Instrument Science Report WFPC2 97-08:
New Results on Charge Transfer Efficiency and Constraints on Flat-Field Accuracy
B. Whitmore and I. Heyer
September 04, 1997
The primary new results based on observations from calibration proposal 6195 are:
1. A set of new formulae has been developed to correct for CTE loss, with dependencies on the X and Y positions, the background counts, and the brightness of the star. The use of this formula reduces the observational scatter in this particular dataset from 4-7% to 2-3%, depending on the filter.
2. A small correction is required to normalize results from aperture photometry on the three WF chips. This normalization can be understood as the product of different aperture corrections (i.e., variations in the PSF) and different gain ratios for the three chips.
3. The uncertainties in aperture photometry of point sources due to flat-fields are less than (probably considerably less than) 1.5% across the chip and 0.6% chip-to-chip.