Saturday, March 12, 2022

Circum-zenithal arc in Taurus from a 5-day crescent moon

This is one my most unusual images. I caught a circum-zenithal arc while taking a picture of the constellation Taurus:

This image was taken with a 50 mm lens, which has a field of view barely able to fit the arc.

For comparison, here is a circum-zenithal arc in front of my home:

Until my Taurus arc, all images of circum-zenithal arcs I've seen are in daylight with the sun as the light source.  I included my house when I took the photo so I could use it to identify the zenith.

Here's my attempt to position Taurus in the same setting:

This photo was taken a week after the arc and I wasn't diligent about the time, but I hope it shows that Taurus is well-positioned to host a circum-zenithal arc at dusk in early February.

Here, I rotated the arc photo to match the orientation of my wide-field Taurus image. The arrow shows the direction of the 5 day crescent moon that was present at the time I took the photo.

For additional verification that this is a circum-zenithal arc, and not the more common 22-degree halo, here is a view of my location and time when I took the image: