“If you can’t measure something, you can’t understand it. If you can’t understand it, you can’t control it. If you can’t control it, you can’t improve it.” -H. James Harrington
If you want to observe the night sky, it’s not quite as simple as pointing your telescope and collecting photons. You have to calibrate your data, otherwise your interpretation of what you’re looking at could be skewed by gas, dust, the atmosphere or other intervening factors that you’ve failed to consider. Without a proper calibration, you don’t know how reliable what you’re looking at is.
The previous best calibration was the Digitized Sky Survey 2, which went down to 13 millimagnitudes, or an accuracy of 1.2%. Just a few weeks ago, Pan-STARRS released the largest astronomy survey results of all-time: 2 Petabytes of data. It quadruples the accuracy of every calibration we’ve ever had, and that’s before you even get into the phenomenal science it’s uncovered.