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Marcel,

Whatever are the standard conditions for the Nautical Almanac, which I
don't have here at work.  As I recall it's about 29.9 inches of mercury
for air pressure and about 50 F for air temperature.

You could go into the USNO site to its navigation calculator and get it
to show the altitude and azimuth of various objects.  It also shows
refraction for objects.  Then adjust the conditions to get the desired
altitude (including the refraction correction) & read off the
refraction.

I don't know whether the web site discusses temp and pressure.  The
Almanac has a table of corrections for temp and pressure away from
standard conditions near the front cover.

Fred

On Aug 29, 2005, at 12:05 PM, Marcel E. Tschudin wrote:

> Fred did send recently these refraction values for Frank:
>
>> Frank,
>>
>> You could ooze them out of the USNO site.  But here goes, all
>> corrections negative arcminuutes. Altitude in degrees with minutes
>> behind decimal point.
>>
>> d.'     corr
>> 0.0     33.8
>> 15      30.9
>> 30      28.3
>> 45      26.1
>> 1.0     24.1
>> 1.15    22.3
>> 1.30    20.8
>> 1.45    19.4
>> 2.0     18.2
>> 2.15    17.1
>> 2.30    16.1
>> 2.45    15.2
>> 3.0     14.3
>
> I tried to find them on the USNO site and with the help of
> Google...unfortunately without luck. May I therefore ask someone in the
> list - may be you Fred? - to what atmospheric (standard) conditions
> (temperature and air pressure) they refer to?
>
> Thank you.
> Marcel
>

   

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