imaging question

[ving (David)]

a question about imaging jupiter and its moons...

I fully understand that due to the rotational speed of the planets belts you can only image jupiter for a short period otherwise i assume that you will get some sort of image shift or blurriness to the image right?

now given this, what speed do the various moons travel in relation to the cloud belts on jupiter? is it faster? does this show in images? if so are images that combine both jupiter and its moons showing a true representation of how large the moons are?
er... getting my drift? kinda having troubles explaining whats in my head...

this was bought up by a friend of mine who i showed some pics to. he asked "gee are the moons really that big?"

yours eternally in craziness
ving

[erick (Eric)]

show us the pics in question?

[iceman (Mike)]

It depends on which moon(s). Io moves the fastest, followed by Europa then Ganymede then Callisto (with respect to our viewing position).

Io moves faster than the rotational speed of Jupiter, so you really need to capture for a less time otherwise you can end up with a blurred or elongated moon.

The length of capture really depends on your focal length. For short focal lengths, say under 4500mm or so, there wouldn't be much rotation shown in over 3 or 4 minutes. At 9500mm FL, I capture for about 2:30 (45 seconds in each channel) and that's about the limit I can go, and even then there can be a 1 or 2 pixel shift required to align the red channel (captured first) with the blue channel (captured last).

[ving (David)]

and how about the rotation of the moons? does thier rotation speed show up?

thanks for the answers btw

[iceman (Mike)]

The moons rotation? You're not imaging at long enough focal length to worry about that I would imagine.

[[1ponders] (Paul)]

You don't have to worry about the moons' rotation ving. The 4 Galilean moons all have synchronous orbits.