Welcome to the Exposure Time Calculator (ETC)
FOR THE CURRENT ETC (ETC 20.1) USER'S GUIDE, GO HERE.
User Guides for older versions have be found here:
ETC 19.1 and previous versions' links
The ETC is a web-based application developed in Java that assists Hubble astronomers and engineers in preparing Phase I and Phase II observing proposals for submission to the Space Telescope Science Institute (STSci). The ETC’s sole purpose is to calculate the following:
Signal-To-Noise (SNR) Ratio (for a given Exposure Time)
Exposure Time (given a desired SNR Ratio)