From: FrankEReed@aol.com
Date: Thu Feb 17 2000 - 20:32:00 PST

• Next message: Bjoern Gimle: "Re: shuttle radar visible ("Polar" alignment)"

```Me earlier:
"Also, align your telescope's mounting so that you are mostly slewing  in one
dimension --makes it much easier. Think of the satellite's path
across the sky as an approximation to a great circle. Point one axis of the
scope's mounting towards the pole of the great circle."

I think I can put this in more practical terms. Find the point of max
elevation. Point one axis of the telescope to the spot in the sky that is 180
degrees away from that point in azimuth and complementary to it in altitude
(90-max altitude). An example: suppose the satellite you're chasing reaches
max altitude at 70 degrees in the northeast (azimuth=45). Point one axis of
your mounting towards the southwest at an altitude of 20 degrees. This will
generally align motion about that axis along the path of the satellite so
that you only have to slew in one dimension. And don't just think in terms of
the polar axis of your mount. You can pick either axis based on what's
physically convenient with the mount of your scope.

By the way, this trick also applies to chasing very faint satellites. If
you're hunting something at, say, tenth magnitude, and the orbital elements
are good, you can point the scope at exactly the right spot and wait. When
you see it zip across the field of view, you'll want to chase it, but it's
easy to get ahead or behind and lose such a faint object. If the scope is
aligned to slew approximately along the path, you'll be able to sweep it up
again in many cases.

-Frank E. Reed
Chicago, IL

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