Long post, transit of Venus 1882

Is it too early to start this thread ?

An account of the transit of Venus in 1882 by
Sir Robert Ball, LL.D. D.Sc.

From
THE STORY OF THE HEAVENS.
Cassell & Company Ltd.
London
1905

"...I venture to record our personal experience of the last
transit of Venus, which we had the good fortune to view
from Dunsink Observatory on the afternoon of the 6th of
December, 1882.
The morning of the eventful day appeared to be about
as unfavourable for a grand astronomical spectacle as could
well be imagined. Snow, a couple of inches thick, covered
the ground, and more was falling, with but little intermis-
sion, all the forenoon. It seemed almost hopeless that a
view of the phenomenon could be obtained from that observa-
tory ; but it is well in such cases to bear in mind the
injunction given to the observers on a celebrated eclipse
expedition. They were instructed, no matter what the day
should be like, that they were to make all their preparations
precisely as they would have done were the sun shining with
undimmed splendour. By this advice no doubt many ob-
servers have profited; and we acted upon it with very con-
siderable success.
There were at that time at the observatory two equa-
torials, one of them an old, but tolerably good, instrument,
of about six inches aperture; the other the great South equa-
torial, of twelve inches aperture, already referred to. At eleven
o'clock the day looked worse than ever; but we at once pro-
ceeded to make all ready. I stationed Mr. Rambaut at the
small equatorial, while I myself took charge of the South
instrument. The snow was still falling when the domes were
opened; but, according to our prearranged scheme, the
telescopes were directed, not indeed upon the sun, but to the
place where we knew the sun was, and the clockwork was
set in motion which carried round the telescopes, still con-
stantly pointing towards the invisible sun. The predicted
time of the transit had not yet arrived.
The eye-piece employed on the South equatorial must also
receive a brief notice. It will, of course, be obvious that the
full glare of the sun has to be greatly mitigated before the
eye can view it with impunity. The light from the sun falls
upon a piece of transparent glass inclined at a certain angle,
and the chief portion of the sun's heat, as well as a certain
amount of its light, pass through the glass and are lost. A
certain fraction of the light is, however, reflected from the
glass, and enters the eye-piece. This light is already much
reduced in intensity, but it undergoes as much further
reduction as we please by an ingenious contrivance. The
glass which reflects the light does so at what is called the
polarising angle, and between the eye-piece and the eye is a
plate of tourmaline. This plate of tourmaline can be turned
round by the observer. In one position it hardly interferes
with the polarised light at all, while in the position at right
angles thereto the tourmaline intercepts nearly all the light.
By adjusting the position of the tourmaline, the observer has
it in his power to render the image of any brightness that
may be convenient, and thus the observations of the sun can
be conducted with the appropriate degree of illumination.
But such appliances seemed on this occasion to be a mere
mockery. The tourmaline was all ready, but up to one o'clock
not a trace of the sun could be seen. Shortly after one
o'clock, however, we noticed that the day was getting lighter;
and, on looking to the north, whence the wind and the
snow were coming, we saw, to our inexpressible delight,
that the clouds were clearing. At length, the sky towards
the south began to improve, and at last, as the critical
moment approached, we could, detect the spot where the sun
was becoming visible. But the .predicted moment arrived and
passed, and still the sun had not broken through the clouds,
though every moment the certainty that it would do so
became more apparent. The external contact was therefore
missed. We tried to console ourselves by the reflection that
this was not, after all, a very important phase, and hoped
that the internal contact would be more successful.
At length the struggling beams pierced the obstruction,
and I saw the round, sharp disc of the sun in the finder, and
eagerly glanced at the point on which attention was concen-
trated. Some minutes had now elapsed since the predicted
moment of first contact, and, to my delight, I saw the small
notch in the margin of the sun showing that .the transit had
commenced, and that the planet was then one-third on the
sun. But the critical moment had not yet arrived. By the
expression " first internal contact" we are to understand the
moment when the planet ha-s completely entered on the sun.
This first contact was timed to occur twenty-one minutes
later than the external contact already referred to. But the
clouds again disappointed our hope of seeing the internal
contact. While steadily looking at the exquisitely beautiful
sight of the gradual advance of the planet, I became aware
that there were other objects besides Venus between me and
the sun. They were the snowflakes, which again began to
fall rapidly. I must admit the phenomenon was singularly
beautiful. The telescopic effect of a snowstorm with the
sun as a background I had never before seen.
It reminded me of the golden rain which is sometimes seen
falling from a flight of sky-rockets during pyrotechnic displays;
I would gladly have dispensed with the spectacle, for it necessarily
followed that the sun and Venus again disappeared from
view. The clouds gathered, the snowstorm descended as
heavily as ever, and we hardly dared to hope that we should
see anything more; 1 hr. 57 min. came and passed, the
first internal contact was over, and Venus had fully entered
on the sun. We had only obtained a brief view, and we
had not yet been able to make any measurements or other
observations that could be of service. Still, to have seen
even a part of a transit of Venus is an event to remember
for a lifetime, and we felt more delight than can be easily
expressed at even this slight gleam of success.
But better things were in store. My assistant came over
with the report that he had also been successful in seeing
Venus in the same phase as I had. We both resumed our
posts, and at half-past two the clouds began to disperse, and
the prospect of seeing the sun began to improve. It was now
no question of the observations of contact. Venus by this
time was well on the sun, and we therefore prepared to make
observations with the micrometer attached to the eye-piece.
The clouds at length dispersed, and at this time Venus had
so completely entered on the sun that the distance from the
edge of the planet to the edge of the sun was about twice
the diameter of the planet. We measured the distance of the
inner edge of Venus from the nearest limb of the sun. These
observations were repeated as frequently as possible, but
it should be added that they were only made with very
considerable difficulty. The sun was now very low, and the
edges of the sun and of Venus were by no means of that
steady character which is suitable for micrometrical measure-
ment. The margin of the luminary was quivering, and Venus,
though no doubt it was sometimes circular, was very often
distorted to such a degree as to make the measures very
uncertain.
We succeeded in obtaining sixteen measures altogether;
but the sun was now getting low, the clouds began again to
interfere, and we saw that the pursuit of the transit must be
left to the thousands of astronomers in happier climes who
had been eagerly awaiting it. But before the phenomena had
ceased I spared a few minutes from the somewhat mechanical
work at the micrometer to take a view of the transit in the
more picturesque form which the large field of the finder
presented. The sun was already beginning to put on the
ruddy hues of sunset, and there, far in on its face, was the
sharp, round, black disc of Venus. It was then easy to
sympathise with the supreme joy of Horrocks, when, in 1639,
he for the first time witnessed this spectacle. The intrinsic
interest of the phenomenon, its rarity, the fulfilment of the
prediction, the noble problem which the transit of Venus helps
us to solve, are all present to our thoughts when we look at
this pleasing picture, a repetition of which will not occur again
until the flowers are blooming in the June of A.D. 2004.
The occasion of a transit of Venus also affords an oppor-
tunity of studying the physical nature of the planet, and we
may here briefly indicate the results that have been obtained.
In the first place, a transit will throw some light on the
question as to whether Venus is accompanied by a satellite.
If Venus were attended by a small body in close proximity,
it would be conceivable that in ordinary circumstances the
brilliancy of the planet would obliterate the feeble beam of
rays from the minute companion, and thus the satellite would
remain undiscovered. It was therefore a matter of great interest
to scrutinise the vicinity of the planet while in the act of
transit. If a satellite existed-and the existence of one or
more of such bodies has often been suspected-then it would
be capable of detection against the brilliant background of
the sun. Special attention was directed to this point during
the recent transits, but no satellite of Venus was to be found.
It seems, therefore, to be very unlikely that Venus can be
attended by any companion globe of appreciable dimensions.
The observations directed to the investigation of the
atmosphere surrounding Venus have been more successful.
If the planet were devoid of an atmosphere, then it would
be totally invisible just before commencing to enter on the
sun, and would relapse into total invisibility as soon as it had
left the sun. The observations made during the transits are
not in conformity with such suppositions. Special attention
has been directed to this point during the recent transits. The
result has been very remarkable, and has proved in the most
conclusive manner the existence of an atmosphere around
Venus. As the planet gradually moved off the sun, the
circular edge of the planet extending out into the darkness
was seen to be bounded by a circular arc of light, and Dr.
Copeland, who observed this transit in very favourable
circumstances, was actually able to follow the planet until it
had passed entirely away from the sun, at which time the
globe, though itself invisible, was, distinctly marked by the
girdle of light by which it was surrounded. This luminous
circle is inexplicable save by the supposition that the globe
of Venus is surrounded by an atmospheric shell in the same
way as the earth..."


jc

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"John Carruthers" wrote:

The intrinsic
interest of the phenomenon, its rarity, the fulfilment of the
prediction, the noble problem which the transit of Venus helps
us to solve, are all present to our thoughts when we look at
this pleasing picture, a repetition of which will not occur again
until the flowers are blooming in the June of A.D. 2004.

HADAS will be doing a public presentation about transits on June 3rd
at Homewood School, anchored round the paragraph above.

It worries me that, given the absolutely central role of Horrocks and
Halley in bringing the significance of transits to the world , the UK
is doing next to bugger all about it, with the exception of David
Sellers and Alan Chapman. Tons of really good stuff on the web in
Italian, German, French and American but very little from us.

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

"Martin Frey" wrote in message
...

It worries me that, given the absolutely central role of Horrocks and
Halley in bringing the significance of transits to the world , the UK
is doing next to bugger all about it, with the exception of David
Sellers and Alan Chapman. Tons of really good stuff on the web in
Italian, German, French and American but very little from us.


www.transit-of-venus.org.uk

Robin

"John Carruthers" wrote in message
...
Is it too early to start this thread ?

An account of the transit of Venus in 1882 by
Sir Robert Ball, LL.D. D.Sc.

From
THE STORY OF THE HEAVENS.
Cassell & Company Ltd.
London
1905

snip

John

Would you mind if I posted a copy of that on my school's website, to accompany our
Transit page?

http://faxmentis.org home page, with indexes and frames and stuff

http://faxmentis.org/html/transit.html the Transit of Venus page, sans frames

Jeff
Parramatta High School
150°59'44"E 33°49'15"S

"Robin Leadbeater" wrote:


"Martin Frey" wrote in message
.. .

It worries me that, given the absolutely central role of Horrocks and
Halley in bringing the significance of transits to the world , the UK
is doing next to bugger all about it, with the exception of David
Sellers and Alan Chapman. Tons of really good stuff on the web in
Italian, German, French and American but very little from us.


www.transit-of-venus.org.uk

Robin

I think that's the reason I made Alan Chapman an honourable exception.
But a 140 pound academic conference doesn't begin to compare with say

http://www.transitofvenus.org
or
http://perso.wanadoo.fr/pgj/transit0...plications.htm

We have an educational opportunity of several lifetimes here and we
are blowing it. The great lakes planetarium near Chicago, where they
will only get the last few minutes of the transit at dawn, are putting
on a superb show and pushing out a dvd of the program so us schools
can get to grips with basic solar system astronomy in an immediate,
relevant and, dare I say it, exciting way.

All bitterly disappointing.

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

Would you mind if I posted a copy of that on my school's website, to
accompany our
Transit page?

Please do, that's what it's all about.

We, (SEKAS) will be on the seafront opposite Walmer castle on the day.
Hopefully the local press will give us as much support as they did for
the Mars apparition and the Mercury transit.
jc



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"A.Gent" wrote:


"John Carruthers" wrote in message
...
Is it too early to start this thread ?

An account of the transit of Venus in 1882 by
Sir Robert Ball, LL.D. D.Sc.

From
THE STORY OF THE HEAVENS.
Cassell & Company Ltd.
London
1905

snip

John

Would you mind if I posted a copy of that on my school's website, to accompany our
Transit page?

http://faxmentis.org home page, with indexes and frames and stuff

http://faxmentis.org/html/transit.html the Transit of Venus page, sans frames

Jeff
Parramatta High School
150°59'44"E 33°49'15"S

This passage is quoted all over the place on the web: I'm sure it will
be OK, given the author and publication dates being nigh on 100 years
ago. Most UK secondary schools have some sort of royaly license: costs
a bit but covers you for most uses of material a school might want.Bet
you have similar scheme in Oz.

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

"Martin Frey" wrote in message
...
"A.Gent" wrote:


"John Carruthers" wrote in message
...
Is it too early to start this thread ?

An account of the transit of Venus in 1882 by
Sir Robert Ball, LL.D. D.Sc.

From
THE STORY OF THE HEAVENS.
Cassell & Company Ltd.
London
1905

snip

John

Would you mind if I posted a copy of that on my school's website, to accompany our
Transit page?

http://faxmentis.org home page, with indexes and frames and stuff

http://faxmentis.org/html/transit.html the Transit of Venus page, sans frames

Jeff
Parramatta High School
150°59'44"E 33°49'15"S

This passage is quoted all over the place on the web: I'm sure it will
be OK, given the author and publication dates being nigh on 100 years
ago. Most UK secondary schools have some sort of royaly license: costs
a bit but covers you for most uses of material a school might want.Bet
you have similar scheme in Oz.

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

Thanks John, Thanks Martin.

I'll post it this week.
...and yes, we do have just such a copyright/ royalty scheme.

-- praying for a clear day --

Jeff

"John Carruthers" wrote in message
...
Would you mind if I posted a copy of that on my school's website, to
accompany our
Transit page?

Please do, that's what it's all about.

We, (SEKAS) will be on the seafront opposite Walmer castle on the day.
Hopefully the local press will give us as much support as they did for
the Mars apparition and the Mercury transit.
jc

Thanks John.
...and speaking of Mercury: http://faxmentis.org/html/science36.html

Cheers from the Southland
Jeff


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"A.Gent" wrote:

Thanks John.
..and speaking of Mercury: http://faxmentis.org/html/science36.html

Cheers from the Southland
Jeff

Your website mentions the awful termination of the Venus transit in
mid flight - hehe we get it all! (Last time we could have seen it all
William Wallace aka the ghastly Mel Gibson's Braveheart was 11)

BUT the boot will be on the other foot in 2012 - you will be on one of
the very few landmasses to see it all, along with Japan, China,
Siberia and Alaska. All we get is the tail end at dawn.

http://www.imcce.fr/ephem/passage/dessins/Venus2012.jpg

Observatoire de Paris - another good transit site and the best
daylight maps I've seen thanks to Patrick Rocher.

(Talking of which, I saw the 99 solar eclipse in France in a field
next to a party from the Paris Observatory, including an American
post-grad. He was absolutely astounded by the coincidence that the old
French meridian 0 ran slap dab through the centre of the observatory -
so I said strange, the Greenwich meridian goes through an observatory
in England too. Merkins.)

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47