Ident please ?, also SL16,Iridium30

Malcolm Purves (
Sun, 22 Aug 1999 01:25:16 +0100

Hello, apologies in advance for a long and rambling post to ask two
questions :-

I am new to the list ( subscribed at the end of July ) and I have been
most interested in all that you have been doing.
I would normally 'lurk' for a bit longer before posting, however I have
just had a most entertaining session this evening with the flasher
SL-16 #25861 which Ron Lee and others commented upon a couple of days
ago and also a very bright ( predicted -8 by iridflare165 ) flare by
Iridium 30.
My reason for posting is that I saw a satellite in the right general
area a minute or so before the predicted time for the SL16 but not
flashing. Huh! I thought, so much for that damp squib ! Got my
prediction wrong and it didnt flash, can I have my money back ! :-))
However, following it for a short while it didn't have the expected
trajectory so I noted the following :
On a South to North pass, elevation about 45deg in the West at the
start. It passed below the head of Draco, passed by theta Draco
missed gamma Ursa Minor by a very close shave just below, and was by
then dipping down rapidly close to the right (North) of beta U.Minor
At this time it either lost illumination or went behind a cloud! The
sky in the West had high haze and streaky cloud so seeing was not good
and the moon was up. Brightness was about the same as the peaks of
SL16, which passed by right on schedule shortly afterwards!
Sorry for the lack of timing precision and the vagueness of the initial
sighting but as I am just getting up to speed with this satellite
observing lark I was just there for the curiosity and interest, not
for any science !
The pass of the SL16 that I was observing was for this prediction
by Quicksat :-
  51.444   2.745  250.                            2000  6.5 15 F T T T T
 ***  1999 Aug  21  Sat evening  *** Times are PM BST  ***  2128  459
  H  M  S  Tim Al Azi C Dir  Mag Dys F  Hgt Shd  Rng  EW Phs  R A   Dec
 25861 Okean-O r     
22 14 30   .0 45 209    48 20.4   9 5  420 238  567 1.3  68 1741   9.5
22 15 37   .0 58 261 C  92 20.3   9 5  420 302  487 1.3  94 1617  37.6
22 16 45   .0 44 311   133 21.2   9 5  420 352  578 1.0 120 1331  56.6

and Long 2.745 West, there may be some uncertainty in the last digit!
I.e. SW England , West of Bristol. BST being of course +1 on UT.

When the SL16 came along I called out my wife and she was suitably
impressed by the sight of this tumbling rocket body.

My second and more significant puzzle was soon after this.

Expecting a -8 flare off Iridium 30 I thought it worth keeping my wife
outside a bit longer :-) in the hope that this would impress her also !
Thus :-
      Local    Local     Iridium          Sun    Flare  Max Flare  Ird
Day   Date     Time    Azm El Rnge N I  Azm Elv Mag MMA  Bearing    # 
Sat 99- 8-21 22:34:30  052 36  758 D L  319 -17  -8  R   2.8 mi E  30   

Whilst we waited I pointed out the stars of Cassiopeia, Cygnus etc. to
her and shortly before 22:34 I had this :
Going North to South between gamma and delta Cygnus, then passing
between eta and beta Cygnus, a very bright flashing 'thing' !! more
or less overhead.
"Oh ! what,," I said, as my wife gave a gasp, as this 'thing' slowly
flashed in and out of sight, getting brighter with each flash. Is it
an aircraft we said to each other, no noise, no other lights red or
green. Never seen an aircraft strobe that bright,not underneath it
and not landing beside us!  not bright enough to cause exclamations !
The flashes became not so bright as it headed for Aquila.
Humm, I said to her, must be an aircraft because for a satellite to
flash that bright it cannot be in a high orbit ( my poor little brain
was doing overtime ! ) and if it isnt in a high orbit it shouldnt be
illuminated by the sun by now,,, 
with that it vanished ! close by Altair, alpha Aquila, to the South.
I am not good with magnitude estimates, made worse by the thing
flashing like that, but it was a lot brighter ( so quick and sharp that
it could be described as intense, in fact just like a strobe ) than
Vega, not so bright (perhaps ! ) as the Iridium flare that came along
shortly, 1 or 1&1/2 minutes, later. Ok, so it was near the zenith in
darker sky than the Iridium so what shall we say -4 +- a bit ? I
wish Venus had been about, it could have been comparable, I am not sure.

Again, any guesses please.

It would add to the pleasure of the evening if we could get an ident
on these, and follow them again sometime, but because of my lack of
observational experience and precision I am doubtful, but perhaps you
wizards might be able to come up with something ?

Thanks for a most interesting list.