Friday, June 1, 2012

Transit Practice

With excitement for the coming Venus transit this coming Tuesday (June 5) I ordered me up a Canon Extender EF 2X III to double the focal length of the 200mm lens.  As I learned from the annular eclipse the image scale (for the sun) with the 200mm is pretty meager.

I took the following picture yesterday and while the sun still doesn't fill much of the frame it is more than  adequate for my transit purposes.  All I really want is a record of having lived through it and if all goes well assemble an image sequence into a movie.

Here is the full frame with the T2i.

Ol' Sol

I took that image, brought it into Pixinsight for enhancement and colorization.  Here is the result after a heavy crop.

Detail visible after processing in Pixinsight.  Please click for larger size - it's much nicer.

Focusing is a challenge ... in full daylight it is difficult to see the camera screen.  Autofocus does work but I'm not absolutely certain if I could improve on that with manual focus or not.  The above was focused manually using the buttons on the control box for the robofocus.  While it was the best of the lot it a moment of good seeing could easily account for the improvement.

Taken in my backyard in San Jose, CA  May 31, 2012
Canon T2i (stock), Canon EF 200mm f/2.8L + Extender EF 2X III @ f8

Baader solar film over lens cap
AP900 mount
1/640 sec exposure @ ISO100
post-processed in PixInsight


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  2. I'll be projecting through my 80mm refractor. I'd recommend testing it first so you don't fry at transit time. If you have an issue of course you could always make a aperture mask. With that much light you should be have a huge bright image.