Callisto Dark in front of Jupiter?

Was out looking at the coment in my scope tonight, and took a peek at
Jupiter. I noticed a dark spot at about 7 o'clock on the surface. I
thought, oh, that must be the great red spot, but, no, when I check my
software it's Callisto, in exactlty the right position. Could Callisto
(at Mag 6) appear dark against Jupiter's surface (Mag -2), much like
sunspots appear dark against the surface of the sun?

TIA,

Sean

"Sean O'Dwyer" wrote in message
...
Was out looking at the coment in my scope tonight, and took a peek at
Jupiter. I noticed a dark spot at about 7 o'clock on the surface. I
thought, oh, that must be the great red spot, but, no, when I check my
software it's Callisto, in exactlty the right position. Could Callisto
(at Mag 6) appear dark against Jupiter's surface (Mag -2), much like
sunspots appear dark against the surface of the sun?

Yes... Callisto (also Ganymede) can appear so dark it looks like a moon
shadow on the surface.

In article . net,
"Paul Lawler" wrote:

Yes... Callisto (also Ganymede) can appear so dark it looks like a moon
shadow on the surface.

That's what I thought I was looking at until I checked on the computer.
Neato. Thanks.

Sean