June 8, 2012

Perforce Employees Gather for the Transit of Venus


The Astronomer: Aimee Ivanoff

Celestial events, such as the transit of Venus across the face of the Sun last Tuesday, are one type of event that brings out the enthusiast in me. Seeing that I don't own a telescope, but a mere digital SLR camera with a 200mm zoom, I could only hope to capture it as it happens. If I'm lucky, I thought, I'll blow up the pictures on my computer screen and view the event after the fact.

It seemed imperative that this event be well attended, given its historical significance. I decided I would goad my fellow Perforcians into dusting off their telescopes and bringing them to share the joy of Venus and Her Waltz with the Sun in the public eye. I braved the public work email list for non-biz emails and sent out the APB. "I'll be in the back parking lot taking pictures of Venus transiting the sun on Tuesday at 3:06pm. Perhaps I'll have some company." And something else in there about anyone having a telescope, maybe they could bring it.

Well this started quite the conversation, and pretty soon, I had two telescope-wielding coworkers committed to hauling their equipment in to the office. One of these kindly denizens was James Creasy. He described his hand-made telescope to me and I was in awe. I told him that he would do well to bring it. Since I was determined to look directly at the sun instead of the projected image, he kindly explained that the power of his telescope pointed directly at the sun and then focused on pretty much anything would set fire to it in a matter of seconds. I was aware of this problem already, and had prepared my own camera with the prescribed filter. But how would we see this directly without burning a hole where it didn't belong?

A Wild Glass Chase

I suggested we go for a quick ride to a welding supply store, not far away, to see if they could outfit us with a Level 14 welding filter. They are 4"x5", and maybe big enough to cover part of the telescope opening. As luck would have it, they were fresh out. Of course "Bob" recommended we stack a #12 and a #5 together and the two of them would give the filter effect we needed. We decided that the several reputable observatories were likely more apt to give sound advice in this department. And they did. Don't stack. On our way back to the car, I commented that if ever there was a time I did not want an earthquake to occur, it would be right then. There were hundreds of free standing gas tanks all around us. Combustion Junction. I was careful when steering around them and out the gate. Onward.

After two more foiled attempts at other welding supply stores in the area, we found that there was a run on the #14 filter. No surprise, given the eclipse a few weeks ago. OK, back to the office. My "lunch" hour was up anyway. For the ensuing hour I was in a meeting. Suffice it to say, when the clock hit 3pm, I literally ran to my desk, grabbed my camera and tripod, and glided down two flights of stairs, not unlike a bowling ball glides into the pins and sends them flying. Considering a recent stair-fall injury, I surprised even myself at how fast I was willing to descend. I landed safely.

venus transit across the sun

There's a Little Black Spot on the Sun Today

Outside I found James, all set up with his absolutely masterful creation, his telescope. Coworkers surrounded him, making oooh, and awww sounds, and what they were seeing was the Sun, and a tiny dot, Venus, at the start of her beautiful Dance, projected onto a large white surface. Not once did anyone want or attempt to have a direct look. We were quite happy seeing it just as it was.

My daughter had shown up with her friend just then after school was out, right on time to enjoy this special event with me. I spent the rest of the hour shooting off my camera, feeling satisfied that I was witness to something so much bigger than I am, and that I was very much a part of it.

The Geeky Stuff: James Creasy

It’s a little hard to see in the picture, but we were projecting an image from the eyepiece of my telescope onto a card. I had designed and built a portable 12.5” aperture, f/6 Dobsonian reflecting telescope some years ago for nighttime viewing of stars, comets, galaxies, planets and nebulae. To convert this large a scope for solar viewing requires stopping down the light to a 2 inch diameter circle; otherwise the heat of the light could melt or set on fire bystanders or the telescope itself. “Necessity is the mother of invention”, and so the few minutes before the transit started found me punching the bottom out of a paper cup and wedging it into a paper bowl before taping it around the hole of an LP record slipcover, itself covered with aluminum foil! You can see this ungainly contraption on the top of the telescope in the picture.

The Telescope

I received quite a few questions about my telescope, and I’ll answer some here. I had previously built a smaller, fairly standard scope with a fixed tube. It performs well, but when I got interested in a bigger scope around 1990 I realized I need more portability. The best viewing is at remote, isolated sites, and so the telescope needs to fit in an ordinary car for transport and be light enough to carry to the viewing site from the car.  My solution was a collapsible Serrurier-truss style scope, where the tubes of the truss can be easily removed. The box at the top which houses the diagonal mirror fits inside the main mirror box, which then all fits in the seat of a normal car. The 8 aluminum tubes are then bundled together. Setup is about 5 minutes, take down, 2. The main mirror is a 2 inch thick piece of Pyrex, 12.5 inches in diameter, with a focal length of 1224mm for a focal ratio of f/6.  I picked this because a tall ladder is not needed to reach the eyepiece; even at zenith a step ladder will do. The secondary mirror is unusually small at 1.83 inches diameter as I was able to position the eyepiece holder just outside the light path, where the light cone is biggest. Optimizing the coverage for visual viewing only (not larger 35mm film) also allowed reduction of the size. A small secondary mirror allows more light to reach the eyepiece, but more importantly, reduces the blurring effects of diffraction caused by an obstruction in the light path.

Remember Calculators?

Looking back, I’m struck by how much harder and slower this all was before the Internet. All the design was painstakingly done with paper and pencil, the calculation with a hand-held calculator, and the information found in a book or looked up at a library.

Thanks, Perforce!

One thing that’s remained the same over the years is my enjoyment seeing people captivated by a first-hand glimpse at our universe. Sure, these days you might get a better picture online, but that misses the intimate immediacy of viewing actual photons emitted from the sun, some blocked by Venus in a tiny-yet-huge spot. It was a pleasure to have the opportunity to share this with my co-workers here at Perforce, and thanks to my co-author, Aimee Ivanoff, for inspiring me to dust off the old contraption and drag it into the office last Tuesday!

Photo credits: Aimee Ivanoff and James Creasy