An old brown square paper with a disc carrying several circular scales. Two smaller discs with indexes can be rotated. The indexes are labeled 'Sun's Index' and 'Moon's Index'. Credits for all images: Daniel Crouch rare books.
Back of the previous item, title 'The Luminarium', with 3 arcs carrying numbers (days of the month; week days, age of the Moon. Below a text provides a guide for these scales and the back.
🔭 🧪 #astrohistory
James Ferguson's 'Luminarium', a very rare card #volvelle (~1760).
For any date, the volvelle provides the duration of the semi-diurnal arc, or half-length of the day, from which you can find the sunrise/sunset times (for London) by adding or substracting from noon.
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