astrophotography

There was quite the auro­ra show last night, and I’m going through my pho­tos from that, but first I decid­ed to process the 24 shots I took of the Milky Way. Two hours’ pro­cess­ing gets you the above photo.

The Process

I took some notes as I processed the images, because I want to do more of this and get bet­ter at it. The image, as eye-catch­ing as it is, is pret­ty noisy, and I’m pret­ty sure there are bet­ter ways to do some of the things I did. But, for the nerd crowd (I know you’re out there, I can hear you breath­ing), here’s how I made this par­tic­u­lar image:

• snapped 24^[1]One frame was wonky, so the final stack is 23 images deep. pho­tos (aka “light frames”), 15 sec­onds, 24mm, f/2.8, ISO 3200
• snapped 3 dark frames, ie, left the set­tings the same and put the lens cap on
• did dark frame sub­trac­tion on every frame (opened each light frame and a dark frame in Gnu IMP as lay­ers, dark frame on top, and set the Lay­er Mode to “Sub­tract”)^[2]This gets rid of the cam­er­a’s “hot pixels”—the first time I tried stack­ing the images, I got smeary blue and red lines from the hot pix­els.
• align images with align_image_stack -a aligned_ *.JPG ^[3]Part of Hug­in.
• con­vert aligned images to JPG using mogrify -format jpg *.tif^[4]part of Image Mag­ick. (most­ly so I don’t over­load my poor laptop)
• open aligned images as lay­ers in Gnu IMP
• set each lay­er mode as “Dodge”
• export­ed the whole she­bang as a JPG
• re-opened the export­ed JPG
• Used Gnu IMP’s Fil­ter → Enhance → Noise Reduc­tion and cranked that baby up to 11 ^[5]16, actu­al­ly.
• prof­it

Things to try next time:

• shoot RAW
• try a low­er ISO value

It was clear last night, so off I went to Rid­ing Moun­tain to get some Milky Way pho­tos. I shot a cou­ple of panora­mas, one just off the high­way on the golf course / Wish­ing Well turnoff, the oth­er at Spruces (thanks again, Tim!).

As I was leav­ing, thin clouds had start­ed to roll in, and the moon—still half-full—was ris­ing in the east.