Tuesday, May 28, 2013

Venus, Jupiter, Mercury Conjunction (1080p, 30fps)

The planets Jupiter, Venus and Mercury are close together in the evening sky this week, so every night I've been trying to capture them together on the horizon in the twilight hours before they set. The first night the clouds were too thick. The second night I was shooting sunset in high winds at Mono Lake with the Sierra Nevada as a high western horizon, so I caught a few pictures of the planets, but they set too quickly to capture a time-lapse video. The third night was just right, relatively clear to the west, I was in a high shooting position with an apparent horizon lower than my position (less than 0 degrees elevation), and fortunately that was Sunday May 16, the night when they'd be closest together, forming a tight triangle.

There was still wind to deal with so I changed position a few times to minimize it. I could only use one camera because I had loaned my daughter one of my quick release plates the day before and it was still on her camera back home. There wasn't a lot of light and I was shooting with a 2X teleconverter on my 70-200mm lens at close to 310mm, so my aperture was limited to f/8, forcing me to bump up the ISO to minimize shutter speed in that wind. Fortunately I worked out all the trade-offs in time to capture about four hundred frames, enough to create this time-lapse video. 

Here's how my four days of effort to capture this event turned out:

Pursuing the Venus, Jupiter, Mercury conjunction on May 24, 2013.
May 24 from Lake Tahoe

Pursuing the Venus, Jupiter, Mercury conjunction on May 26, 2013. Too high of a horizon at Mono Lake!
May 25 from Mono Lake

Pursuing the Venus, Jupiter, Mercury conjunction on May 26, 2013, just right with a low horizon.
May 26 from Monitor Pass

Pursuing the Venus, Jupiter, Mercury conjunction on May 27, 2013. Too cloudy over Lake Tahoe!
May 27 from Lake Tahoe

Friday, May 17, 2013

Rainbow in a Sun Ray

Last night I caught a sun ray rainbow, just before sunset, at Topaz Lake on the Nevada/California border.  

You may have noticed that rainbows move as the sun moves.  White light contains all of the colors of the rainbow, and the rainbows we see are simply that light separated out into various wavelengths, which we perceive as colors.  This doesn't happen like it does with a prism, where the rainbow comes out the back side of the prism and that color-separated light is projected onto something.  Instead, raindrops do separate the colors of light through refraction, but instead of it escaping out the back, that light is reflected back out of the raindrop at a 42 to 43 degree angle.  So everywhere you see rainbow color is a raindrop, and if you draw lines back from that rain drop to yourself and to the light source, those lines meet in roughly a 43 degree angle.

Someone standing a mile north of you may see a rainbow, but their rainbow will be coming from a different set of rain drops making a 43 degree angle back to the sun, and their rain drops at that angle will also trace a "rainbow-shaped" arc in the sky.  This is why you can see rainbows while you drive, and they will appear to move and follow you (at that same angle to the sunlight) as you drive.

So as a photographer, if you don't like where the rainbow is, move!  As long as you don't move so much that "your" rainbow doesn't fall off the end of the column of water it's coming from and disappear into dry air, you should be able to place the rainbow where you want it.  Similarly, if you see the sun striking a column of water and the sun seems to be close to the right angle, simply move until you catch that 43 degree angle and can see and photograph the rainbow you anticipated that it was making.