Grouping repeated exposures produces a strong field identification. Too few unused reference associations remain for a trustworthy independent distortion fit.
The primary sky solution centers on α Geminorum (Castor). A roughly 59-pixel repeated-image family has reference support in that field; a roughly 44-pixel family has not been assigned to it. Bounded searches around tentative Monoceros label readings did not produce a second solution. Separate shutter exposures, objective optics and a second pointing remain alternatives for the unassigned images.
Forty-eight exposure groups recover a coherent stellar geometry. Dominant shifts are (29.55, −0.40) and (22.05, 0.40) binned pixels, about twice those offsets in native scan pixels.
A convincing pattern match and a validated distortion model are different measurements. This plate has enough information for the former, but not yet the latter.
The revised layer uses local contrast in both polarities, expanded inspected writing regions and contextual recovery of short fragments and round digits. Known photographic targets and sampled spectral apertures are protected. It is not OCR and does not reconstruct hidden sky or invent pen strokes.
The selection covers 1.73% of this scan (509,930 pixels). Faint marks, scratches and contacts between ink and photographic images remain ambiguous. The cyan overlay shows the wider exclusion footprint used by the photographic remainder; the stroke mask is supplied separately.
The writing PNG is a white, contrast-rendered stencil of bright and dark observed marks. The observed-pixel PNG preserves their stretched scan appearance. Both use original scan coordinates. The photographic remainder displays excluded pixels as black holes. It is neither a clean-sky reconstruction nor a new photometric product. Keep the mask alongside any measurements. Native original-intensity TIFF/FITS products, where generated, remain in the analysis workspace and are not duplicated in this handoff.
This revision recovers short letter fragments, round digits and inspected dark marks, with broader writing regions. The stroke selection grows from 145,562 to 509,930 pixels (3.50×). The photographic remainder uses a separate 3-pixel exclusion margin, covering 3.11% of the scan.
The wider selection deliberately favors removing writing. Nearby stars, scratches and ambiguous fragments can also be excluded. Explicit photographic protection regions retain known target images and sampled spectra; this does not establish perfect separation elsewhere.
The blind grouped solve uses index 4207-01. It places the field at 07h 34m 38.62s, +31° 53′ 25.14″, spanning about 0.760 × 0.611 degrees, at 0.452 arcsec per native pixel.
The DSS2 image is resampled into the recovered plate orientation and footprint. Its photographic epochs, bands, resolution and contrast differ. Brightness and morphology need not match. It is context from the recovered WCS, not an additional independent fit check.
The primary sky solution centers on α Geminorum (Castor). A roughly 59-pixel repeated-image family has reference support in that field; a roughly 44-pixel family has not been assigned to it. Bounded searches around tentative Monoceros label readings did not produce a second solution. Separate shutter exposures, objective optics and a second pointing remain alternatives for the unassigned images.
The central catalog star is Castor. Its modern position is not the correct location for a 1918 image: a linear proper-motion estimate moves the group-center prediction by approximately 43 native pixels. An expected exposure member then lies close to a small photographic image beside the handwritten “98”. This is a plausible target identification, not a fitted binary orbit.
Bright targets in long-focus parallax photography were often deliberately attenuated to resemble the reference stars. A contemporary 1918 account discusses that practice at Yerkes, making attenuation a plausible explanation for Castor’s modest plate image. The exact hardware on this plate is unverified. The DSS halo also depends on its own exposure, band and stretch; its apparent size is not the stellar photosphere.
The epoch check uses a nominal 26 November 1918 date and SIMBAD system proper motion. Binary orbital motion, component photocenters, exact date and exposure offsets remain approximations. Candidate pixels must be reviewed in the original scan because nearby writing makes the mask ambiguous.
Across these scans, repeated photographic images need not imply the same mechanism. Shutter timing, guiding offsets, objective optics and different pointings can leave related patterns. Establish consistent component membership before fitting a smooth warp. No result here isolates glass deformation from telescope optics, emulsion, scanner geometry and centroid bias.
Sixteen reference associations were available. Reserving five leaves only eleven training stars, below the fitting threshold. The initial field identification is retained; no held-out model comparison or independently validated distortion precision is reported. A stale “unclassified” value in the exported solution JSON is an earlier pipeline label, not this report’s visual assessment.
The included WCS records the grouped-source field solution. It is not a measured glass correction and does not map every member of a repeated exposure independently. No rectified image has been generated.
The reference footprint describes where the model is constrained. A smooth polynomial outside that footprint can look plausible while remaining unmeasured.
Reference catalogs were not propagated to the plate epoch. Proper motion, centering errors, repeated images, optical projection, emulsion, the glass and the scanner may all contribute to residuals. One scan cannot separate these physical causes.
Batch held-out stars were excluded from distortion fitting, but may have participated in the initial field identification. They are not a wholly independent astrometric experiment.
Select a numbered pin or a note. Locations are editorial review pointers, not measured confidence contours; plate-wide limitations also apply.
Incomplete groups and blended images may shift the representative coordinate.
The plotted solver correspondences are identification evidence only. There are no independent residuals to turn into a spatial correction claim.
The annotation layer may omit faint strokes or retain a photographic fragment where the two touch.
Add reliable reference centroids and jointly fit exposure translations. Preserve an adequate independent test set before trying a polynomial warp.
Share this as an identified field with an unvalidated distortion model, not as a precision-corrected scan.
All scientific numbers are snapshots of the saved analysis products. The original 16-bit scans remain the measurement source. JPEG derivatives, contrast stretching and masked previews are inspection tools; do not derive photographic density or absolute response from their appearance.
