Saturday, December 12, 2009

Sunset Alignment

Every year it seems I got through the same effort to recalculate the "perfect" dates to catch a particular alignment. From the Mount Lemmon Highway near winter solstice, at the apex of the hairpin turn just past the Thimble Peak Vista pullout, the sun sets behind Kitt Peak National Observatory. An interesting coincidence makes the apparent width of the Observatory just under the apparent width of the sun, so it is perfectly silhouetted. But I've slightly missed it more than I've caught it, so I pour over the images and calculate again what days and exactly where to set up. The image shown here is a "marginal" shot from 2 years ago - if the sun were any further south, the observatory profile wouldn't have fit on the solar image.

I've had a request to lead another "expedition" this year, so I've spent the evening looking up the sun's declination for this year's dates and for past successes. and the results are in! The 2 dates that are in the "perfect" zone are Thursday the 17th, and Friday the 25th. Marginal dates (where you can barely get acceptable results)open up the 16th, 18th and 24th. Moving a few dozen yards can improve the results. I'm offering to lead a group up on the 17th and 25th (yes, Christmas Day), meeting whoever want to join us at the Tanque Verde/Catalina Highway McDonald's at 4pm. There is no delaying departure as sunset is very shortly after 5pm and setup and alignment on the Observatory must be done before the sun comes along! E-mail me by clicking my name at upper right to let me know if you are joining us - in case of questionable weather, I can let you know the go-no go decision if I know you are coming.

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