emission


California Nebula

Buy a Print (Updated Dec. 2017) This nebula contains all 3 of the target spectral lines, hydrogen-alpha, sulphur-2, and oxygen-3. But the O-3 signal is so weak that you could literally count the photons by hand as they arrived!  To provide some color in the processed image I could have (largely) ignored the O-3 and made a bi-color image of H-a and S-2.  Instead, I used a slight variation on a commonly used process; creating a bi-color image from S-2 and O-3 (S-2 as red and O-3 as green and blue), then applying H-a as a luminance layer over the […]