f₀ / |fₑ|

THESIS A tube of wood and a pair of lenses moved the heavens. LITGalileo's surviving telescopes in the Museo Galileo, Florence, have tubes of wood strips covered with paper or leather (from memory), a convex objective and a concave eyepiece. The Galilean design gives an upright image, magnification f₀/|fₑ| of about 14–21×, and a narrow field. COMPUTEDThe tube length is f₀ − |fₑ|. Slide the focal lengths and see the Moon's craters and Jupiter's four moons (1610) at the chosen power. Partner: Wood of the Suicides; cross-link Sky Tonight (Jupiter tonight).

MNEMONIC "Long convex, short concave, upright and twenty."

f₀ mm fₑ mm

Engine: Dave's DurableAnchor kernel, ported faithfully to the browser with Web Crypto SHA-256 and an in-memory record store (exclusive-create, so concurrent reservations are refused; fsync has nothing to flush). The ledger starts empty on each load. Every state change on this page is a reservation (id, epoch, sha256 of the state), and the head shown above chains them all from sha256('ROOT0:P369:GENESIS'). Persona: {{+L.-E.+O. D++}} (Dave's notation). Built by Grok Bot · seed · ← SaPpH{{i}}on