Re: Satellite observing

Bjoern Gimle (
Sun, 12 Apr 1998 00:03:41 +0200

>> To:

"Sue J. Worden" <> wrote:
>> the shadow height has to be "just right".  This happy medium can occur
>> all night at moderately high latitudes during local summer.  For example,
>> at 50 degrees North latitude, at summer solstice, the shadow height grows
>> very slowly, taking about two hours following sunset to reach the 60 mile
>> height, which marks the end of twilight and start of the viewing period.
>> However, for the rest of that night, the shadow height never grows beyond
>> about 160 miles.  Since almost all satellites orbit the Earth at altitudes
>> greater than 160 miles, the viewing period effectively lasts all night in
>> this case.
>> I don't know whether there are other effects that could make May "special"
>> in terms of watching satellites.  I'm forwarding a copy of this message
These arguments assume you are watching satellites directly overhead.
Then the satellites at the same height in the direction opposite to the
Sun, where the best lighting conditions appear, are occulted.

On the other hand, in the Summer you can see satellites at higher latitudes,
for a longer period. At 10 degrees further away from the equator, many
satellites above 200 miles can still be seen from your latitude.

This means that "in May" you can enjoy the long twilight of the northern
latitudes, while you are in a relatively dark night.

At these higher latitudes, the longitudes are a bit closer to each other, so
more passes per night may be within range.

And all satellites make a smaller angle with the longitudes, some even go
due West-East at those latitudes, so even more passes are visible per night.

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