Wednesday, June 6, 2012

Venus Transit w/a Few Friends!

Yesterday (Tuesday the 5th), was the big Venus transit.  Of course, there was one just 8 years ago, but visible only in Asia and Europe - not visible in the US except for along the eastern seaboard for about an hour at sunrise.  The next one isn't until 2117, yep - that's right, 105.5 years!  So, I'm thinking I might not make it to the next one, so needed to get organized and take a look at this one.  The big question was should I go off somewhere on my own to take pictures, or share the view with friends?  Anyone who knows me should know that answer - go where you can find the biggest crowds and share the view! 

Transits of the inner planets are rare things.  They also play historical and important roles in science.  Transits of Venus were particularly important in defining the scale of the solar system.  In the 18th century, we knew the distance to the planets, not in miles, but in units of the distance from Earth to the Sun.  Only by using parallax methods, observing a Venus transit from widely spaced points on our planet and noting the subtle differences, could we triangulate the distance to Venus in miles, and thus the absolute scale of the solar system.  There is a rip-roaring tale of adventure that Captain James Cook took to Tahiti for the 1769 transit at this NASA site.  The voyage took nearly 3 years, and 40% of the crew died - deemed acceptable losses for such a voyage in those days.  I highly recommend reading the account - certainly worthy of a modern documentary or movie treatment!

I did want to try to image it, as well as set up some scopes for the public.  The imaging setup consisted of my workhorse G-11 mount with a 7" apochromatic refractor built by Roger Ceragioli about 10 years ago. It is an excellent little telescope, and a perfect focal length for imaging fields smaller than the sun's diameter.  Unfortunately, the public nearly always demands that anything set up before them needs to be looked through.  It took nearly constant attention to keep folks from hanging off the photographic setup, even though there was clearly a camera clicking away every 20 seconds...    In one attention lapse, someone who had watched me adjust the scope looking through the little guide scope, did the same and while I patiently checked after him, the sun was completely out of the field!  Should have set up traffic cones and barbed wire!  I did have 3 other devices set up for them - my "big" 20X120 Japanese battleship binoculars, a little Meade 80mm apo refractor, and a "Sunspotter II" folded telescope that safely projects an image of the sun onto a screen.  The image at left shows workmate Kirk and Janet mugging for the camera over the Sunspotter II projector.

With all that gear to set up, including a borrowed canopy to provide just a little relief from the unrelenting Arizona sun (projected high of 100F), I was the first to arrive at 12:30 for the 1500 transit start.  Securing a mall parking pass, I got to work.  Unfortunately they had chosen that morning to apply steer manure fertilizer to the mall, and early on the flies were bothersome - but hey, I'm a farmboy, so toughed through it!  I started setting up the tracking mount, then the first camerawoman came by, wanting to see part of the setup, so after she set up her tripod and I cued her to start, I carried out the big binoculars and plopped them on the mount - nearly a third her diminutive stature, she was impressed!  I put on the solar filters, but it was nearly high noon with sun overhead, it was uncomfortable to look so high in the sky...  I alternated with other scope setup, then the canopy.  Other amateur astronomers arrived, then the public, then, as if sniffing out a story, the press came for the live early news coverage.  Besides the early encounter with the channel 4 correspondent, I was live on channel 9,getting to talk a bit about the binoculars, and I also had an NPR crew interviewing me for an upcoming radio program.  Image at left is of "second contact", when the full disk of Venus first fully enters the disk of the sun.  Roger's scope was used at 1/4000 second for most of the transit images.


Of course, by that time the transit was well under way.  I had finished my setup with minutes to spare, and Melinda had come down early to help setup and run a telescope.  With 2 other volunteers assisting, I got to focus on getting the camera system going and not deal with the public early on.  Right on schedule (funny how that happens!), the startlingly big disk of Venus inched into the sun's disk.  One of the things I was looking to record was the atmosphere of Venus refracting a ring of light before it fully came into the sun.  I never saw it, but took a couple frames with slightly longer exposures to try to capture the "aureole" of Venus.  Hours later, once loaded into the computer, by stretching the contrast beyond the limits of common sense, it appears to be barely visible - cool!

During the bulk of the transit we had some huge crowds - I was guessing over a thousand, but I heard some estimates of 3,000!  Of course, setting up in "astronomy central", within a block of Steward Observatory, Lunar and Planetary Labs, National Optical Astronomy Observatories, Optical Sciences and the Mirror Lab, it seems I knew or recognised a good percentage of the people who came by.  The big binoculars were VERY popular, sporting some of the longest lines.  It's 20 power 3 degree field is almost the perfect complement to viewing something the size of the sun or moon.  Believe it or not, I also got a very strong 3-D effect of Venus floating in front of the sun - impossible, of course, because of the great distances involved, but strong nonetheless!  Note the picture here of mom helping her son view - daughter is preparing, getting her fingers nice and sticky with candy before she gets to reach for the eyepieces!  I saw and caught her in time to prevent a sticky mess, though I was busy a good part of the afternoon on mascara patrol, keeping the eye lenses clear of that contaminant!

There were a lot of telescopes there, 40 by some counts, and it wasn't till the crowd started to wane that I got to walk around and say hi to anyone.  One of the more unusual setups  was by Tucson Amateur Astronomy Association (TAAA) member Debra, who had set up her "light bucket" telescope.  For those who don't trust solar filters (and there were quite a number who don't), Debra fastens an actual bucket to the back of her Schmidt Cassegrain telescope, and projects the sun onto what looks like a translucent screen made of shower curtain!  The image was sharp, large and bright, and was a great way to safely view the transit, as shown here. 

The Sunspotter II that I had setup attracted some attention too.  I originally saw the first models at Texas Star Party or Riverside Telescope Makers Conference a couple decades ago, and ordered mine.  They are numbered and dated, mine being made in June of 1991, so is well over a couple decades old.  Mine uses a simple singlet long-focus lens, the beam of which is folded around the interior of the triangular solid before being diverted downwards through an eyepiece where the sun's image is projected onto a screen.  There was also a current version of the Sunspotter, first mounted on a tabletop (where it is designed to be used), but I didn't get to it until it had been placed on the ground.  The current model is much improved - my older version (visible in the top picture with Kirk and Janet above) has no mount at all, but in this case I attached it to a tracking mount.  The new version has a very smooth looking alt-azimuth tabletop mount that looks exceedingly easy to use and point.  It also sports a larger diameter achromatic lens and improved eyepiece that gives a larger sharper image than my model II.  However, most Internet prices have them at $400, while I recall the price I paid in 1991 being $50 or $60.  The price of progress and a better product...

Once the transit was well underway, time seemed to fly by.  I had lots of people come back and repeat looks through the binoculars, telling me they were the best view there.  Finally the sun dropped below the Modern Languages building, which I've got a couple frames of!  Once the sun was gone, the people left and we packed up, and rushed off to our next appointment - a tour of the Mirror Lab for the NPR crew, and eventually dinner with friends at The Crossroads Mexican restaurant in South Tucson.  It took about 2 pitchers of water and a couple beers to hydrate everyone, and we were stuffed by the time we headed home at 2130 to a house of hungry cats (4 hours past their normal feeding time!).  But the transit was a spectacular event, and the celebration on the UA mall was a great success.  The last image shown here is very near mid-transit, though after looking at all these pictures that I and others have taken, they start to all look the same!  I think we inspired some kids as well as parents, and seeing that always invigorates me, convinced that doing public astronomy is just about the best use of telescopes - inspiring others.

3 comments:

David A. Harvey said...

Nice post about the transit - and great pics! I must acquire one of those new Sunspotters - pretty cool.

Alan said...

Great write up Dean! Looks like it was a blast!

David Oesper said...

Hi Dean,

The best view anyone had of the Transit of Venus at the McDonald Observatory Visitors Center was through your 15 x 70 Fujinon binoculars with two AstroZap solar filters we purchased. The view was astounding! This same combo was a big hit at the Annular Solar Eclipse, too!

Thanks so much!

Dave