HOW I TRACK THE ARTIFICIAL SATELLITES WITH MY TELECOPERetour page principale
EXAMPLE OF WHAT CAN BE SEEN AT THE SCREEN OF THE PC:
I often make demonstrations of the system I use to aim my telescope onto a point where a satellite should pass and then track it.
In August 1992 (night of the 4th to the 5th), with five specialists, near my house of Esparron in Provence, we could use that system and track 21 satellites during the same night.
The last one was the rocket of COMSTAR 4 which was 25,000 Km far and gave a flash every 40 sec.!
The telescope is a NEWTON D=130 mm F=720 mm on an ALT-AZ. MOUNT.
The 2 motions (alt. and az.) are controlled by step-motors and my computer.
On the same mount, I sometimes fit a CCD VIDEO CAMERA (6 mm x 4.5 mm matrix) with an russian objective F=85 mm 1/f=2. I can with it record the passages on tapes.
At a meeting in Loon-op-Zand, I could show on such a record-tape the flashes of COBE.
One can also fit on the same mount binocculars, other optics, and so watch at the satellite with several people.
You can find an article about my works in S&T of august 1993 :"My robotic AstroScan".
I could record a passage of MIR when the Sun was only 1 deg. under the horizon! At the end of that passage, it's very interesting to see MIR amongst the branches of a tree. MIR remains centered in the TV screen, appearing and disappearing behind the moving branches.
To prepare an observation night, it takes me now less time than to write these explanations...
1) By means of a first program, I make a selection of the satellites I want to know if they will be visible, when and where.
2) By means of second program, for all the satellites of my selection, I create a file in which are the instants of visibility with Az., Alt., Alt.Sun, Hgt., Dist., and the current magnitude if out of earth's shadow.
3) By means of a third program, I can easily choose for each satellite the instant I want the tracking to be started according to alt. and az. The same program makes a file which will be used by the computer during the session of observation: The chosen instants are sorted chronologically. The direction of the satellite is given by means of Increasing or decreasing azimuth, increasing or decreasing altitude".
Those three things takes me less than 20 min. for one night and up to 100 (one hundred) satellites.
I make the setup of my telescope in 5 minutes because it is an ALT.-AZ. mount.
I use therefor a spirit level, fixed on the top of the mount.
If the level is horizontal for any azimuth it means that the main axis (azim-axis) is vertical.
As you can see in the article of S&T, I tried several kinds of mounts, even a spheric one for the AstroScan.
At my opinion, the alt-az mount is the most convenient
for several reasons at the contrary of an equatorial mount
or a mount centered onto the center of the satellite curve:
1) It's very easy to balance. So it can support several
2) With a Newton telecope, the eye-piece is always horizontal. No need of ladders, steps, leg motions, etc.
3) It's easy to reach any point of the sky from
0 to 90 deg. altitude in any azimuth.
4) The setup can be made anywhere, even in day-light, in a few minutes. No need of Polaris or Bigourdan.
5) Even without the control of the step-motors by the
computer, it can be used the following way: A lot of prgrams
give alt. and azim. So by means of the graduation circles,
it's easy to aim the telescope onto the right point of the
sky where the satellite will be passing.
Everything I use (Computer, step-motors, camera, recorder,
etc...) is on 12v cc. So, if my car is not too far, I don't
need the main 220v current.
The screen of the computer gives me in graphics
(like with "LOGIS-CIEL") the aspect of the current sky,
centered on the location where the first satellite
is expected. I choose a known star for initialization.
The screen gives also the remaining time in minutes and,
if I want it, a list of interresting things to be seen
while waiting (M31, M13, Albireo, etc...)
So in the mean-time, I can aim automatically the telescope
in order to allow my friends to admire what they want.
When it remains only 5 minutes for the passage of the
expected satellite, the computer beeps.
Then I ask it to aim onto the the point where the stellite
will be passing. When aimed there, the telescope does't move
anymore. Everybody is at his ocular. One of us has in his
hand a kind of "track-ball" which will allow him to start
the tracking when the satellite will appear in his field.
The computer beeps on a frequency. For the 60 last seconds,
another frequency, for the 10 lest seconds, another one,
suspense...! at the predicted instant, another beep.
So it's easy to see if the satellite is ahead or delayed.
The same track-ball gives the possibility to make
corrections if the satellite is not well centered in the
Another program is also very interresting.
One night, we were tracking a satellite with Mr Paul
PAQUET, the director of the Belgian Royal Observatory.
As the satellite remain centered, the celestial objects
are passing in the ocular. We could see a planetary nebulae
passing. Later on, when our observations were finished,
we used then another of my programs to identify it.
That program shows the sky in graphics (like with "LOGIS-CIEL"),
stars up to magnitude 5, moon (with its phase), planets
and the 110 Messier objects. But also the satellite moving
amongst them! And it's very easy to identify any object near
which it is passing.
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