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SSP-4 Photometer Observation Report and Analysis #3 - Color Transformation Coefficients and Airmass Extinction

By Doug West
3 June 2003

In this report I present the equations used in two band photoelectric photometry, determination of the color transformation coefficients, and determination of the extinction coefficients.

The equations used for two band photometry come directly from the book Astronomical Photometry by A. Henden and R. Kaitchuck (1982, Van Nostrand Reinhold Co.).

formulas

Where
J = J band magnitude in the standard system
j = instrumental j band magnitude
H = H band magnitude in the standard system
h = instrumental h band magnitude
kj = principle extinction coefficient
kjh = principle extinction coefficient
= transformation coefficient
= transformation coefficient
ZPj = zero-point constant
ZPjh = zero-point constant

To determine the quantities listed above I used the Henden and Kaitchuck Astronomical Photometry Software For IBM-PC. The J and H magnitudes for the calculations came from the IR Photometry page http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/calib/bright_stds.html.

After four nights of observing the color transformation coefficients became = -.030 +/- 0.004 and = .98 +/- 0.01. The extinction coefficients are kj = 0.10 +/- 0.03 (mags/ unit airmass) and kjh = 0.04 +/- 0.03. As a comparison, the Mauna Kea summit extinction values are kj = 0.114 and kjh = 0.046 (http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/exts.html).

 
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