Eric wrote:

I see articles where they have taken 2 pics of an object,(eg a comet or
asteroid) and the movement from pic 1 to pic 2 is only a part of an inch as
measured on the photos. How do they calculate the orbit of an object with
so little information?

I often wondered the same thing myself. Apparently initial orbital
calculations for comets assume they're parabolic at least removing
one degree of freedom from the calculations. Presumably initial
calculations for asteroids are that they are in circular orbits.

I understand that initial calculations aren't very accurate, but then
the next thing you here is that they've found the object in photos
from 100yrs back. Presumably you need total precision to get back
like that.

Hubble has just recovered a satellite of Uranus (Perfida ?) originally
seen in Voyager II photos. How they can tell whether it's taken n
orbits or (n+1) orbits in the intervening time I don't know.

Joe

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Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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