First ads published in Sky and
Telescope about Ha mica-spaced etalons (and others)
Home-made Lyot filter (= monochromator)
Walter. J. Semerau
Sky&Telescope. May, 1958
Baird-Atomic, Inc.
These Ha filters were possibly dielectric filters (and not etalons). BW
were about 5 A. Images taken by A.K. Presnel in 1959 are displayed in
S&T, August 1960.
Sky&Telescope. August, 1960
Carson Astronomical, Inc. Skyspear
Introduction date: May, 1972. Last ads: June, 1974.
DayStar
Introduction date: December, 1976
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