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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Silicon Sea, LEG 13
From: Mike Burkes
Date: 2012 Sep 28, 11:59 -0700
Hi Najar, you are using incorrect GMT. ZT needs to be converted to GMT as follows;
Sirius Zone Time  ZT:19-42-56
Zone difference    ZD; -1
Greenwich Time GMT 18-42-56
ZT is indicated at beginning of problem.
Mike Burkes
62-833-1521

From: alberto.najar@gmail.com
Date: Thu, 27 Sep 2012 21:47:26 -0300
Subject: [NavList] Re: Silicon Sea, LEG 13
To: NavList@fer3.com

Hi Greg,

Sorry, here we go: my problem was with the question 1. I think there is some thing wrong with the data. The text is:

"Sight Reduction and DR
----------------------     ------  ----------------------------

On 12/05/96 we are at DR(36d 13.9'N  10d 54.4'E), on a TC of 111.3d at
7.8 Kts bound for Masabb Dumyat(31d 30.1.N  31d 50.0'E).

It is 19-42-00 ZT. We decide on a set of 3 bodies for a FIX During
Evening Nautical Twilight.

Body           Time           Hs             Zn

Sirius          19-42-56       11d 46.2'      239.1d
Alioth         19-48-27       61d 55.8'      035.8d
Spica          19-54-40       31d 59.7'      137.5d

1)  What is our FIX position using Spica as the plotting time?
What is the Dist Off?"

If we work these sights we will find some thing very bizarre. I found:

LOP for Sirius
12/05/1996 19:42:56 GMT
Assumed Pos. Lat:36°13.9'N  Lon:10°54.4'E

Hs: 11°46.2'
Dip:-2.7' IC:-0.2'
Ha: 11°43.3'
Ho: 11°38.7'

GHA: 65°20.5'
Decl: 16°43.0'S
LHA: 76°14.9'

Hc:  0°46.9'
Intercept:651.8 NM (towards)
Az.calc:  248°

LOP for Alioth
12/05/1996 19:48:21 GMT
Assumed Pos. Lat:36°13.9'N  Lon:10°54.4'E

Hs: 61°55.8'
Dip:-2.7' IC:-0.2'
Ha: 61°52.9'
Ho: 61°52.3'

GHA: 334°28.3'
Decl: 55°59.0'N
LHA: 345°22.7'

Hc: 67°54.3'
Intercept:-361.9 NM (away)
Az.calc:   22°

LOP for Spica
12/05/1996 19:54:40 GMT
Assumed Pos. Lat:36°13.9'N  Lon:10°54.4'E

Hs: 31°59.7'
Dip:-2.7' IC:-0.2'
Ha: 31°56.8'
Ho: 31°55.2'

GHA: 328°16.3'
Decl: 11°08.6'S
LHA: 339°10.7'

Calculated Altitude (Hc): 38°43.1'
Intercept:-407.9 NM (away)
Az.calc:  153°

Thank you very much,

Alberto.

2012/9/27 Greg Rudzinski
Ahoy Alberto,
You will need to provide a link or details of Leg 13. Then I'll do a plot.
Greg Rudzinski
[NavList] Silicon Sea, LEG 13
From: Alberto Najar
Date: 27 Sep 2012 15:08
Dear All,
My name is Alberto Najar, I'm from Rio de Janeiro, Brazil and I regularly practice astronomical navigation in my 33 foot, a Peterson sailboat. Some days ago I was trying to solve LEG 13 from Silicon Sea and I didn't find the same results for the question 1 - the fix position - at all. I was wondering if there is something wrong. After searching in list archives and not finding anything, I decided to post a message in the hope to find any help.
Alberto.
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