One of the main things I’ve learnt from my astrophotography hobby is humility. Here’s episode #743 of “what can go wrong, does go wrong”.
I use an astronomy camera that is monochrome, but uses color filters to capture color, one channel at a time. Earlier this year I was talking with my Astro mentor Rogelio, asking him why, though certain of my astro images look OK, those images made with my Red/Green/Blue filters had terrible color. He looked at the RGB channels of an image I took of the Rosette Nebula and immediately said: “that blue channel sure looks like a red channel.” As soon as he said it, I realized he was right–but how could I possibly have missed that? I’m really careful when I put my equipment together. How could I possibly have put the filters in wrong? It must be a software issue!
I went back home, opened up my filter wheel and saw this:
It looked good. I expected the red filter to be in slot #2, green in #3, and blue in #4, and it sort-of looks something like that…
But upon further examination (looking a bit closer) I notice that printed on the side of that “red” filter in slot #2 is the letter G…
It dawned on me that, a green filter reflects red light, and lets the green through. Doh!
Here are the filters, in the same order on a white piece of paper.
First reflecting light coming in through the window:
Then changing the camera angle a little:
and finally with hardly any reflected light
I must have installed them in the daytime while sitting near a window .
Hy's Ramblings 