Transit observation

Rob Matson (
31 Jul 1996 10:12:58 -0800

                      Subject:                              Time:  09:34
  OFFICE MEMO         Transit observation                   Date:  96/07/31

In case any other Seesat-L'ers had an interest, I thought I'd share this
recent exchange between me and Willie Coorts:


On Tuesday July 30, Willie Coorts wrote:

... We have an old solar telescope on site which projects a 10" solar
image onto a ground glass screen.  The telescope aperture is not that
big though, about 3" maybe.  People photographed this screen before,
showing sunspots or eclipses.

I ran Skymap in its transit mode and tried looking for the sats passing 
across the disk of the sun.  I had no luck yet.  I realised that I needed very
accurate elements and should rather target only a few selected sats, perhaps
ones with stable orbits and of fair size.  I have a video
camera at home or if I am quick enough,  might be able to take a 
photo with a camera on a tripod.

To which I replied:


I ran a prediction for your location using the largest 30 satellites, and I
came up with only one transit for the next week.  It's a grazing transit on
July 31 at 10:14:00 local time (GMT+2 hours) by Cosmos 2263 R/B (#22803).  The
elements I have are from 7/23 -- a week old, so it may miss.  Or who knows? 
Maybe it will improve and be more central.  As it is, it'll graze the left
edge of the sun around the 10 o'clock position as you look at the sun.  (You
can check it out with SkyMap, of course.)

And today, Willie replied with this pleasant surprise:

Hi Rob

Thanks a million for the prediction - I SAW IT!!!!!!!!!!!!!!!!!!  and it 
was GOOOOOOD :-))))))))

I made sure the telescope was tracking on the Sun well before the time. 
BTW there is a nice sunspot group that just recently rotated into view.  A few
others who were interested joined as the time came closer (what makes you
think the boss is off-sick today?).  Because the telescope is on an equatorial
mount, I could not easily relate your directions of position angle to where I
should expect the pass.  I also did not have a clue to what size of object and
speed accross the disk to expect. 

Because we were four people, I was still explaining that we should have
divided the disk up into 4 and each person scanning one quarter, when it
happened!  A blob as big as my little finger (bigger than the whole sunspot
group) zoomed across the disk about 1/4 in from the edge at one heck of a
speed - it could not have spent more than 1/10 sec. on the disk.  I could
swear I saw a shape like a cylinder slightly off from edge-on - bit it could
be just my imagination because it was very quick.


Now I want to first see if I can repeat this prediction for myself and 
then bring in my video camera to work when there is one again.
Thanks for the list of targets as well.  I should get my 9" telescope at home
fitted with a filter and try some 
over weekends as well.

This is really good fun!

Thanks again.

Willie Koorts