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I also have ICE Version 0.51(Interactive Computer Ephemeris) by the US Naval 
Observatory Nautical Almanac Office  available for anyone who wants it.

It gives data I believe to full precision astronomical almanac level.

It is quite basic in use being an old Dos based programme and uses the 
function keys a lot, but is OK when you are used to it. It is not simple 
point and click as in windows.

The default values can be changed for your exact location, and the 'nav' 
facility then gives a direct output of Hc and Az for all the normal 
astronomical bodies for your location for any time entered.
This is useful to check sextant observations for calibration using celestial 
bodies for your reference object as it can be done in seconds.

The only minor problem is delta T is fixed and is currently about five seconds 
'out' but that can be easily allowed for when entering time.  (I have looked 
at the files and cannot find how delta T is stored so it then could be 
changed. It might be calculated by some algorithm, though I expect more 
likely it is in a look-up table).

I thought I would upload it in Zip format for anyone who wanted to use it here 
but it will not upload, probably due to potential virus constraints.
I think it is readily available if you look around on the internet.
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Using any four year cycle of nautical almanac books is probably adequate for 
practical navigation within a few minutes of arc for the sun and stars.
Here again we can get into arguments and the semantics of just exactly what is 
'accurate' navigation in a theoretical sense as opposed to what accuracy is 
required for _practical_ navigation.  

As an example of what I mean:
I have a copy of Encyclopaedia Britannica for 1797 which has a table of 
declinations of the Sun over a four year cycle for practical navigation use 
for latitude by noon meridian sight of the sun.  It is only 'out' by around 
12 min of arc when compared with a modern almanac, and could, if you were 
stuck without anything else,  use it still today to make landfall crossing 
the Atlantic say, (with a careful lookout) by the methods used then.

Douglas Denny.
Chichester. England.

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