QUESTION:
Does the distance of an object from the infrared telescope affect 
the accuracy?

ANSWER from Scott Sandford on November 8, 1995:
There are several ways to answer this question depending upon what sort of
accuracy you are talking about. One type of accuracy astronomers worry about is
"positional" accuracy. This has to do with how certain you are about the exact
position of an object in the plane of the sky. Much of an astronomer's ability
to measure positions accurately depends on the telescope being used. Some
telescopes can be pointed at positions in the sky better than others an can
therefore make more accurate position measures. Also, telescopes can have the
problem of 'wiggling' or 'vibrating' when they are in use and this makes the
image of the object being studied appear to jump around. This makes it
difficult to measure the object's position very precisely. The 'wiggling' can
be due to anything from wind (or in California, earthquakes!) shaking the
observatory to the telescope warming up or cooling down. These problems are
associated with the telescope and have nothing to do with the distance to the
object being studied. The position of the object also appears to jump around
because air moving in the atmosphere 'bends' the light coming down from space.
This is the same process that makes stars appear to twinkle when you look at
them. Again, this process doesn't depend on the distance to the object.
Finally, the position of an object may be hard to determine accurately because
it is so dim that it is even hard to detect. If an object is hard to detect
reliably then it is also very hard to determine its precise position. The object
may be dim because it is intrinsically dim (like a firefly up close) or because
it's bright but very far away (like a bright light bulb 50 miles away). So, in
this case the distance to the object can have an effect on determining
positional accuracy. Thus, positional accuracy is a function of a number of
things, some of which depends on the distance to the object and some of which
don't.