Questions about Xephem and mars orbits...

I use Xephem now to look at where mars is relative to earth.
I do read about elliptic orbits, in the display of that program
the orbits are round.
Is there a way to find out how far for example mars is from the
sun at any time?
This because of the changes in climate perhaps due to the change in distance
to the sun.
Wanted to run it backwards to see where it was in the ellipse when Lovell
noticed those channels...
Maybe they will fill again ;-)
The display is a bit small to allow elliptic orbits to be drawn perhaps, but
one could have a few distance numbers perhaps next to the planets.
JP

In article , Jan Panteltje wrote:
I use Xephem now to look at where mars is relative to earth.
I do read about elliptic orbits, in the display of that program
the orbits are round.

You're looking at the Solar System view with trails over
some period of time? If you just look at the Solar System view
by default, you'll see a bunch of concentric circles that are
just there as grid lines, pretty much -- those green things aren't
orbits.

Ellipses that aren't too wildly eccentric look awfully close
to circles, with the center a bit displaced.

Is there a way to find out how far for example mars is from the
sun at any time?

Yes -- from the main panel,
View - Data Table, and then from the Data Table panel pick Control.
On the control panel select SnDst (and maybe EaDst to see distance
from Earth too) and click OK.

You can also use the main-panel Tools - Plot values feature.
I just used that today to make plots of Mars altitude vs. time-of-night
for various dates. It's quite a nice design.

On a sunny day (Sun, 13 Jul 2003 07:11:45 GMT) it happened
(Stuart Levy) wrote in
:

Is there a way to find out how far for example mars is from the
sun at any time?

Yes -- from the main panel,
View - Data Table, and then from the Data Table panel pick Control.
On the control panel select SnDst (and maybe EaDst to see distance
from Earth too) and click OK.
Hey, that is a cool feature!
Thank you for pointing it out!
JP