Page 409 - 89 history of astronomy_opt

Rosse’s 6-foot reflector, 54 feet focal length,
constructed in 1845, is still the largest ever
made. The imperfections of our atmosphere
are against the use of such large apertures,
unless it be on high mountains. During
the last half century excellent specula have
been made of silvered glass, and Dr. Com-
mon’s 5-foot speculum (removed, since his
death, to Harvard) has done excellent work.
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