The guide star is in the 2MASS
catalog with a K magnitude of 11.374 in the Vega system. For the
K-prime filter, the correction to AB is 1.834 magnitudes, so the star
has K_AB=13.21. Because the central pixels of image of the star are
saturated, we must interpolate from the wings to find the total flux.
The figure at right shows the radial profile of the star the black
points indicate the saturated pixels. The red points indicate points in the fitting
radius and the scattered blue
points indicate points outside the fitting radius. The
green line indicates the fitting
function, a Lorentzian. Within the fitting radius, the data is superceded
by the fit, as indicated by the unscattered blue points.
The best fit zero-point is 30.02, althought the details of the fitting
process could change this by a few tenths of a magnitude.
The IRAF photometry package was used to get magnitudes for the other
objects in the frame. When measured through a 0.3 arcsecond (14 pixel)
aperture radius we find:
|Galaxy||K_AB ||Err |