Venus Transit Retro-Blog: Transit Day, Part 1

2012 June 05 — The day of the 2012 Transit of Venus

Oddly enough for me, I was up at dawn that morning. As I’d posted that morning, the weather seemed to be cooperating. Certainly the view from my hotel balcony was encouraging.

Observers fill the VIS parking lot, waiting for the Transit of Venus to start. The gabled building behind the canopy is part of the staff residence complex

Our Sky and Telescope Transit of Venus group traveled to the Visitor Information Station (the “VIS”) on Mauna Kea in nine separate vans. By 10:30 my van arrived at the VIS. Parking was already becoming a problem, but our group’s “headquarters” area was outside the staff residence complex for the observatories. That’s just a short distance uphill from the VIS, so there was plenty of time to find a spot and set up.

At 9200 feet, we’re well above the cloud deck

The VIS is 9200 feet above sea level. At that altitude, the air pressure is about 73% of its sea level value. Getting out of the van, just walking took more effort than I’d imagined, even though I’d known what to expect. Some things have to be experienced — thinking it through just doesn’t quite do it.

Preparation does help, though. I’d been advised to walk slowly and to pay attention to breathing deeply.  It worked well, and I soon found that I hardly noticed the thinner air. Most of the time, anyway. Walking uphill from the VIS reminded me where I was. Pride cometh before the gasping wheeze!

By noon, most people I could see were either peering through their own telescopes or binoculars, or clustered around the public telescopes with projection viewers. There was a strong, somewhat gusty wind that jostled my telescope, but the Sun’s image was crisp, with a sharp limb and vivid sunspots.

Observers using hydrogen-α filters could see Venus move in front of the Sun’s chromosphere, invisible to white-light observers like me. It gave us a bit of advance notice of First Contact — about half a minute, as it turned out.

My first view of the 2012 Venus Transit was a tiny notch in the Sun’s limb. Over the next dozen minutes, I watched as Venus slowly moved into the Sun’s disc. When Venus was perhaps 80% of the way across the Sun’s limb, I saw a faint grey edge around the “space side” of Venus. It wavered, and didn’t form a complete circular arc, but I’m certain I saw the famous aureole of Venus.

Just before Second Contact, I looked carefully for infamous black drop effect. I didn’t see anything like the threads and tear-drops described in journals from the 1761 and 1769 expeditions, but I noticed some faint blurring of the trailing edge of Venus as it moved across the limb. Judging by comments from nearby observers, most of us saw only mild versions of the black drop effect.

The Sun before and after Venus’s ingress

By 12:30, Venus had completely crossed the limb, and I got a few photos for keepsakes. This was a great time to wander around the observing area, look at projected images of the Sun and Venus, take a few peeks through other ‘scopes, and generally share the experience with other astronomers. For the next few hours, I took the opportunity to mingle, see terrestrial sights, and take frequent peeks at Venus crossing the Sun.

You can find more photos from Transit Day here.

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About Tim Cole

Astronomy enthusiast and educator, all-around fancier of dark skies and starry nights
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One Response to Venus Transit Retro-Blog: Transit Day, Part 1

  1. Pingback: Venus Transit Retro-Blog: Keck Observatory HQ | Sidereal Moments

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