TRANSITS
Alphonse POUPLIER (alphonse.pouplier@skynet.be)
Thu, 8 May 1997 13:23:58 +0200 (MET DST)
Dear Friends,
I find the discussions about the solar transits very exciting.
I sent the text of the some messages to Jean BOURGEOIS (a very well known
and very serious observer) who could observe sat-transits
according to my predictions, including a geostationary.
His answer is given at the bottom of this message.
I'm prepared to make predictions of transits with a program I made
for 80 sats having
1) large dimensions 2) a good stability 3) a convenient distance.
I can do it for the interested SeeSatters having a good equipment
for such observations and being really experienced.
They should give me:
- the exact location of the observation site (latitude and longitude)
- the period to be analysed (from one date to another, one month maximum)
Here is the Jean Bourgeois's answer:
==============================================================
It is true that a spot with a size of less than one arcsecond
is not easy to observe on the Sun's surface, particularly
with the little apertures usualy used for solar
observations and the poor seeing we often meet in daytime,
but we need to consider a contrast effect that might enhance
our perception of little sized spots. The experience shows we
easily perceive nice details in the solar granulation,
although the contrast of these features is very low. An
enhancement of the contrast would allow the observer to catch
them more obviously. A satellite transit is an event with the
highest possible contrast, and I should not be astonished one
could see "dots" whose apparent dimensions are very faint.
Imagine a satellite transiting with an apparent size of 0.3
arcsecond. As we are looking at the dark side of it, the
contrast between itself and the solar surface is 100pc. If
the resolution of the image, considering our instrument and
atmospheric effects, is only 1 arcsecond, we should be able
to see the satellite as a spot of 1 '', with a contrast of only
0.3*0.3=0.09 or roughly 10pc. I am convinced we should be able
to detect such a low contrast little spot. Moreover, as this
spot should be moving onto the Sun, there is another factor
that can improve its detection.
Only repeated experiences can give us the right conclusion,
and I hope Alphonse POUPLIER will continue to distribute his
transit predictions to interested observers over the World.
Jean BOURGEOIS
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My pleasure, avec plaisir, Alphonse
alphonse.pouplier@skynet.be
URL:http://users.skynet.be/alphonse/
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