Transit of Phobos

[eburacum45]

I have been told that a transit of Phobos will be visible from the Opportunity rover on 6 March at 19.22 UTC;

So I tried to see this event using Celestia;
first I set the time to 19.22 and paused it, then went to the Sun, then to Phobos- then back to the Sun, then back to Phobos; this longwinded procedure ensured that I was aligned with the Sun and Phobos; then I accelerated through Phobos until I was a few metres above Mars (a quick cntl+G ensured I was standing on the Surface;)

then I captured this image of the transit at 19.22 6/3/4 UTC



However I was apparently nowhere near Opportunity at that point, and setting the location to Meridani Sinus does not produce a transit;
so I was observing this transit from an unknown point-
how can I find out the latitude and logitude of this observation?

[ElPelado]

Just one simple question: that blue color is not mars atmosphere right???

[Guest]

Well, no;

We have a partially terraformed Mars in the Orion's Arm scenario; I used that atmosphere in this shot- well spotted!

[selden]

To see numeric values for the current latitude and longitude relative to the currently selected object on a Windows system, open the Navigation/"GoTo Object" menu.

It doesn't update dynamically, so you'll have to close and open it again if you change your location using the mouse or keyboard.

You also may have to convert Celestia's signed East longitude value to a more appropriate longitude standard.

[Guest]

Thank you!

By the way, I have discovered my informant's mistake;

he forgot to allow for the fact that Mars is not actually transparent...

[Harry]

(2nd try for this post)

To see numeric values for the current latitude and longitude relative to the currently selected object on a Windows system, open the Navigation/"GoTo Object" menu.

It doesn't update dynamically, so you'll have to close and open it again if you change your location using the mouse or keyboard.

I've just written a script which displays the current longitude and latitude, get it here:
http://www.h-schmidt.net/celestia/showlonglat.celx
I hope I got the coordinate conversion right this time but it may still be buggy.

Harald

[JackHiggins]

Nice pic eburacum- saw a similar one posted by yourself on badastro a few days ago...

On a related topic- i've seen lots of pics posted online (From Viking, MGS, Odyssey etc) of penumbra shadows on mars' surface because of the transits by phobos. However, if I make phobos into a sphere (3ds objects can't cast shadows) there is no shadow visible on the surface.

I'm guessing there's some sort of size:distance ratio for rendering eclipses which is being set too low- any chance this could be changed?

[ElPelado]

I was thinking of adding a small planet inside phobos with the same orbit so it will cast at least a circular shadow...

[JackHiggins]

Well, yeah, thats like what I tried, but celestia thinks phobos is too small to cast a shadow...

[Piper]

It's actually Deimos that's transiting, not Phobos. Although, when I went to the Opportunity site, it wouldn't transit till March 10th. As for Phobos, it transits the Spirit landing site sometime in April.

[chris]

The orbits of Phobos and Deimos are purely Keplerian right now--I don't think they're accurate enough for reproducing eclipses. Phobos's orbit precesses at about 0.435 degrees per day, and Deimos orbit precesses 0.018 degrees per day. I think that's enough to explain the missing eclipses. Time to create custom orbits for these bodies . . .

--Chris

[JackHiggins]

Some images of deimos transit here:

http://marsrovers.jpl.nasa.gov/gallery/ ... _p039.html

Only very tiny images at present however...