Ring Around the Moon, Rainbow Lunar Halo Tonight

Tonight there was a ring around the moon, a rainbow lunar halo (a 22º halo to be exact). As light passes through hexagonal ice prisms in the upper atmosphere, no light leaves the prisms at an angle less than 22° making a distinct light/dark boundary with a radius of 22° radiating out from the moon.

I believe this is my third time photographing a lunar halo - my first time was most impressive visually but faded when I went back inside to get my camera. My second time was a bit better last November in Brownsburg.

This time my lunar halo wasn't broken up by a contrail, and was clear enough to see the rainbow (or 'moonbow') effect of the light splitting into different wavelengths. These lunar halos can happen throughout the year, because the upper atmosphere can be cold enough for ice crystals even when the temperature below is much warmer - but I've only ever seen it in the colder months.

Single frame with Canon T5i, ISO 800, 18mm, f/4, 2.5 sec

Lunar halo with iPhone and NightCap app

Close-up of the lunar halo moonbow, single frame with Canon T5i, ISO 1600, 55mm, f/5.6, 3.2 sec, saturation and contrast tweaked in iPhoto

Parhelia: Rainbow Columns or Lights on Both Sides of the Sun

Having a camera in your pocket at all times (iPhone) is a huge benefit for rare atmospheric events like this! I was getting into my car in the morning to go to work and I saw this vertical column of orange-raindbow light to the right of the sun. I noticed a second one on the left at the same distance and knew it must be a sun dog (parhelion, or plural parhelia).

Parhelia on either side of the sun, taken with iPhone

As I was pulling out of the apartment complex, I tried to get a photo from my car. After driving down the road a bit, I found a good flat place with a view of the horizon and I actually pulled over on a state route, stepped out of my car, and snapped these photos. It was freezing cold but so worth it!

Panoramic photo stitched together on iPhone

The sun dogs or parhelia look like lens flares, but the crazy thing is this is actually what they look like to the naked eye! Two huge columns of orangeish rainbow light at the same height as the sun, with the hint of a circular halo. It's my understanding that these form in the same way as a 22° halo around the moon - with hexagonal ice crystals in the atmosphere.

Example of a 22° lunar halo, I took this photo back in November

Icy Ring Around the Moon

It's cold and windy here in Indiana, but there's a faint 22° halo around the moon. As light passes through hexagonal ice prisms, no light leaves the prisms at an angle less than 22° making a distinct light/dark boundary with a radius of 22° radiating out from the moon.

This is only my second time seeing a lunar halo. I got much better photos compared to my first attempt last winter.

Instagram's HDR filter really brings out the contrast along the light boundary

Beefed up in Photoshop, the halo is still pretty faint

This is a pretty good visual approximation of what was actually in the sky, very faint but definitely visible

Another shot, auto contrast and color in Photoshop

A little too slow for the lunar halo

I was taking Katie out to pee last night at 3:15am and saw my first lunar halo (at least the first since I started paying any real attention to the night sky). A lunar halo is an optical phenomenon in which hexagonal ice crystals form a 22° halo of light around the moon. The halo was very bright and obvious while I was out, but I didn't have my camera on me!!

Since the effect is atmospheric rather than astronomic, a few minutes makes a big difference. By the time I got my tripod out the icy clouds had all but moved on. I got this photo that shows a small arc around the right side - all that remained of the faint halo.

Faint lunar halo, a little too late!

This was a 10 second exposure. I don't think I needed to go that long because I've seen some great shots at ISO 200, 2.5 sec exposure time. Next time I'll know, and I'll be ready!