The Transit of Venus - June 5, 2012 (Mountain Standard Time)

Photographs by David Shaffer

Ingress  and  Second contact -- I took pictures every minute during ingress, from first contact to a minute before second contact (when Venus first becomes totally within the solar image).  You can see Venus becoming more and more obvious.  Then, I took a frame every two seconds for two minutes centered on the predicted time of second contact.  The image at predicted second contact (4086) shows Venus well within the Sun, but a little imagination helps to convince yourself that second contact has happened (envision a circle fit to Venus).  Another frame (4096), some 20 seconds later, is more convincing.  The intervening frames show the "black drop effect" which bedeviled early studies of Venus's transits (look at 4094, where the teardrop necking from Venus to the exterior of the Sun is obvious).  The second contact frames have been brightened slightly but no contrast enhancement has been applied - that makes Venus tend to blend in with the rim of the Sun.

Here are some of the pictures I took during the transit of Venus, as observed from Flagstaff, Arizona on the afternoon of June 5, 2012 (local time - note that Arizona does not observe Daylight Savings time, so that any and all times noted herein are Mountain Standard Time).  The actual location from which the pictures were taken is northwest of Flagstaff, in an area known locally as Baderville.  The corresponding longitude and latitude are  111.7426 degrees (west) and  35.2620 degree (north), as read from DeLorme Mapping's Topo North America 9.  Errors on these values should be at or below +/-0.001 degree.  All times should be accurate to 1 second or better - I set my wristwatch to USNO time, and took pictures of my watch with my camera before and after the transit to calibrate the camera time, which is included in the metadata for each camera frame.

These pictures were taken with a Pentax K5D camera, on a (somewhat crudely aligned) tracking polar mount.  The orientation of each frame has celestial north "up."  (Near sunset, this means the camera is nearly on its side, hence the pine trees entering the frame from the right, not the bottom!  See the picture on the right.)  I used a Pentax 300mm lens with both a Kenko 1.5x and 2x teleconverter attached to the camera, resulting in an optical focal length of 900mm for the lens, and an effective focal length of 1350mm (35mm film camera equivalent, due to the 1.5x crop factor of the Pentax camera sensor).  A neutral density 3.0 filter (transmittance of 0.001) was attached to the front of the lens.  The filter (about 10 stops) and the teleconverters (about 3 stops total) reduced the sun's light to a tolerable level for the camera.  Exposure times for all frames were 1/2500 sec, at f11 aperture.  The images shown here have been processed in Photoshop Elements 9, to trim the solar image (resulting in a bit of "bounce" of the position from frame to frame), enhance the contrast, and brighten the image.  The trimmed images are 1500 pixels square.  The sun is about 30 arcminutes (1800 arcseconds) across, so each pixel is somewhat bigger than an arcescond square.  At this level, sunspots are readily visible in all frames, and the effects of seeing are obvious.  It was a warm, breezy day during the transit.  

Time tags and (sometimes) minor commentary have been added to each image.If you would prefer an original file, please send me an email:   shaffer@alumni.caltech.edu

The various albums were created with the program Jalbum.  Once you are in a particular album, you can navigate around by clicking on a thumbnail image, which will bring up a mid-size version of that picture.  By clicking at one side or the other within a mid-size image, you can go forward or backwards in the album.  If you click near the top of a mid-size image (within the frame), you will go back to the set of thumbnail images.  If you click in, but near the bottom, of a mid-size frame, you will get a full size (1500x1500 pixel) image.  Clicking anywhere within the full-size image takes you back to the corresponding mid-size image .

First contact: I took pictures every two seconds during a two minute interval centered on predicted first contact (when Venus first appears to be covering up some part of the Sun).  Turns out, you pretty much can't recognize first contact - Venus is just barely doing anything!  The first frame in which I am convinced I can see Venus is some 45 seconds after predicted first contact - when Venus is around 2.5 arcseconds onto the Sun - and that's in large part because I knew where to look.  I don't show any images from this set.  All predicted times come from a transit circular issued for Flagstaff by the Coconino Astronomical Society.  The predictions therein closely match those from the website maintained by Fred Espenak of NASA at http://eclipse.gsfc.nasa.gov/transit/transit.html and references therein.

Transit  -- I took a picture about 1 1/2 minutes after second contact (at 15:25 MST) and then a picture every ten minutes, on the 10 minutes (i.e. 15:30 MST, 15:40 MST, ...) for the rest of the transit, until almost local sunset, when Venus disappeared behind the trees about 300 feet from where I was set up.  There is one extra frame at 18:25, the time of Venus's nearest approach to the center of the Sun.