Hallo Alain, in astronomy the two words "meridian passage" and "culmination" are (almost) synonymous and therefore I think that, in the software of which you speak, they are used for the same phenomenon.
In page 724 of the Explanatory Supplement to the Astronomical Almanac we may read: " CULMINATION : culmination passage of a celestial object across the observer's meridian; also called "meridian passage." More precisely, culmination is the passage through the point of greatest altitude in the diurnal path. Upper culmination (also called "culmination above pole" for circumpolar stars and the Moon) or transit is the crossing closer to the observer's zenith. Lower culmination (also called "culmination below pole" for circumpolar stars and the Moon) is the crossing farther from the zenith." The height above the horizon at upper culmination of a celestial body with Declination = d is H_uc = 90 - Lat + d (measured from South) or = 90 + Lat - d if measured from North For example with Lat = 50d , if the declination of the Sun is d = 20d , we have H_uc=60 d (measured from South) For a star with declination = 80d we have H_uc=60d measured by North The height above the horizon at lower culmination of a celestial body with Declination = d is H_lc = Lat + d - 90 (measured from North) For example with Lat = 50d, if the declination of the Sun is d = 20d , we have H_lc= -20d (the Sun is under the horizon) For a star with declination d = 80d, we have H_lc=+40d For a place with Lat = 75d and with the Sun with d = 20d , we have at upper culmination H= +35 measured from South and at lower c., H = + 5 measured from North (the Sun doesn't set) Regards - Gianni Ferrari ----- Original Message ----- From: Alain MORY <[EMAIL PROTECTED]> To: <[email protected]> Sent: Saturday, June 16, 2001 10:25 PM Subject: meridian or culmination ? > > Hello, > > I was surprised to sea a software dedicated for astronomy showing other > times for "passage au mČridien" and for "culmination" of the sun. > > Why is there such a difference between these two notions ? > > Alain MORY > 48N 7E > >
