Bluemoment and a lot of other websites link to Henning Umland's celestial navigation website and javascripts. They are in error and very inaccurate.
Here's Umland's "freeware" link; http://www.celnav.de/page3.htm
The following are the Umland programs I've compared with the USNO;
Long Term Almanac for Sun, Moon, Brighter Planets and Polaris 1.14 by H. Umland
...and...
LONG-TERM ALMANAC FOR MOON, STARS, AND LUNAR DISTANCES V1.13
Copyright © 2003−2008 Henning Umland
...and...
Sight Reduction for the Sun V1.37 – Copyright © 1999-2008 Henning Umland
...and...
Sight Reduction for the Moon V1.04 – Copyright © 1999-2008 Henning Umland
...and...
Sight Reduction Calculator V1.50 – Copyright © 1998-2008 Henning Umland
If you enter the same data for the sight, such as...
Date- Feb 3, 2015
UTC= 17
Ap Latitude- N 55
Ap Longitude- W 010
...the answers are wrong by a large margin.
Compare the results with those obtained at the USNO;
http://aa.usno.navy....celnavtable.php
Apparently he hasn't updated his javascripts as the code for them is out of date. He's also unreachable except by "fax".
So, if you're interested in Celestial Navigation and using his scripts but can't figure out why you're getting wrong answers it's probably not your fault.
Henning Umland's javascripts are in error
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Carl Winright
- Midshipman
- Posts: 1
- Joined: Wed Feb 11, 2015 3:27 pm
- Boat Type: Jeanneau
Re: Henning Umland's javascripts are in error
I have noticed the same anomaly (about 1 degree error of Hc and Zn) on the 'sunsight. htm' calculator that requires only date/time of sight and position as inputs.
'sightred' .htm, which requires an input of GHA and Dec. seems to calculate Hc and Zn in line with the date from this online site
http://aa.usno.navy.mil/data/docs/celnavtable.php#notes , so remains a useful tool. As they are distributed freely, I'm surprised that someone with the necessary skills has not corrected them.
It is a pity that Henning Umland is so difficult to contact*, as the format and ease of use of his calculators, ie not needing an internet connection, make them most attractive tools.
* Finding anyone who has a fax machine is not so easy these days.
'sightred' .htm, which requires an input of GHA and Dec. seems to calculate Hc and Zn in line with the date from this online site
http://aa.usno.navy.mil/data/docs/celnavtable.php#notes , so remains a useful tool. As they are distributed freely, I'm surprised that someone with the necessary skills has not corrected them.
It is a pity that Henning Umland is so difficult to contact*, as the format and ease of use of his calculators, ie not needing an internet connection, make them most attractive tools.
* Finding anyone who has a fax machine is not so easy these days.