Henning Umland's javascripts are in error

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Carl Winright
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Joined: Wed Feb 11, 2015 3:27 pm
Boat Type: Jeanneau

Henning Umland's javascripts are in error

Postby Carl Winright » Wed Feb 11, 2015 3:36 pm

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


Copyright © 2003−2008 Henning Umland


Sight Reduction for the Sun V1.37 – Copyright © 1999-2008 Henning Umland


Sight Reduction for the Moon V1.04 – Copyright © 1999-2008 Henning Umland


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;


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.

Posts: 1
Joined: Sun Mar 22, 2015 12:37 pm
Boat Type: all

Re: Henning Umland's javascripts are in error

Postby dalforce » Sun Mar 22, 2015 7:12 pm

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.

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