John Banister wrote:
Anyone view Jupiter last night (8/1/06)? If so did you notice a small dark
oval moving along the north equitorial band from 22:00 CDT (03:00 GMT) to
23:00 CDT? It initially looked like a shadow of a moon but my software
indicates that there was no shadow at the time, and the dark oval seemed to
be flattened, rather than round. North-south it seemed to be about the same
size as a moon shadow but was about twice as wide on the East West axis.
Here is my observing report:

"C10 NGT at 200X. N&S Eq bands evident. Swirling in Eq zone. 22:08:
observed small black blotch on southern edge of N Eq band. Initially thought
it might be a moon shadow, but no shadowing at that time. Blotch was a
flattened oval about 5 deg. E of meridian. Reobserved at 22:49L. Blotch
still evident on S. edge of N. Eq band, this time abut 20 deg from W limb.
Blotch was followed by a larger white oval which seemed to touch black
blotch and extend to the meridian, i.e. trailing edge of white oval was on
the meridian and leading edge W. of meridian, touching black spotch. White
oval looked a bit like Great Red Spot in shape but was about 3/4 it's size.
No color on planet noted, so objects mentioned could be colored instead of
black and white. 4 Jovian moons evident W/ 20 mm (60X)."
Thanks.


What you observed is very likely a festoon (there are 13 of them) as
they can be quite dark where they touch the NEBs (let's say at their
"root"). Some, but not all, are accompanied by a bright ammonia spot (a
source) so what you observed is quite plausible.

Andrea T.