Hubble question

Sorry for the OT question, but this has been nagging me for some time.

Hubble is in orbit around the earth, and as such, travels at a great
speed as well as constantly changing its direction of travel (nature of
a circular trajectory).

How does it take pictures of very faint objects without having any blurr
due to its movement or change in orientation due to its orbit ?

Or is its CDD sensor (or whatever technology used to capture images) so
sensitive that it only needs a very short exposure time to capture those
images and thus the speed of Hubble is of no consequence ?

"John Doe" wrote in message
...
Sorry for the OT question, but this has been nagging me for some time.

Hubble is in orbit around the earth, and as such, travels at a great speed
as well as constantly changing its direction of travel (nature of a
circular trajectory).

How does it take pictures of very faint objects without having any blurr
due to its movement or change in orientation due to its orbit ?

Just because an object is in orbit does not necessarily mean that its
orientation is fixed with respect to the earth, it's path around the earth,
and etc. But it is noted that objects in earth orbit do encounter forces
which do tend to change their orientation. These include gravity, drag
(there is still a tiny bit of air up there), magnetism (earth's magnetic
field), solar effects, and etc. So, in light of all of these forces, Hubble
needs a way to counteract them.

To this end, Hubble has an extremely sensitive pointing system, so it can
remain pointed at a target for very long periods of time, which enables it
to take very long exposure pictures. You ought to be able to find more info
about this system by Googling for "Hubble gyroscopes " or something like
that.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein