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

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.).

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
• k_j = principle extinction coefficient
• k_jh = principle extinction coefficient
• = transformation coefficient
• = transformation coefficient
• ZP_j = zero-point constant
• ZP_jh = 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 k_j = 0.10 +/- 0.03 (mags/ unit airmass) and k_jh = 0.04 +/- 0.03. As a comparison, the Mauna Kea summit extinction values are k_j = 0.114 and k_jh = 0.046 (http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/exts.html).