alfredo caronia Aug 31, 2012
> Thank for your info and advice![Non-text portions of this message have been removed]
> Il giorno 31/ago/2012 15:53, "Bill J Gray" <pluto@...> ha
>> alfredo caronia wrote:
>> > As user of Guide 8 , i will know how it is possible to calculate
>> > date of opposition for any asteroid for any year!
>> At present, at least, Guide doesn't do this directly. The best
>> one can do is to click on an asteroid and make an ephemeris, then
>> search that ephemeris for an opposition date.
>> You then run into the odd problem of what an "opposition" is. Does
>> it mean the object is 180 degrees from the sun in ecliptic longitude?
>> Or in right ascension? Or does it mean the object's elongation is at
>> a maximum? Or maybe maximum magnitude? All of these definitions
>> have their proponents.
>> The differences are of minor importance for planets, because their
>> orbits are pretty much in the same plane as the earth's. They loom
>> larger for asteroids, which can have very unusual apparent motions
>> as seen from earth.
>> -- Bill