Prepping for the upcoming transit of Venus…

June 2, 2012 | Astronomy | By: Mark VandeWettering

I’ve been pretty quiet on the blog, but I’m trying to get some projects going. This week marks a rather rare event: the Tuesday (for us in North America) transit of Venus across the front of the sun. According to this transit calculator, the transit will occur between 3:06 and 9:47 (well after sunset).

Back on Nov 15, 1999, I observed a transit of the planet Mercury across the sun. I snapped a few pictures, and created this rather unimpressive animated GIF:

Nov. 15, 1999 transit of Mercury in front of the sun

I don’t even recall what crude webcam setup I had back then.

I think that I can do better this time. You may have seen my “ghetto” astrophotographs of the solar eclipse a couple of weeks ago. I shot those using a solar filter over my little Meade Maksutov. I though I’d press it into service again, but instead of doing the crazy “catch as you can” approach of clicking away with a hand held point and shoot at the eyepiece, I thought I’d dig up something better.

Better in this case was an old black and white security camera that I had bought from Supercircuits years ago with the idea of doing some video astronomy. I even modified the camera to allow the disabling of its automatic gain circuitry, which typically is useless for astronomy, as it causes the camera to overexpose everything you wish to see. More digging found the other necessary bits (various camera adapters and the like). I wanted to capture images to my laptop, so I needed a little Video->USB capture card. A quick trip to Fry’s netted me a MyGico Capit card for the princely sum of $20, with a $15 rebate. It took me a couple of tries to get the drivers installed, but it seemed to work okay. I then aimed my rig out the window up my hill, and shot this picture of the fencepost at the back of my property:

My fencepost, viewed through the Maksutov/Video Camera setup

The focus wasn’t perfect, but I could actually see an ant crawling around on it. Not bad. Not bad at all.

Except for one thing. The distance to the post is about 135 feet, and the post is a 4×4. A little math works out the field of view of this camera as being roughly .2 degrees. The sun is roughly one half a degree in size. This means that whatever I do, I won’t get a full disk image of the sun. That’s kind of a bummer.

Of course, I could have made a math error. I’ll drag this rig out into the sunshine and see if I can shoot some pictures/vids of the sun today (should see some sunspots anyway) and see how close my math is.

I’ll try to shoot some Youtube video that will further document this setup later. Stay tuned.

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