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Re: Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
From: Frank Reed CT
Date: 2005 Feb 12, 07:38 EST
From: Frank Reed CT
Date: 2005 Feb 12, 07:38 EST
Alex, you wrote:
"after long practice I can achieve 0.2 to 0.3 accuracy most of the
time,
with my 7x scope, both for lunar and star-to star distances."
with my 7x scope, both for lunar and star-to star distances."
Interesting. I remember you were puzzled by the star-star distances a
couple of months ago. Are you saying that they have finally fallen in line to
your satisfaction?
And:
"my common mistake in the beginning was to observe
very bright Moon. It obscures the star. One has to use
a filter, sometimes two, on the Moon, so that the star is
well visible when it touches.
Same applies to a pair of stars where one is substantially brighter.
In general, better results with star-to-star distances can be
achieved with stars that are not very bright. Same applies to index
check with stars: use a weak star."
very bright Moon. It obscures the star. One has to use
a filter, sometimes two, on the Moon, so that the star is
well visible when it touches.
Same applies to a pair of stars where one is substantially brighter.
In general, better results with star-to-star distances can be
achieved with stars that are not very bright. Same applies to index
check with stars: use a weak star."
Aha. That makes good sense. Myself, I'm always fiddling with the filters
until the images are as "dot-like" as possible. A bright star inevitably has a
dazzling halo of little rays around (these are formed in the eye if I understand
correctly (?)) which makes it difficult to decide just where it is in the visual
field.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
