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SkyMap and the calendar?

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Jakob Wittmann

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Dec 20, 1998, 3:00:00 AM12/20/98
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Hello,

Perhaps anybody knows...
If I (location lat...alt...) want (only for example) to know the position of
Venus on May2nd 10:23 UT in the year 1066, would all historical corrections
of our calendar be implemented in the calculation or not?
(Would be a great help for chronological control in certain historical
documents)

Greetings

Jakob

Chris Marriott

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Dec 20, 1998, 3:00:00 AM12/20/98
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Jakob Wittmann wrote in message <75jjtb$9go$1...@news.netway.at>...

>Hello,
>
>Perhaps anybody knows...
>If I (location lat...alt...) want (only for example) to know the position
of
>Venus on May2nd 10:23 UT in the year 1066, would all historical corrections
>of our calendar be implemented in the calculation or not?

SkyMap takes any date on or after 15th October 1582 as being in the
Gregorian calendar; any date before this as being in the Julian calendar.

Short answer - yes.

Chris
-----------------------------------------------------------------------
Chris Marriott, SkyMap Software, UK (ch...@skymap.com)
Visit our web site at http://www.skymap.com
Astronomy software written by astronomers, for astronomers


Geoff Clare

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Dec 22, 1998, 3:00:00 AM12/22/98
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"Chris Marriott" <ch...@NOSPAM.skymap.com> writes:

>>If I (location lat...alt...) want (only for example) to know the position
>of
>>Venus on May2nd 10:23 UT in the year 1066, would all historical corrections
>>of our calendar be implemented in the calculation or not?

>SkyMap takes any date on or after 15th October 1582 as being in the
>Gregorian calendar; any date before this as being in the Julian calendar.

>Short answer - yes.

But what does it do about the start-of-year changing from March 25th
to January 1st?

Does it just use January 1st for all years, like the Unix "cal" utility?
(which documents this limitation in the man page: "The year is always
considered to start in January even though this is historically naive.")

This would not affect the calculations for May 2nd 1066, but it would
for, say, Feb 2nd 1066 (which was 9 months after May 2nd 1066).
--
Geoff Clare <g...@root.co.uk>
UniSoft Limited, London, England.

Chris Marriott

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Dec 22, 1998, 3:00:00 AM12/22/98
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Geoff Clare wrote in message ...

>
>But what does it do about the start-of-year changing from March 25th
>to January 1st?
>
>Does it just use January 1st for all years, like the Unix "cal" utility?
>(which documents this limitation in the man page: "The year is always
>considered to start in January even though this is historically naive.")

Yes, it always takes Jan 1st as the start of the year. I'm not aware of any
astronomy software which doesn't - I think that everyone (including me)
takes the view that if you're involved in historical research, you know the
basics of calendar "rules".

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