Astro Session: June 22, 2018

June 22, 2018 - Reading time: 2 minutes

The view from my backyard, with the right equipment focused on a particular part of the sky: Cygnus Wall region of NGC 7000, the North America nebula, imaged in narrowband Ha and OIII. The way narrowband imaging works is by filtering out all light except for an allowed narrow bandpass at specific locations in the electromagnetic spectrum. A hydrogen-alpha (Ha) filter will only allow light to pass through to the camera sensor around 656 nanometers, which is out at the red end of the spectrum, and an oxygen-3 (OIII) filter will only allow light to pass through around 501nm, which is in the middle of the blue and green ranges. When I say red, green, blue, I'm talking about where these bandpass lines fall within the scope of the visible spectrum, which starts around 390 and goes to 700 or so (for humans). I shot the oxygen-3 sub-exposures last week, and the hydrogen-alpha subs last night. When you process these separately filtered images into one color image, you may get the Ha coming out vivid red to rust red, and the OIII coming out in blues and greens. The Cygnus Wall is that bright, rolling line across the middle where you have a lot of concentrated star formation, but this area of NGC 7000 also has lot of dust and debris drifting in front of it--the dark reddish-brown regions across the top and right side. (Imaging info: 42 x 300 second subs in OIII, 40 x 300 sec. subs of Ha. + 20 dark frames stacked in DSS, processing in PSCC2018 + Astronomy Tools actions & Annie's Astro actions. Equipment: William Optics ZS61, Atik 414EX mono CCD, 7nm Optolong 2" Ha filter, 8.5nm Baader 2" OIII filter, CEM25P EQ Mount, ZWO ASI120MM-S Guide Cam,