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