Discovery Board

Book or paper

Bonilla, J. A. y, Passage sur le disque solaire d'un essaim de corpuscules, vu a l'Observatoire de Zacatecas (Mexique), L'Astronomie 4 (September 1885) 347-350, with editor's note; Google scan on the Internet Archive (lastronomie03flamgoog)

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How it connects

This book or paper is where we read about Optics: a 16 cm telescope cannot hold anything farther than about 23-30 km in sharper focus than the Sun; for the Sun to look blurred on Bonilla's photo, the body was within about 0.6-4 km

This book or paper is where we read about Bonilla's report: on his photograph 'the image of the Sun is not in focus, but that of the body is'; focused on the bodies, that night the planets were out of focus and 'only the Moon was almost in focus'