Cleaning the USNO-B Catalog through automatic detection of optical artifacts

TL;DR

This paper presents an automated computer vision method to identify and remove spurious entries caused by optical artifacts in the USNO-B star catalog, improving its reliability for scientific use.

Contribution

The authors develop and apply novel Hough transform-based techniques to detect diffraction spikes and reflection halos, significantly reducing false entries in the catalog.

Findings

Identified over 24 million spurious entries caused by diffraction spikes.

Detected nearly 200,000 spurious entries from reflection halos.

Method effectively distinguishes artifacts without relying on photometric outlier detection.

Abstract

The USNO-B Catalog contains spurious entries that are caused by diffraction spikes and circular reflection halos around bright stars in the original imaging data. These spurious entries appear in the Catalog as if they were real stars; they are confusing for some scientific tasks. The spurious entries can be identified by simple computer vision techniques because they produce repeatable patterns on the sky. Some techniques employed here are variants of the Hough transform, one of which is sensitive to (two-dimensional) overdensities of faint stars in thin right-angle cross patterns centered on bright ($<13 \mag$) stars, and one of which is sensitive to thin annular overdensities centered on very bright ($<7 \mag$) stars. After enforcing conservative statistical requirements on spurious-entry identifications, we find that of the 1,042,618,261 entries in the USNO-B Catalog, 24,148,382 of them ($2.3 \percent$) are identified as spurious by diffraction-spike criteria and 196,133 ($0.02 \percent$) are identified as spurious by reflection-halo criteria. The spurious entries are often detected in more than 2 bands and are not overwhelmingly outliers in any photometric properties; they therefore cannot be rejected easily on other grounds, i.e., without the use of computer vision techniques. We demonstrate our method, and return to the community in electronic form a table of spurious entries in the Catalog.