Bruno Tilgner (Bruno_Tilgner@compuserve.com)
Sat, 11 Sep 1999 17:08:55 -0400

Jonathan Dietrich wrote:

>I observed Mir this morning.  I have never seen a satellite do what it did
>this morning - it seemed to deviate from its path, almost undetectably -
>sort of like it was wavering back and forth like a very shallow sine wave.
>Was this an optical illusion or did I actually see it happen?

There has been a discussion here on SEESAT on this subject two or three
years ago. As far as I remember, the consensus was that this is an
optical illusion. The actual meandering is caused by atmospheric

Funny enough, I have just received a CCD image which shows exactly this
sine wave pattern. In this case it cannot be an illusion, but there is
no plausible explanation either.

> This is probably a dumb question, ...

Not at all. There are no dumb questions, only dumb answers.

Bruno Tilgner