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Almanac accuracy, WAS: Re: Hughes Tables.
From: Peter Hakel
Date: 2009 Jul 17, 10:20 -0700
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From: Peter Hakel
Date: 2009 Jul 17, 10:20 -0700
From two independent sources I find the GP of Fomalhaut at this time as:
GHA: 82 degrees 04.8'
Dec: S 29 degrees 34.4'
I am still learning what degree of accuracy one might realistically expect from different sources of astronomical data. I remember reading that almanacs are only guaranteed to about 0.3', so the declination values are not too far off from each other. The GHAs differ by more than I would expect. Any comments? I assume that this difference in GHA is inherited from the star's SHA, since GHA Aries is relatively straightforward to calculate. So, for completeness:
GHA Aries: 66 degrees 37.1' (the other source gives 37.0')
SHA: 15 degrees 27.7'
Peter Hakel
==== Begin quoted message fragment ====
You gave Lat 40 N. Long 77W. fomalhault on 13th July 2009 at 09-00Hrs.
I found the following:-
Using ICE 0.51 for the ephemeris data for formalhaut for 13th July 2008 09-00Hrs:-
GHA is 81-49.6
Dec is S. 29-34.0 (N.B. ICE gives an Hc for the Lat40 Long 77W of 20-17.3)
GHA: 82 degrees 04.8'
Dec: S 29 degrees 34.4'
I am still learning what degree of accuracy one might realistically expect from different sources of astronomical data. I remember reading that almanacs are only guaranteed to about 0.3', so the declination values are not too far off from each other. The GHAs differ by more than I would expect. Any comments? I assume that this difference in GHA is inherited from the star's SHA, since GHA Aries is relatively straightforward to calculate. So, for completeness:
GHA Aries: 66 degrees 37.1' (the other source gives 37.0')
SHA: 15 degrees 27.7'
Peter Hakel
==== Begin quoted message fragment ====
You gave Lat 40 N. Long 77W. fomalhault on 13th July 2009 at 09-00Hrs.
I found the following:-
Using ICE 0.51 for the ephemeris data for formalhaut for 13th July 2008 09-00Hrs:-
GHA is 81-49.6
Dec is S. 29-34.0 (N.B. ICE gives an Hc for the Lat40 Long 77W of 20-17.3)
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Or post by email to: NavList@fer3.com
To , email NavList-@fer3.com
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