Document fnotching eps=20 default vs eps=30 stated in paper

[michaelaye]

Summary

The fnotch_image_ids function in production/fnotching.py defaults to eps=20 pixels for the fan/blotch proximity threshold. However, the paper states 30 pixels was used.

Evidence

All production call sites invoke fnotch_image_ids(obsid, savedir=...) without an explicit eps argument, meaning the default of 20 was always used:

• production/catalog.py:201 — fnotching.fnotch_image_ids(obsid, savedir=savedir)
• production/catalog.py:197 — fnotching.fnotch_obsid(obsid, savedir=savedir)
• planet4_work/manhattan_all_years_production.ipynb — same pattern

No instance of eps=30 was found in any fnotching call across the entire codebase.

Possible source of confusion: DBScanner.eps_values["blotch"]["radius"]["small"] = 30 in production/dbscan.py — this is the DBSCAN clustering radius eps for small blotches, not the fnotching proximity distance.

Action needed

• Determine whether the paper should say 20 (matching the code) or the code default should be changed to 30 (matching the paper)
• Document the correct value in the fnotching docstring
• If 20 is correct, update the paper

Found by student code review.

[michaelaye]

updating the paper is not possible anymore, we should put that into the p4tools docs at a prominent place. TBD.