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Old 30-10-2011, 08:48 AM
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glenc (Glen)
star-hopper

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Join Date: Jun 2005
Location: Terranora
Posts: 4,372
Dunlop's telescope.

Dunlop's 1826 telescope was 9" (23 cm) in aperture and 9' (2.7 m) in focal length.
His two speculum mirrors reflected about 65% of the light each or 42% if you count the reflections at the primary and the secondary. Today's aluminium mirrors reflect about 93% of the light or 86% if you count the reflections at the primary and the secondary. This means his 9" was about equal to a 6.3" Newtonian with two aluminium mirrors. He had to climb a ladder to discover objects high in the sky, and use a candle to write notes and to read the clock and the south polar distance (declination) 185 years ago at his house in Hunter St. Parramatta NSW. The attached Google Earth image shows the location of his house and the backyard observatory where he made catalogues of clusters, nebulae and double stars.
The church 50m east of Dunlop's house is St Johns. http://english.stjohnscathedral.org....-/our-heritage
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Last edited by glenc; 30-10-2011 at 09:06 AM.
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