of DSS is normal for all of my images. The first thing I do is go into levels and adjust the middle slider all the way over to the right edge of the data. This spreads the data out into a usable range. Once that first big stretch is done I'll make smaller adjustments using curves, levels, and color balance to get a better image.