by Steven Caron
The fog swallowed us a Coe last night around 10:30. It came up like a giant wave from Mavericks. Earlier that night, some decent observing was done.
Phil had a new digital camera that was taking beautiful images of Saturn, Jupiter and Ganymede, though his C11. Mark, Ken and I hunted down obscure open clusters in Cassiopeia. Most notably, King 12, a nice compact, rich open cluster, with a nice double star at the center.
The highlight of the night was, for the first time I saw Amalthea, a moon of Jupiter, through Ken's 18" Obsession. Jamie doubts I saw it, but I am confident that I did. The "Planetary Observers Guild" list's Amalthea at mag. 14.1, well within the reach of the 18". The moon appeared very, very, faint, and very, close to Jupiter, but it was definitely there using 380X. Amalthea is also the reddest object in the solar system, no color was evident though.
Just as the moon went down, the fog covered us up completely. I led the was down the hill, braving the thick fog. The fog dispersed about 3/4 of the way down.
David Kingsley wrote:
According to TheSky, a mag 9.75 star was in perfect line with the Jupiter Satellites last night. This star would have been located between Jupiter and the innermost moon Io during the period from 8 pm and 11 pm. Is it possible that you saw this star instead of Amalthea? It would have been almost 5 magnitudes fainter than the Galilean moons, and much more difficult to observe than usual because of its proximity to Jupiter (very close to Jupiter around 8 pm, nearer to Io by 11 pm). It would be interesting to sketch out what you saw last night and compare it to both the position of this star and the predicted Amalthea orbit from JPL (earlier post).
Ok, here is my *very* quick sketch of Jupiter at about 9:15pm.....
I have a strange feeling that you may be right, and a all I saw was measley star. But, it sure seemed faint for mag 9, of course that may be just because the glare of Jupiter. How does this correspond to TheSky?
Your sketch corresponds to the position of the field star [HIP2099; TCY1277-1320-1; SAO76633], located between Jupiter and Io on the eastern or following side of Jupiter. In contrast, Amalthea would have been on the opposite side of the planet at 9:15 pm, according to the JPL ephemeris (western or preceeding side of Jupiter, position angle 257).As a mark of just how difficult a target Amalthea really is, it would be more than 4 magnitudes fainter than this mag 9.7 field star. Very tough in Jupiter's glare, and probably requiring an occulting bar, high magnification, a large aperture scope, and careful timing to catch it at maximal elongation.
Does anyone know of a successful visual observation of Amalthea in an amateur telescope? Sounds like a great challenge object for the very ambitious.
From now on, the star HIP20994 SAO76633 shall be known as: Caron's False Moon..... :-)