Two of the tests to determine which candidates were real: the size of the fitted major axis relative to the PSF (horizontal axis) and the error in position from the fit (vertical axis). The black lines show the test thresholds: 1.2 times the fitted major axis size and 0.04 pixels position error. Each point is a candidate peak, colored by how it was evaluated by the tests (positives passed all tests, negatives failed one or more tests, including the tests not shown) and the manual inspection (true positives/negatives where the tests match the manual inspection, false where the tests do not match the manual inspection).