Tiziano, you are absolutely right; Venus, Uranus, and Pluto
misbehave in different ways. I have tracked down this bug. (It also
affects Pluto's moon Charon, which rotates in the same manner as
Pluto. The moons of Uranus would also be affected, if they had
bitmaps.)
Fixing it may be a little difficult, though; any changes would
cause the existing bitmaps to be flipped. For the "cloud" images
of Uranus and Venus, this doesn't really matter. But the images
for Pluto, Charon, and the radar-based Magellan image for Venus
are correct right now. I'll have to figure out a way of fixing
this which preserves the "legacy" images for these objects. It's
not the first time the bizarre IAU "north-centric" system has
tripped me up... thought I'd caught all these oddities, though.
In order to get all of these images to work in the first place,
I had to do assorted flipping and rotating for almost all of the
planets, not just the retrograde one. Some images were provided
starting at longitude 0, others at 180, one (the radar image of
Venus) at 120. I generally rotate Jupiter images a bit to ensure
that the Great Red Spot is placed correctly. Some images have
north up, others south. (For example, the Schiaparelli map of
Mars mentioned at
http://groups.yahoo.com/group/guide-user/message/3067
is south-up, which is why you have to set Guide to "chart
inverted" to get the text to show correctly.)
-- Bill