Existence and archival location of POSSI intermediate glass positives

Ascertain whether the intermediate glass positive plates used to produce the National Geographic Society–Palomar Observatory Sky Survey (POSSI) glass copy negatives still exist, and, if they do, identify their archival location to enable inspection and analysis.

Background

The study highlights the importance of understanding the provenance of POSSI copy materials in evaluating claims of transient sources. Intermediate glass positives were a critical step in the contact-printing process that generated widely distributed copy negatives. Verifying their existence and location would allow direct inspection for emulsion defects and validate the proposed non-astronomical origin of the apparent transients.

While the original POSSI negatives are believed to be archived at the Carnegie Observatories, the authors note that they do not know whether the intermediate positives were retained or where they might be stored, leaving a key piece of the reproduction chain unexamined.