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Download Photometric Data Collection At The Burke Gaffney Observatory
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Photometric Data Collection At The Burke Gaffney Observatory By Jayme Derrah Overview • Photometry At The BGO • The Photometer • Collecting Data • Extinction • Polaris • Results • Problems Encountered Photometry At The BGO • No one has done this at the BGO for years • Collect data in hopes of finding extinction coefficients for Halifax skies. • No other observations in Halifax to compare with • Collect data on several Cepheid Variable stars, including Polaris The Photometer • Optec SSP-3 Photometer • Works like a 1 pixel CCD • Measures apparent brightness of the object in question Collecting Data • Take readings in the blue, visual and ultraviolet ends of the spectrum • Most readings on the sky are dominated by noise in the uncooled photometer • Need to collect data on standard stars at different air masses • For variable stars, a nearby reference star is needed Data • Use the apparent brightness readings to determine the apparent magnitude of the object using the equation: m1-m2= 2.5*log(b1/b2) Extinction • Produced by haze, clouds, fog, which cause changes in sky transparency • Greater extinction at larger distances from zenith • The greater the air mass, the more light that is absorbed . • With accurate extinction coefficients, can standardize data collected on stars, such as Polaris Extinction (continued) • To determine accurate extinction coefficients, need readings on many different standard stars observed at a variety of air masses k'y = 0.213 (0.13-0.16 at 7000 ft) k"y = -0.025 (0.00 at 7000 ft) k'by = 0.154 (0.10-0.13 at 7000 ft) k"by = -0.033 (same at 7000 ft) k'ub = 0.281 (0.21-0.25 at 7000 ft) Polaris • Polaris is the closest and brightest Cepheid Variable star to us • Cepheids are variable stars whose luminosities are proportional to their periods • Polaris has a period of about four days • Its period is slowly increasing, and it may soon stop pulsating since its amplitude is decreasing • Not many observations done on it for years • The air mass around Polaris stays relatively constant, so it is good to observe at the BGO Results • Light curve from last summer: Problems Encountered • Transparency changes throughout the night • Thin cirrus clouds often difficult to detect • Tightening the clamps on the telescope • Aligning the telescope • Finding Polaris and the stars in its field Thank You • Special thanks to Dr. David Turner
