I'm wondering whether anyone can suggest a tool for this user case problem: I have time series data for small patches of the sky. There are several pointings with different exposure times, etc. I would like to make a plot with the cumulative exptime coverage of the field I'm looking at. What is the best tool to do that? I feel that my current idea is rather brute force, only slightly better than stacking all the images (a few thousand) together with exptime instead of flux data.