A Dark Sky Comparison

I was recently in the Mayhill area of New Mexico and really enjoyed the dark skies there. The stars and winter Milky Way were just fantastic. While I knew it's much darker in NM than at my home in Melbourne, I thought I'd take dark sky comparison photos to see the difference.

My new Canon PowerShot S95 camera has their high performance low light HS System that would be great for this type of picture. I set the camera to full manual mode: ISO 3200, f/2.0 and 15 seconds. Using a photo tripod I took a series of images around
the horizon. To the eye, the horizon was completely black. But the camera revealed this low broad light dome from nearby Cloudcroft. But the sky darkens quickly up from the horizon. Also note part of the Milky Way is easily visible rising from the
horizon on the right side of the picture.



Returning to Melbourne I took a similar image from my back yard using the same camera and same settings. I shot the photo to the west, which is my darkest part of the sky. I live on the north side of MLB and it really doesn't seem too bad for this area. This is where I do all my astro imaging and I've taken some nice pictures from here. But this photo shows how not dark it really is! In fact, if it weren't for Orion in the sky, I'd think this was a daytime photo!



It's not surprising then that my better astro photos are the stacked images taken with really long total exposure times. Stacking many images reduces the noise to the low levels needed to pull details out from the very edge of our skyglow.

Rick Young
Feb 28, 2011