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Author
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Topic: Home Study 5.7 Exercises
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ferling
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posted December 27, 2005 07:10 PM
Help! I seem to be missing something. I'e run the sun sight practice in section 5.7 on page 5-18, but can't seem to come close to the published answers.
For problem 1, I came up with LHA=0, Dec Deg = N19, a-Lat = N56, but Hc 53 47.0 vice the 53 34.4 published. Block 5 data were Hc = 53 00, d = +60, Z = 180, d corr = 47, Dec min = 47.3
For problem 2, I came up with LHA = 0, Dec Deg = S12, a-Lat = S10, and Hc = 87 09.0 vice the 87 05.5 published. Block 5 data were Hc = 88 00, d = -60, Z = 180, d corr = -51, Dec min = 51.
For problem 3, I came up with LHA = 360, Dec Deg = S11, a-Lat = N36, and Hc 42 00.0 vice the published 42 00.2. Block 5 data were Hc = 43 00, d = -60, Z = 180, d corr = -60, Dec min = 59.7
(close but no cigar on pure calcualtions...)
I must be screwing something up in block 3 to get to the Dec min, but hanged if I know what. Any thoughts? I don't want to press on frustrating myself and building on bad calcualtions.
Charlie
From: Tulsa
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David Burch
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posted December 29, 2005 12:17 AM
We are still away from the office, but i did a search on "5.7" and came up with this discussion that might be useful.
http://www.starpath.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=16;t=000046#000000
will check your question 1 part in more detail tomorrow to see if this answers it. if so, it is a reminder that we sometimes have to be creative in searching the discussion to find related comments.
more soon.
From: Starpath, Seattle, WA
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ferling
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posted December 29, 2005 05:14 PM
Thanks. The discussion did confirm that I appear to have been headed in the right direction, at least on question 1. It still leaves me with the bigger problem of not being able to get the answers right.
From: Tulsa
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David Burch
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posted December 30, 2005 12:05 AM
For (1), Hs LL = 54 05.0, ic=-2.0 (on take it off) and dip = -2.9 so Ha = 54 05 -2.0-2.9= 54 0.1, alt cor = +15.3, so Ho = 54 0.1+15.3 = 54 15.4.
alon = 164 23.3 so LHA = 0, aLat = 56 00, and dec = 19 34.4 same name. from 249 tables, Hc = 53 00, d=+60' Z= 180, LHA >180, hence Zn = 360-Z = 180. d corr = +34.4' (see referenced note) so Hc = 53 34.4
a = Ho - Hc = 54 15.4 = 53 75.4 - 53 34.4 = 41' and since Ho is larger it is Toward, a=31.0'T180, that will be to the south of the aLat of 56 N, which we write as 55 60 then - 41' = 55 19.0 N.
sorry for the rush. hope that helps. If this is too abbreviated, i will write up the steps more clearly. we got tied up today and i just noticed this late Thursday. (we are about to launch the full archive of all Navigator's Newsletters from the Navigation Foundation, and in the excitement of just finishing, we forgot to do our work!)
From: Starpath, Seattle, WA
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ferling
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posted December 30, 2005 09:35 PM
Lesson learned. If you pay careful attention and copy the correct data from the tables, you get the right answer.
Thanks for all of your help. Once I went back and did each of the problems carefully again, I came up with the published answers. Your reply was self explanatory and got me to look at the tables again.
From: Tulsa
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