Re: A few questions from a beginner.

Bart De Pontieu (BDP@MPEPL)
Wed, 28 Aug 1996 13:46:34 +0100 (CET)

Willie Koorts writes:

>Someone mentioned about software which would modify your QUICKSAT.MAG file
>with information such as classes of objects,  comments,  etc to tailor it
>to be used for selective selections when predicting for BWGS observations.
>What was this program called?  What format of file is needed to feed this
>program with information to do these modifications?

This program is called XFROB, written by Mike McCants. It is available at 
the SeeSat-L e-mail archive in uuencoded and zipped form. Send a message with
SUBJECT: archive get quicksat/xfrob.uu
to SeeSat-L-request@iris01.plasma.mpe-garching.mpg.de
to get the program. The zip-file contains an executable for PC, but the 
fortran-code is also available, and I've compiled it without problems on
unix-machines.
 
XFROB needs two input files :
  MAG.IN : a normal quicksat.mag file (also available in the quicksat-dir)
  ROB.IN : a ROB program file of the BWGS

The ROB-file is available by sending a message with this command: 
archive get program/program.rob
It is also available at ftp://ftp.physics.ox.ac.uk/pub/sat/bwgs
where it is updated monthly.

XFROB produces one output file :

  MAG.OUT

which is a new quicksat.mag file. This file
contains :

- all BWGS satellites from ROB.IN
- international designation from ROB.IN
- flash period comments from ROB.IN
- 'B' flag for the BWGS-satellites

You can then use the 'B' flag to predict BWGS-program satellites.
It works very well. The only problem that sometimes can occur is that the
program.rob file contains satellites of which the NORAD-no. is not known
yet at the time the program is compiled/edited.

>Then I have a more practical question for all you experienced BWGS observers
>out there. In the PPAS format, cols. 19-28, where one reports the end time of
>an observation,  the recommended format is hh:mm:ss.t.  How can one know this
>time so accurately when using a stopwatch?  

I think the way people do this is by stopping (or starting) their stopwatch
on a known time-signal they pick up from radio, etc. I know that in the
Benelux many observers have clocks with a built-in radio receiver that is
tuned to a radio station that sends out time signals (DCF-77 at 77.5 Khz ?).
The Internet is apparently also a possibility, as evidenced by Jim Varney's
message recently.

>Do one need a special type of stopwatch to achieve this?  
>All stopwatches I know loose the absolute time
>display when put into stopwatch mode.

I've never seen a stopwatch that has absolute time at the same time as
the stopwatch mode either.

>Another practical question.  First a little background.  I made myself a
>sort of "theodolite" using two protractors ( 360 deg. for Azimuth and 90
>deg. for Altitude) to be able to find satellites.  To use it, I would park
>my telescope/monocular at an Alt/Az position along the track of the
>satellite I want to observe and wait till the predicted time for it to
>cross the FOV whereafter I start tracking it.  If it goes too far over the
>time and I have not seen it yet, I would advance the mount to a higher
>point along the track and try again.  Depending on the sky conditions, I
>managed about a 60% hit rate when I was using a 35mm refractor with a 5
>deg. FOV.  I have just recently modified a 80mm spotting scope to a right
>angle eyepiece giving me about a 4 deg. FOV.  I seem to be able to find
>about 85% of predicted BWGS satellites ( selecting the b & ! classes )
>with this setup.  Any practical suggestions on how I could improve my hit
>rate with this system? 

One option would be to aim one of the axises of your telescope towards the
pole of the satellite's orbit, *as seen by the observer* (this one had me
fooled back then, hence the emphasis). This means you then just have track 
on one axis, which seems easier to do. There was a discussion about this 
technique on SeeSat in June 1995. Messages old1/470, old1/476, old1/477, 
old2/507, old2/510, old2/517.
Message old2/574 contains Bjoern Gimle's routine to calculate the pole
(written in basic).

Note that our e-mail archive is subdivided in 6 subdirectories: old1,
old2, old3, old4, old5 and latest
old1 contains message 1 to 500, old2 has 501 to 1000, etc.
The old-directories are regularly added to empty out the 'latest' directory.
The wearisome subdivision into 'old'-directories is not just there to bug you.
It is necessary because of limitations on the CPU-time archive jobs can
have. Searching through the archive can be done with the command 'egrep'
which can be pretty CPU-thirsty.

Cheers,
     Bart
-------------------------------------------------------------------------------
Bart De Pontieu --  Max-Planck-Institute for extraterrestrial Physics, Garching
bdp@mpe-garching.mpg.de  --      http://www.rzg.mpg.de/~bdp/satintro.html
Join us at Eurosom 2, Oct 19/20 1996 -- http://www.rzg.mpg.de/~bdp/eurosom.html
BWGS-coordinator -- Flash editor -- SeeSat-L administrator -- would-be-observer
   "Life is like a jigsaw. You get the straight bits, but there's something"
       "missing in the middle." -- XTC, "All Of A Sudden (It's Too Late)"
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