While taking data on the stars you need only record their names which can be their right ascension and declination and their B and V magnitudes. U magnitudes are not used in the analysis so please do not take U magnitudes unless you just enjoy doing extra work for no purpose. This data table of names, B, V, and B-V (which you compute via subtraction) will be one of the things you turn in.
This is a big hint, if the Mean Sky box says NO SKY! you have not
taken a NO SKY reading yet. You will not get a B or V until you read
the sky, that means someplace without an obvious star. You need to read
a place
with no star so that the light there can be subtracted from what it is
when
you are on a star. You will not get a Magnitude reading until you read
the EMPTY SKY with both the B and V filter. You will then be able to
get
reading of B and V on stars.
CLEApho.xls has the ZAMS calibration graph already inputted whose data is on page 11 of the "Photoelectric Photometry of the Pleiades Manual above" and another graph set up for you to input your (B-V,V), color versus apparent visual magnitude, ordered pairs from the photometry of the stars you have measured. You may have to save this file and then open it in Excel. You will have to print out both graphs on the same printer to the same scale.
You should also turn in the graph of the zero age main sequence absolute magnitudes versus B-V; and the graph of your data of apparent V versus B-V. It is important that both graphs have the same numerical scale on both x and y and that they be printed on the same printer at the same scale since you are going to visually superimpose them on top of each other to get the difference between apparent and absolute magnitude. This distance modulus, m-M, the difference between apparent, m, and absolute magnitude, M, will be use in the formulae to get the distance to the Pleiades cluster in parsecs. d(pc)=10*10^((m-M)/5) . Then take the distance in parsecs and convert it to light years by using the conversion factor 3.26 Light year is equal to 1 parsec. Then compare the distance in light years to that accepted value of 410 light years and this will be your present difference.
Suppose that your distance modulus, m-M was 5, it won't be or at least shouldn't be this. Using the formulae d(pc)=10*10^(5/5)=100 parsecs. 100 parsecs x 3.26 light years/1 parsec = 326 light years. Comparing this to 410 light years for a present difference yields (410-326)/410*100=20.49%.
Suppose that your distance modulus, m-M was 6, it won't be or at least shouldn't be this. Using the formulae d(pc)=10*10^(6/5)=158.49 parsecs. 158.49 parsecs x 3.26 light years/1 parsec = 516.68 light years. Comparing this to 410 light years for a present difference yields (410-516)/410*100=-25.85%.
Your distance modulus from the interpolation of the two graphs
keeping color the same will be something between 5 and 6. Your
percentage differences will be much smaller than my examples of 20.49%
and -25.85%.
Last changed by Dr. Harold Williams, 3:02PM, May 5, 2011