AstroDrizzle: Aperture Photometry Accuracy
The goal of this demonstration is to assert the accuracy of aperture photometry measurements on ACS/WFC images using the new software package Drizzlepac. With this goal in mind, we compare stellar instrumental magnitudes calculated using individual FLT images from the HST pipeline with the instrumental magnitudes of the same sources estimated using the AstroDrizzle output.
Observational dataThis example describes the combination of two sets of three ACS/WFC images of open cluster NGC 6791 (Program 9815, PI Ivan King) which were obtained with the filters F606W and F814W. The GO used three orbit visit for each filter, taking three short (30 sec) exposures with POS TARGS in order to achieve a 3-way sub-pixel dither pattern. The interchip gap was not covered in these observations. Table 1 provides some basic information on the images which are available from the HST archive for those who wish to repeat this experiment.
Table 1: HST/ACS datasets used in our experiment. The exposure time is given in seconds.