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Re: telegraphic longitude article
From: Fred Hebard
Date: 2003 Dec 26, 21:05 -0500
From: Fred Hebard
Date: 2003 Dec 26, 21:05 -0500
I regret not having read Chauvenet's manual, which I expect covers all this (and hope I can understand the book when I receive it!). But, how would this technique allow the transit times to be cancelled. I apologize for my lack of comprehension. Fred Hebard On Dec 26, 2003, at 7:04 PM, George Huxtable wrote: > I doubt if there were relays involved in the telegraphs for that > purpose at > that time. Observer A would tap a key when a star crossed (one of > many) > hairs in his transit telescope, and then a current pulse would flow > down > the wire. At both ends A and B of the wire would be a chronograph, > which > was a recording galvanometer, which drew a trace of the resulting > current-pulses. A single master-clock, somewhere in the system, added > timing pulses to the trace, at the two ends. Times were recorded at > both > ends when a star passed over observer A, and again when the same star > passed over observer B. > > This technique allowed the transit time of the elactrical signals to be > cancelled out.