North Sky

Polaris, the brighest star of the constellation Ursa Minoris located at the tip of the handle of the Little Dipper. As the brightest of all Cepheid Variables, Polaris has been closely monitored in the past by many astronomers. Beginning after 1945, such astronomers noticed a rate of increase in Polaris' period as well as a rate of decrease in it's amplitude. It was then suggested in 1993 that Polaris would cease all pulsations within the next few years. Much to everyone's surprise, in 1998 astronomers noticed that Polaris did not cease pulsating - furthermore, it's amplitude decrease also stopped. With such unpredictable behavior, much is still left to be discoverd about Polaris. The amplitude of Polaris' variations is about 0.03 mag, and it's period is 3.97 days. Some astronomers suspect that we have been witnessing the evolution of Polaris as a Cepheid Variable: that this may be the process by which a Cepheid Variable evolves out of pulsating in it's first overtone to pulsating with its fundamental period - resulting in a more stable and stereotypical Cepheid Variable. This Project seeks to monitor Polaris continuously, providing live images of Polaris and a data base for continuous light curves of Polaris.

We are using a 10 cm refractor and an SBIG STV CCD camera. The field of view is about 5 degrees so the telescope is kept stationary. A specialized computer program was wriiten to control the ccd. The program allows the user to set the exposure time and the interval of time between exposures. The program runs autonomously.

The North Sky telescope is located in the the North Star building of the optical ridge at PARI. The building is equipped with a 24 inch X 26 inch window and is of course oriented due North. Imaging begins when the window shutter is opened and ends when the shutter is closed. Another program monitors weather conditions and opens/closes the shutter at sunset and sunrise, respectively. The images are analyzed using IRAF, resulting in a continuous light curve of Polaris.



Here’s a picture of Dr. Mel Blake, PARI astronomer, and me, next to the North Sky Instrument.

Shown on the right is a the North Sky telescope control panel and  typical image.  Polaris is at the center of the image.


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November 2004. mwc