transits of mir/sts

From: Robert Preston <>
Date: Wed, 15 Mar 1995 14:33:41 -0500

I read Walter's post with great interest, since I have been thinking
about looking for these phenomena myself, eventually to photograph the
events. I have been using the Power Macintosh- based SkyChart2000,
by Tim Benedictis, which inputs TLE's and will do a search for minimum
angles between any two objects. I've not done a great deal of work on this
yet, but I think the program did successfully predict a Mir/Lunar transit
when I tried it several months ago. I was tracking the near-full moon with
a Meade 8" LX200 during the predicted transit, using a 72X power that
included the whole moon in the field of view. As I recall, within two
minutes of the predicted transit time, I saw an object (which I like to think
was Mir!!) zip across the field of view in about a third of a second, the
expected transit duration. Obviously this might have been a terrestrial
insect or bat, too...I've not had an opportunity to repeat the attempt since
that one time. I have an extreme-wide-angle 220x eyepiece that should give
nice resolution of the general shape of Mir or STS, without requiring
extreme accuracy of coordinate prediction, but the experiment needs still
to be done. I also have an idea for a simple Mir-tracking system for the
LX200, but that needs further work before I can crow about it.

I don't understand the table posted by Bjorn Gimle, I must say...the
meanings of the various columns escapes me, and it seems that he has
predicted several solar transits in one day??? that seems unlikely,
statistically. I must be misinterpreting the data.

The SkyChart2000 search for transits takes only a few seconds per
conjunction, but the distances in most conjunctions are too large to
give transit. I'm trying to convince Tim to add code to tell it to find
only transit-type conjunctions (distances predicted as less than one-quarter
degree), so that would give a much faster, automatic search. As it is, it
takes a half-hour to wade through all the conjunctions manually. If it
were automatic, I'd guess it would only take a minute or two to search the
orbit forward for two or three days. Beyond that, the TLE is likely to be
different anyway, from thrusters or air frictional changes.

Robert Preston                          
University of Pittsburgh                        Pittsburgh PA 15261
Received on Wed Mar 15 1995 - 14:55:10 UTC

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