Stars and telescopes; a hand-book of popular astronomy, founded on the 9th ed. of Lynn's Celestial motions (1899)
Todd, David P. (David Peck), 1855-1939, Lynn, William Thynne, 1835-1911. Celestial motions · Boston, Little, Brown and company · leaf 401
re the positive orRamsden eyepiece (used for micrometers and allkinds of astronomical instruments requiring a reticle),and the negative or Huygenian eyepiece (usually em-ployed for gazing work merely). It is essential thatthe eyepiece should be achromatic as well as the ob-jective. The Steinheil… … ocular is especially good on stars and planets. Directobservation of the sun requires a polarizing eyepiece,or helioscope, best made in this country by Brashear.It reduces the intense solar light and heat to a degreenot harmful to the delicate tissues of the eye. The micrometer is an accessory of…
Astronomy
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