[X] My Assistant

[jamescanvin]

The twilight images are only down in thumbnail form

Here is one of those thumbnails



Working on movie...

[jamescanvin]

Movie of twilight at Gusev, taken over 23 minutes at around 18:30LST on Sol 1835



Are we seeing stars and Earth/Venus or are those just hot pixels - I'm a little surprised that there is no apparent movement as they set.

[Guest_Oersted_*]

Phobos and Deimos maybe? I seem to see two dots that move from right to left.

[fredk]

I think they're all hot pixels/CR's. Nearish the celestial equator, stars would move about one pancam-field per hour, so roughly a third of a field in the 23 minutes of this movie. It would be less if we're looking near a pole. What's the azimuth of this view?

[Deimos]

These views are just right of sunset, a bit south of west. Earth and Venus set in the frame, but I can't make them out in the thumbnails (nor did I expect to). There are plenty of hot pixels in the long exposures, and the occasional cosmic ray strike. Phobos rises and Deimos sets to the right of this field and weren't in that direction at this time.

[Stu]

Latest navcams ( http://qt.exploratorium.edu/mars/spirit/navcam/2009-06-23 ) are of twilight scenes, but there's so much crud on them (made an animation but not even going to bother posting it, it looks like a firefly party!) I can't pick anything out of the mess. Maybe others can do better.

[fredk]

Some pancams show a bright star (moon?) and a fainter one, see the trails in, eg, this frame:
http://qt.exploratorium.edu/mars/spirit/pa...E5P2738L1M1.JPG

Another pancam series at dusk shows one clear star-like point setting from frame to frame, so it's not CR/hot pixels. Check out the upper quarter of the frame in this animated gif:

My guess is Venus

[Stu]

Good catch Fred, definitely something there.

[Astro0]

Moon or spacecraft? (and by that I mean "one of our spacecraft")
Animation...


Nice to see the Gusev Astronomical Society active again

[djellison]

Phobos going into eclipse, I'd say. (Although not actually IN eclipse at that point)

[fredk]

I'll go out on a limb and guess the bright object in Astro's animation is a star. I get a motion of around 140 degrees per sol for it, which is nowhere near what you'd get for either moon, and much too slow for an orbiter, but would match a star at mid-celestial latitude. I've assumed the frames are not downsampled, just subframed.

[mhoward]

Really cool stuff. FWIW the images in fredk's animation are labeled "pancam_earth_venus," and the images in Astro0's animation are in the southern sky about 38 degrees above Von Braun, and are labeled "pancam_nighttime_opacity".

[Deimos]

The star is Canopus, which is not quite circumpolar from Gusev. It looks wide in the images only because of the extreme contrast stretch. Earth is to the lower right from Venus (about 2 deg) in the twilight animation--but it is so low contrast I'm not sure if it can be seen in the jpegs. It should become clearer over time.

[fredk]

I registered the 5 Venus-Earth pancam frames on Venus and then averaged them to try to cut down the jpeg noise. Here's the result:

One pale grey dot stands out above the noise, about 1.5 degrees to the lower right of Venus (at intersection of arrows). If you look very closely at the five individual frames, you can see it in each, so it's not a bright CR hit in one frame, and it's not a hot pixel, since they move relative to Venus (you can see some towards the bottom of the frame).

Going out on another limb, I say that dot is Mother Earth.

[helvick]

Nice work there Fred, very nice.