[NatureNS] astrolabe

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Date: Mon, 9 Jul 2012 18:23:12 -0400 (EDT)
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A couple of thoughts as an ancient navigator. An Astrolabe  measures 
altitude of a heavenly body and that is all it does. That means that it  can be 
used measure Latitude when the sun is bearing North or South and you are  
armed with tables giving current declination. As far as local time is concerned, 
 that is apparent noon but does not take into consideration time zones. To  
determine longitude, accurate time is needed and that wasn't possible until 
 the chronometer was invented by a fellow Lincolnshire poacher. There was 
another  way of determining longitude without time involving lunar 
observations but it  was not within the expertise of most mariners. 
An appropriate issue the day after seafarers  Sunday.
 
Captain Peter Stow 
Hubbards
 
 
In a message dated 09/07/2012 6:29:56 P.M. Atlantic Daylight Time,  
dwebster@glinx.com writes:

Hi,                   July 9, 2012
I noticed on  Wikipedia in the astrolabe article (line 4) a statement 
that appears to be  incorrect; namely that an astrolabe can be used to 
determine "...local  time given local latitude".

In the above quote should  latitude not be longitude ?

Yt, Dave Webster, Kentville  



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<DIV><FONT size=3D4>A couple of thoughts as an ancient navigator. An Astrol=
abe=20
measures altitude of a heavenly body and that is all it does. That means th=
at it=20
can be used measure Latitude when the sun is bearing North or South and you=
 are=20
armed with tables giving current declination. As far as local time is conce=
rned,=20
that is apparent noon but does not take into consideration time zones. To=
=20
determine longitude, accurate time is needed&nbsp;and that wasn't possible =
until=20
the chronometer was invented by a fellow Lincolnshire poacher. There was an=
other=20
way of determining longitude without time involving lunar observations but =
it=20
was not within the expertise of most mariners. </FONT></DIV>
<DIV><FONT size=3D4>An appropriate issue the day after seafarers=20
Sunday.</FONT></DIV>
<DIV><FONT size=3D4></FONT>&nbsp;</DIV>
<DIV><FONT size=3D4>Captain Peter Stow </FONT></DIV>
<DIV><FONT size=3D4>Hubbards</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>In a message dated 09/07/2012 6:29:56 P.M. Atlantic Daylight Time,=20
dwebster@glinx.com writes:</DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px">=
<FONT=20
  style=3D"BACKGROUND-COLOR: transparent" color=3D#000000 size=3D2=20
  face=3DArial>Hi,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &=
nbsp;=20
  &nbsp; &nbsp; &nbsp;&nbsp; July 9, 2012<BR>&nbsp; &nbsp; I noticed on=20
  Wikipedia in the astrolabe article (line 4) a statement <BR>that appears =
to be=20
  incorrect; namely that an astrolabe can be used to <BR>determine "...loca=
l=20
  time given local latitude".<BR><BR>&nbsp; &nbsp; In the above quote shoul=
d=20
  latitude not be longitude ?<BR><BR>Yt, Dave Webster, Kentville=20
<BR><BR></FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>
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