Beautiful Sunsets

My work “day” at Kitt Peak National Observatory gets going in earnest when the sun sets. We have a saying at the observatory that beautiful sunsets mean poor observing. For better or worse, we’ve had some beautiful sunsets this past week.

There is some truth to the notion. Clouds can make dramatic sunsets, but they also obscure the view of even the most powerful optical telescopes. Red sunsets are often caused by dust or smoke in the air. Both are bad for observing in their own right. They make the sky hazy, but they can also settle out on telescope optics, which then becomes a problem when the weather gets even better. Unfortunately, big telescope optics are not easy to clean and the particulates can even damage them.

The wind that kicks up particulates or dries out the brush, giving us fire conditions, can also be a problem for observing. An unsettled atmosphere can make objects magnified with a telescope look fuzzy and distorted. It’s what we call bad “seeing.”

Nights with these kinds of poor, but not stormy conditions, can be the most difficult in my work life. We have to be ever vigilant to make sure the winds don’t get too high to safely operate the telescopes or the clouds don’t build up to ones that might drizzle. Even a little bit of water on telescope optics can ruin a telescope operator’s night. The wind can actually blow the telescopes around enough that we have a difficult time tracking targets precisely.

Our best nights are those when the sky is clear and calm at sunset. A few high clouds on the horizon aren’t ideal, but they’re not necessarily terrible. This was a sunset taken on a pretty good night.

This sunset’s pretty cool because I caught just a little of the “green flash” effect. I was just using the camera on my Kindle, so it doesn’t look as green as it did watching it, but you can see the after image of the sun just above the setting sun itself. That’s caused by atmospheric dispersion stretching the image of the sun like a prism or a rainbow. So you see the green/blue light of the sun set after the yellow light.

So, yeah, you can have pretty sunsets on good nights, too. They may just be a little less dramatic than the sunsets on the difficult nights.

If you want to see what happens when I imagine a truly dramatic night at an observatory, read my book The Astronomer’s Crypt. You can learn more about it here:

Like telescope operators, vampires also come out when the sun sets. I imagine a vampire telescope operator in my novel Vampires of the Scarlet Order. Read a sample chapter and learn more at: