I had a chance to observe a rare optical phenomenon following my visit of Mauna Kea’s observatories. On the drive down our tour guide stopped abruptly and informed us that a moonbow had formed in the distance. According to Atmospheric Optics web site “Moonbows are rare because moonlight is not very bright. A bright moon near to full is needed, it must be raining opposite the moon, the sky must be dark and the moon must be less than 42º high. Put all these together and you do not get to see a moonbow very often! To the unaided eye they usually appear, as in the small image, without colour because their light is not bright enough to activate the cone colour receptors in our eyes. Nonetheless colours have been reported and might be seen when the moon is bright.” [http://www.atoptics.co.uk/] I took a few photographs of the moonbow which turned out to be fairly noisy as I did not have time to set up my tripod and used an extremely high ISO setting.
Moon Illumination: 92%
Moon Altitude: 22 º
Time and Date: 22:36 HAST on July 5, 2012
Location: Mauna Kea, Hawaii
Optics: Canon EF 24mm f/1.4L II USM
Camera: Canon EOS 5D Mark III
Exposure: 1/4 second, f/2.8, ISO 25600