Hello John, there are several method to calculate the instant of the upper culmination of Mars on June 21 : I describe shortly 3 of them
1st method >From Sky and Telescope (June 2001) we have that Mars, at June 21, has a RA = 17h 17m (interpolated value) and a Declination =-26 40' (interpolated value) Mars passes therefore on the meridian about 43m before the Midnight (Local Time) for all the places of the Earth. Being your Long. = 111d West, your midnight happens at 111/15 = 7h 24m UT (Greenwich Time) and therefore Mars is on your meridian at 6h 41m UT (about) It's height is = 90 - Lat + Decl = 30d 50 ' (about ) 2 ' method using: http:/aa.usno.navy.mil / -> Data service -> Celestial Navigation Data you can find that the GHA (Greenwich Hour Angle) = 111d (your Longitude) at 6h 42m 30s The height of Mars in your place = 30d 46.2 ' (Refraction correction 1.7 ') The occurrence that GHA = your Longitude means that Mars is exactly on your meridian 3 ' method using: http:/aa.usno.navy.mil / -> Data service -> Web version of MCA -> Rise, set and Transit you can find that Mars transits at the 23h 37m of June 21 with the height = 31d (with TZ=7) or at 22h 37m if your TZ=8 As you see it is not necessary to set the alarm clock and to get up soon :-) My wishes for a clear night ! Gianni Ferrari
