Sun rise time. Temperature and level above the sea

[Guest guest]

Dear Yuri,

 

Whether USNO calculations are accurate or not, the issue of apparent Sun

position is not so simple.

Your example for Edmonton, Alberta, Canada (5:03:58 local time) is

calculated for +20°C and normal atmospheric pressure (1013 mBar). The city

is 2201 feet (671 meters) above sea level and if you set

geopos[2]:= 671; atpress:= 0; the time will be 05:04:26.

Also the temperature affects the rising time for apparent position

significantly (about 1 minute difference for

T= -20°C).

 

IMHO the true position (without refraction) should be used to avoid

ambiguity because we don't take

the birth place temperature and elevation above the sea into consideration.

 

Bogdan

www.astromagus.com

 

 

-

<khmelevsky

> With accordance to the Swiss Ephemeris, that should be "the tip of the

> Sun's disk appears to be on the eastern horizon", but not "the tip of

> Sun's disk is truly on the eastern horizon". If that is for "the tip

> of the Sun's disk appears to be on the eastern horizon", that is OK.

>

> >From the other side, I did met some complains about U.S. Naval

> Observatory Astronomical Applications Department calculation accuracy

> in several astrology forums just several days ago.