by Rex Parker, PhD director@princetonastronomy.org 

Peyton Hall and Beyond. Our journey through the universe and university continues in December as we meet for the last time (for a while, anyway) in Peyton Hall, which will undergo renovation in 2015. This will lead us to different campus venues beginning in January (Green Hall) as we adapt to the changes. Stay tuned to Sidereal Times for updates on upcoming meetings as we enter a new phase of club activities.

Solstice – Solar and Clock time. Soon the sun will reach its most southerly apparent position as the temperatures drop and the days shorten. Solstice comes on December 21, formally beginning winter season in the northern hemisphere. The solstice brings the shortest day and longest night of the year, but surprisingly it is not the earliest sunset for us in New Jersey, which will occur December 7. This seeming paradox may need some explaining. The answer has more to do with clocks than celestial mechanics, because our time system is based only approximately on solar days. Clocks are based on exactly 24.0 hour days, while a solar day (the period between solar transits) varies and is seldom 24.0 hours. In December, one solar noon to the next is about 24 hours plus half a minute. So the sun reaches its noontime (southernmost) position about seven minutes earlier on December 7th than the 21st. The exact relationship between apparent solar (sundial) time and clock time is more complex, as shown in the graph below, which shows the equation of time — above the axis the sundial is faster than the clock, and below the axis it is slower.  

The Equation of Time Credit: U.S. Naval Observatory

Starstruck. One of the first-ever major exhibitions revealing astrophotography in all its glory as a genre of the fine arts is now running at the Michener Museum in Doylestown, PA. This exhibition features over 100 printed images from 35 astronomer-artists from around the world. The celestial show includes several images from AAAP’s speaker from last month, Dr Steven Mazlin, as well as many other nationally-known experts in the field. The photographs in this exhibition were selected by a distinguished group including Dennis di Cicco of Sky and Telescope and J.T. Bonnell of NASA’s APOD. Your opportunity to see this amazing show in Doylestown, PA will extend through Feb 8, 2015. I was personally starstruck after viewing the exhibit, the most impressive and inspiring astrophotography I’ve ever seen.

Winter and the heavens. Contemplate the splendor and wonder of the night sky as you button up and pull on your gloves. Wishing all members well as we wrap up a year of fine astronomy in AAAP.