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Author
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Topic: home study course section 11.18
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Kevin Briggs
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posted July 03, 2005 04:22 PM
I have some differences between the textbook and my calculations. They may be my arithmetic errors or my table lookup errors.
I'm new to this and did not notice a topic. If I created this in error then I apologize.
#5
I have WT LAN 9h45m02s
I used 1978 Oct 26 Equation of time 15m58s
The textbook appears to use 5m42s; 1981 Mar 26
#6#7#8
I used the Coversion Arc to Time value 8h53m20s from 133d20m
#6 WT morning twilight Nautical 2h37m20s
textbook 2h20m20s
#7 WT morning twilight Civil 3h32m20s
textbook 3h20m20s
#8 WT sunrise 4h22m20s
textbook 4h04m20s
#9#10
I have
morning twilight Nautical 5h5m44s
textbook 5h05m20s
evening twilight Nautical 19h9m44s
textbook 19h09m20s
The textbook appears to use 75degree20min Conversion Arc to Time
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David Burch
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posted July 04, 2005 05:05 PM
Prob 5 is addressed in the Tech Support. Generally good idea to check there as well as here when suspecting typos or errors.
In Prob 6 you get LMT from NA = 02h27m for 52N on july 25, 78. from arc to time, 133° = 8h 52m, and 20' = 1m20s. Add these up to get 10h70m20s = 11h20m20s gmt = 02h02m20s WT at ZD = +9.
Pls see if that helps sort out the other ones as well.
My guess is a procedural error somewhere. In a nutshell, one looks up LMT from NA (though we do not use the term local mean time in the course at all, this is the name of the time listed in the nautical almanc for the event), then in west lon you add your lon (converted to time) and in east you subtract it, which gives you the GMT of the event, then you undo this to WT using the ZD of the watch.
Note you can read our discussion of the term Local Mean time in the text or online course glossary, and if you want to see why we do it that way -- besides its being the superior approach in all cases -- all you have to do is read the "official" definition in bowditch.
From: Starpath, Seattle, WA
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Kevin Briggs
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posted July 05, 2005 08:08 AM
Thanks for the feedback!
I do not have the textbook with me at present but I do have the CD.
#6-8
My notes have the DR as 50deg N rather than 52deg N of the CD and your reply. Probably a transcription error on my part but I thought I had verified the "given information". This is the difference.
#9-10
My notes have the DR as 75deg 26min W rather than 75deg 20min W of the CD. This is difference I identified earlier. I thought I had double-checked the "given information". My #10 is an addition error I consistently did; I identified the error by going back to decimals! Ahh, a novice!
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