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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Difference between HO 249 and USNO website
From: John A
Date: 2016 May 17, 07:33 -0700
From: John A
Date: 2016 May 17, 07:33 -0700
Hi there. I am wondering why the sight reduction results from HO 249 and the USNO website (https://aa.usno.navy.mil/data/docs/celnavtable.php) differ so much.
I've attached my own calculations using HO 249, and the results from the website. The Zn value is the same, but the Hc values are significantly different. Is this normal? Or am I doing something wrong (the most likely scenario!)
I should mention that I took the sight using a homemade 'astrolabe', so in my own calculations I am including no altitude corrections. i.e., no dip and no SD correction.
Any thoughts, much appreciated.
-- John
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