Origin of nonrandom intra-plate SPF patterns

Identify and characterize the generative processes responsible for nonrandom intra-plate spatial patterns of Selected POSS1-E Features (SPFs), including clusters bounded by geometric shapes, voids, stripes, and edge concentrations, and determine whether these patterns arise from plate manufacture, handling, degradation, digitization, or data processing.

Background

The authors present examples where SPFs cluster within regions with clear geometric boundaries and exhibit voids or band-like gaps, often related to plate edges or the celestial coordinate grid.

They hypothesize that templating by contact or preferential exposure could be responsible, but explicitly state that the origin of these patterns is not known, indicating a need for investigation of plate and processing mechanisms.

References

A prominent example occurs very near the celestial meridian and equator in the plate with the largest number of SPFs (Plate 090R; N = 2,149; part A in Figure 1), where the majority of SPFs are located between the boundaries of the plate and an oval that is partially inscribed within it. The origin of these patterns is not known.

— Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates  (2601.21946 - Watters et al., 29 Jan 2026) in Section 4.3