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Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
From: Pierre Brial
Date: 2005 Feb 11, 22:38 +0400
From: Pierre Brial
Date: 2005 Feb 11, 22:38 +0400
Hi Frank, > Frank Reed a ?crit: > > Pierre Brial, you wrote: > "Not yet. My sextant has a mechanical accuracy of 0.2', but despite > the > fact I have adjusted it, repeated tests on star distances show me that > it is difficult to have a practical accuracy of under 0.8'. But may be > this is also because of my lack of experience or inaccuracies in my > eye." > > Do you have a good telescope on it? I have found that I can only get > down to 0.2' accuracy with a 7x35 monocular on my sextant. I think you got the point. I've got a 3.5x38 telescope. Recently I tried a lunar distance with Saturn. The ephemeris give for Saturn a semi diameter of 0.2', that is a whole diameter of 0.4'. But through the scope, I see only a spot. A bright one, but nevertheless a spot. So the magnification is too small to get a 0.4' accuracy. > "Are these [Bowditch] notes available somewhere ? Foreign accounts on Reunion for > 18th century are not well known here..." > > It's in the Boston Public Library in Massachusetts. I have only read > summary accounts, but next time I'm out east, it's on my list of > things to read. I'll let you know if there's more of interest > regarding Reunion. I will be very grateful if you can find informations about this. Also let me know in case these note will be published. Best regards Pierre Brial