Astro 11 Laboratory Exercise - Pleiades - Photoelectric...

Photoelectric Photometry of the Pleiades
A Manual to Accompany Software for
the Introductory Astronomy Lab Exercise
Document SM 2: Version 1
Department of Physics
Gettysburg College
Gettysburg, PA 17325
Telephone: [phone]
email: [email protected]
Contemporary Laboratory
Experiences in Astronomy
Student Manual

Contents
Goals .................................................................................................................................................... 3
Objectives ............................................................................................................................................ 3
Equipment ........................................................................................................................................... 4
Introduction ........................................................................................................................................ 4
Operating the Computer Program .................................................................................................... 5
Entering Student Accounting Information ...................................................................................... 6
Accessing the HELP Files .................................................................................................................. 6
Open the Observatory ........................................................................................................................ 6
Telescope and Controls and Readouts (left hand side of photometer) .......................................... 6
Move to a Star ..................................................................................................................................... 8
Set up and Take SKY Readings ......................................................................................................... 9
Take a Reading and Record the Results ........................................................................................... 9
Distance to the Cluster ..................................................................................................................... 10
Extra Credit ...................................................................................................................................... 13

Version 1.0
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AGE
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Goals
You should be able to use photometry to determine the relative apparent and absolute magni-
tude of stars in a cluster in order to calculate the distance to the cluster.
Objectives:
If you learn to .......
Use a simulated photometer to measure the apparent UBV magnitudes of stars.
Make and compare H-R diagrams to find the relationship between absolute and apparent
magnitudes.
You should be able to ......
Determine the distance to a star cluster.

Student Manual
P
AGE
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Equipment
Scientific pocket calculator, graph paper, ruler, plastic transparency, black marker pen, MSDOS Computer with Windows
3.1 (VGA graphics), and CLEA Program Photoelectric Photometry of the Pleiades .
Share the use of the computer and program with your partner to collect data. All calculations and graphing, as well as
your narratives, must be your own original work.
Introduction
The computer program you will use is a realistic simulation of a UBV photometer attached to a moderate sized research
telescope. The telescope is controlled by a computer that allows you to move from star to star and make measurements.
Different filters can be selected for each observation, and the integration time (the length of time the photometer samples
the starlight) is adjustable. The computer also does much of the busy work needed to convert photon counts into apparent
magnitude and provides an estimate of the quality of the collected data.
You will use this instrument to collect data on 24 stars in the region of the Pleiades star cluster. The apparent magnitudes
will be measured for each star, in each of three colors. We will assume all of these stars are approximately the same
distance away . This is a necessary assumption, and reasonable because all of the stars are members of the same cluster.
If we did not make this general assumption, the apparent magnitudes of the stars would also depend on their individual
distances, effect we cannot easily take into account in this lab.
From this information you will plot a Hertzsprung-Russell (H-R) diagram which will display the apparent magnitude of
the cluster of stars as a function of their color index. The color index, B-V, is the apparent blue magnitude (B) minus the
apparent visual magnitude (V). For your H-R diagram, plot the calculated B-V data on the horizontal x axis, and appar-