User's Guide Contents
	Return to ETC Welcome SYNPHOT SNR and Exposure Time SNR Time Optimal SNR Spectroscopy Target Acquisition Basic Use Page Heirarchy Reference Extraction Regions Spectral Distribution User Spectra Other Spectra Extinction Normalization Background CCD Parameters ID Number Calculations SYNPHOT Calls Call Descriptions Call Parameters NICMOS Spectroscopic Extraction Regions Tables Spectral Elements NICMOS Filters NICMOS Dispersers ACS Filters and Dispersers COS Dispersers WFC3 Filters and Dispersers STIS Filters and Dispersers NICMOS Tables COS Tables STIS Tables and Topical Help

# Frames

Here the user can specify the number of distinct frames (exposures)  comprising their observation. 

This is analogous to the "CR-SPLIT"  parameter that was popular in the early days of HST, but today has  been supplanted by distinct exposures taken in tandem with  dithering, allowing not only the rejection of cosmic rays but also  the masking of detector artifacts and a resampling of the point  spread function.