Deep Sky Stacker Tutorial
DSS is a deceptively simple looking programme which hides some pretty powerful processing. If you speak to 50 photographers, however, you will get 50 different response on the best way to utilise this power.
I do not claim that this is the best or only way to use the tool, but I find that it works pretty well for me. As I progress and start taking more images and longer subs, it may be that I have to adapt and amend my processes to get the most out of my images. But, for now, this seems to work pretty well for me!
I am presuming you have downloaded the software and are fairly familiar with where the various buttons are. The capitals denote menu choices/tabs/buttons.
(NB, if you are stacking RAW DSLR files, make you sure have DSS version 3.3.4 otherwise the stacking will leave you with some very tall and thin images!)
So here we go, assuming you have a set of LIGHT/DARK/BIAS and FLAT frames:
- Load LIGHTS/DARKS/BIAS/FLATS.
- CHECK ALL.
- REGISTER CHECKED PICTURES.
- In the REGISTER SETTINGS box that appears I click ADVANCED and set the star detection threshold to find around 150 stars.
- Then navigate to STACKING PARAMETERS.
- In RESULT – I have STANDARD, ALIGN RGB, REDUCE WORKER THREADS PRIORITY and USE ALL AVAILABLE RESOURCES checked.
- Under LIGHTS, I chose MEDIAN – nothing else is checked in the main window.
- UNDER DARK, FLATS and BIAS I check MEDIAN KAPPA-SIGMA CLIPPING – nothing else is selected in the main window. MEDIAN settings are probably the best to ensure the processing discounts outlying images of poorer quality as well as plane or satellite trails.
- ALIGNMENT is set to AUTOMATIC.
- Everything unchecked in COSMETIC. (I was having trouble with my stars coming out like donuts and the hot pixel detection/removal settings in this tab appeared to be causing the issue.)
- INTERMEDIATE FILES and OUTPUT can be set to whatever works for you.
- Then OKAY and back to the REGISTER SETTINGS – usually I have this set to select the best 95% of pictures.
- Then OKAY to get the stack.
- When the image appears I do some basic tweaks in DSS. Firstly, on the LUMINANCE TAB, I change the bottom sliders on each of the 3 settings to 100% for DARKNESS 36.3% MIDTONE and 50% HIGHLIGHT – then click APPLY.
- Back to RGB/K Levels and with the LINKED SETTINGS box unchecked, line up the curves with each other and then click LINKED SETTINGS and move the combined curves so that it intersects the black curve (sorry for the lack of technical wording!) near the bottom bend in the curve with a good intersection between the two. Click APPLY. It the RGB curves become unaligned when moving them, simply unlink the settings and re-adjust.
- Then finally on to SATURATION and set that to somewhere between 16% and 22% to draw out some colour. Remember to click APPLY!
- I’ll then SAVE PICTURE TO FILE as a TIFF for playing around with in GIMP or a FITS if I am using STARTOOLS, although I am very much a learner with that one so we will leave that for a later tutorial!
- You can also make a selection of an area and save the image as a cropped TIFF or FITS file
Anyway, hope that helps in some way. I am sure everyone has a different way of doing things, and the results are definitely going to depend on what goes in in the first place. Some people say NO processing in DSS, while others apply a little processing, it is all, really, a personal thing, so its worth spending some time playing around to see what works for you. And, importantly, have fun with it!
Hopefully, what the above does show, is that even very small tweaks can take a washed out image and add colour and contrast to great effect!