Venus Transit Retro-Blog: Transit Day, Part 3

The 13 observatories on Mauna Kea are scattered at different locations around the upper mountain.  Optical and infrared observatories are on the high ridges.

This is the last switchback before you reach the highest observatories on Mauna Kea.

Submillimeter telescopes are clustered just below the summit. From left to right: CalTech Submillimeter Observatory, James Clerk Maxwell Telescope, the Submillimeter Array

Just below the optical/IR telescopes is an area known informally as “Submillimeter Valley.”  The observatories here house microwave-band radio telescopes. The very short wavelengths — just barely longer than infrared light — mean that that submillimeter telescopes don’t need the huge dishes usually associated with radio telescopes.  The observatories in Submillimeter Valley are among the most sophisticated facilities on the planet, but they don’t get a lot of publicity. I suspect it’s because radio astronomy doesn’t lend itself to the beautiful astrophotos that adorn so many books and magazines.

Summit visitors pose for photo with clouds and Mauna Loa in the background.

This photograph, and the one above of Submillimeter Valley, show the clouds swirling around Mauna Kea. That actually leads into to the next phase of our Transit Day activities.

The original plan was to observe Venus’s egress from a hill near the VIS.  It looked as though the clouds around Mauna Kea might obscure the Sun for observers on the hill. Our group organizers hurried off to scout alternative locations.

As it turned out, one of the most likely prospects turned out to be the beach behind our hotel. So, a good many of us decided to make a quick trip back to Waikoloa Beach. We got back shortly before the predicted time for Third Contact, and we scurried to set up. I imagine the other hotel guests must have wondered about the people stampeding into the lobby. A herd of astronomers, carrying packs and equipment, many of us still wearing warmer clothes, must have been a bizarre sight for Hawaii!

Our observing station for Venus’s egress

Hawaii was at the edge of the region where the entire 2012 Transit of Venus was visible, so we were observing near sunset, through a considerable mass of warm air. Having seen a crystal-clear ingress and many sharp mid-Transit images, I wasn’t  particularly concerned about the seeing. As long as I could see the egress, I’d be a very contented astronomer.

There was something like a black drop effect at Third Contact, but I felt it was mostly the blur and ripple of mediocre seeing. It did give me a hint of what the observers must have felt two and a half centuries ago. Imagine this as your best observation after a year of difficult travel. Not a happy situation!

Venus is just on verge of making Third Contact

Fortunately, my situation in 2012 was considerably happier. I watched, fascinated, as Venus slid past the Sun’s shuddering limb. There wasn’t much agreement as to the instant of Fourth Contact, though the hydrogen-α contingent got an extra half-minute or so.

At length, spontaneous cheers and applause rose from Waikoloa Beach as we acknowledged that the 2012 Transit of Venus was over. We’d been privileged to see a truly rare event, and we’d seen it all.

A splendid conclusion for Transit Day


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About Tim Cole

Astronomy enthusiast and educator, all-around fancier of dark skies and starry nights
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