Transcript Photometric Data Collection At The Burke Gaffney Observatory

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