Transit of Venus
jsp
Venus will move across the face of the Sun on June 8 (June 7 for the Western US)
for the first time in 122 years!
For information, see
http://www.jupiterscientific.org/sciinfo/astronews.html#venustransit
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Jupiter Scientific -- dedicated to the promotion of science
and scientific education through books, the internet,
and other means of communication
http://www.jupiterscientific.org
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Thomas D. Ireland
Http://www.rainbowsymphony.com/solar glasses
You can buy glasses anytime but I am not sure of the minimum quantity.
Good Luck!
Tom
jsp (jupiterscie...@yahoo.com) wrote:
: Just a reminder:
: Venus will move across the face of the Sun on June 8 (June 7 for the Western US)
: for the first time in 122 years!
: For information, see
: http://www.jupiterscientific.org/sciinfo/astronews.html#venustransit
: --------------------------------------------------------------
: Jupiter Scientific -- dedicated to the promotion of science
: and scientific education through books, the internet,
: and other means of communication
: http://www.jupiterscientific.org
: ```````````````````````````````````````````````````````````````````````
--
Alexander Naismith
"jsp" <jupiterscie...@yahoo.com> wrote in message
news:d09f31ec.04060...@posting.google.com...
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Henry
news:ca1c2j$qj9$1...@hercules.btinternet.com...
> I saw it last time - it was rubbish
>
Ssh, don't tell anyone - youre dead!
Adam Russell
it would pass us about every 1.6 years. Is it not on the same ecliptic or
something?
Howard Lester
"Adam Russell" wrote
> Why are venus eclipses so rare? A venus year is 225 days so I would think
> it would pass us about every 1.6 years. Is it not on the same ecliptic or
> something?
The path of the Sun (Marty) defines the ecliptic (the path where eclipses
can occur); all other bodies are either on it (but they cross it at some
point) or they're not. Venus's orbit is therefore somewhat inclined to the
ecliptic, as is the Moon's.
Howard (neither a cross-poster nor cross-dresser) Lester
Ugo
news:2ijl7qF...@uni-berlin.de...
> Why are venus eclipses so rare? A venus year is 225 days so I would think
> it would pass us about every 1.6 years. Is it not on the same ecliptic or
> something?
No, its orbit is tilted with respect to our ecliptic. Since from Earth we
see the Sun as an object only about 1/2 of a degree in diameter, even a
small tilt of Venus' orbit brings Venus "above" or "below" Sun's disc when
it passes us. For the very same reason the Moon doesn't eclipse the Sun
every month - its orbit is tilted about 5 degreees, IIRC.
--
The butler did it.
randyj
> it would pass us about every 1.6 years. Is it not on the same ecliptic or
> something?
>
passes us, but usually above or below the sun.
rj
Ugo
news:ca29gs$111u$1...@spnode25.nerdc.ufl.edu...
No, looks like you did your math upside down. Did you forget that the Earth
is also spinning around the Sun so Venus actually has come catching up to
do?
Mauritz Geyser
very old!!
"Thomas D. Ireland" <ug...@vtn1.victoria.tc.ca> wrote in message
news:40c4...@news.victoria.tc.ca...
randyj
"Ugo" <ugorda...@yahoo.com> wrote in message
news:ca29nn$o2i$1...@bagan.srce.hr...
oh yeah, actually i didn't do any math ;-)
i was just thinking about Venus having almost 2 apparitions a year,
once in evening, once in morning
rj
Henry Spencer
It's not. Venus's orbit is tilted about 3.3deg to the plane of the
ecliptic (Earth's orbit). An inferior conjunction -- when Venus passes
*close* to the Sun-Earth line -- does indeed happen about once every 1.6
years. But since the Sun seen from Earth is only about half a degree
wide, Venus needs to pass within a quarter of a degree of the Sun-Earth
line to actually cross the face of the Sun. That happens only when an
inferior conjunction occurs very close to Venus's line of nodes (where its
orbit plane intersects the ecliptic). More usually, Venus passes north or
south of the Sun.
Five inferior-conjunction periods is *almost* exactly eight Earth years.
Were that equality exact, inferior conjunctions would always happen in the
same five places around Earth's orbit, and if one of them wasn't very
close to Venus's line of nodes, we'd never see a transit. Since it's not
quite exact, those five places slowly drift around Earth's orbit. Around
the time one of them passes the line of nodes, we can see transits -- one
or two, depending on the exact timing. This time, we get one tomorrow and
one in June 2012.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert | he...@spsystems.net
Prai Jei
message <ca1c2j$qj9$1...@hercules.btinternet.com>:
> I saw it last time - it was rubbish
>
Last time was in 1882. How old are you? Or have you got it muxed ip with
last year's transit of Mercury?
--
Paul Townsend
I put it down there, and when I went back to it, there it was GONE!
Interchange the alphabetic elements to reply
Prai Jei
<HyyCC...@spsystems.net>:
> Five inferior-conjunction periods is *almost* exactly eight Earth years.
Fibonacci's Series rules OK :) The same period is almost exactly 13 Venus
years.
Brian Tung
Paul Townsend wrote:
> Last time was in 1882. How old are you? Or have you got it muxed ip with
> last year's transit of Mercury?
Maybe his name is really *James* Naismith.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
Alexander Naismith
I was watching an interview on TV tonight (UK) of an astrologer. Apparantly
we are in for 6 years of peace love and prosperity just because of this
transition. Oh yes and no possibility of a recession - looks like time to
start that small business up.
"Mauritz Geyser" <maur...@iafrica.com> wrote in message
news:40c4a...@news1.mweb.co.za...
Mark Earnest
"Prai Jei" <pvsto...@zyx-abc.fsnet.co.uk> wrote in message
news:ca2lvr$o48$1...@news6.svr.pol.co.uk...
> Alexander Naismith (or somebody else of the same name) wrote thusly in
> message <ca1c2j$qj9$1...@hercules.btinternet.com>:
>
> > I saw it last time - it was rubbish
> >
>
> Last time was in 1882. How old are you? Or have you got it muxed ip with
> last year's transit of Mercury?
He must be one of the immortals.
md
"Prai Jei" <pvsto...@zyx-abc.fsnet.co.uk> wrote in message
news:ca2lvr$o48$1...@news6.svr.pol.co.uk...
> message <ca1c2j$qj9$1...@hercules.btinternet.com>:
>
> > I saw it last time - it was rubbish
> >
>
> Last time was in 1882. How old are you? Or have you got it muxed ip with
> last year's transit of Mercury?
uh, me thinks he was joking....
Saul Levy
transit. The Sun isn't up that early and it still occurs only on June
8th. Nothing is happening today (the 7th).
The westernmost city listed in Sky and Telescope's coverage is
Houston, Texas where the transit ends just after sunrise.
Saul Levy
On 6 Jun 2004 23:09:04 -0700, jupiterscie...@yahoo.com (jsp)
wrote:
Saul Levy
I looked up your website. Sorry, but I never mix science and
religion! The two just don't mix.
If anyone missed the other newsgroup: No transit of Venus in the
Western US and it still occurs only on the 8th.
Saul Levy
On 6 Jun 2004 23:09:04 -0700, jupiterscie...@yahoo.com (jsp)
wrote:
>Just a reminder:
Tom Van Flandern
7:06 a.m. from Washington, DC. This is probably the most interesting
transit-related phenomenon. Some authors are calling it "mysterious",
but the explanation has been long known. See the first item under
"Current News" in the ledt column at http://metaresearch.org. -|Tom|-
Tom Van Flandern - Washington, DC - see our web site on replacement
astronomy research at http://metaresearch.org
William Hamblen
The orbit of Venus is tilted with respect to the orbit of the Earth.
To get a transit both Venus and the Earth have to be on the line where the
plane of the orbit of Venus intersects the plane of the orbit of Earth and
on the same side of the Sun. You get transits only in June or December,
starman
Because of the moon's 5-deg. inclination to the earth's orbit, the moon
is currently approaching the point of an 18-year cycle when the range of
it's declination is 5-deg. greater than the sun. The sun ranges from
+23.5 to -23.5 deg. declination during a year while the moon is getting
close to +28.5 and -28.5 deg. during each month. This will be especially
noticable near the next full moon in July, which will rise and set
farther south than the sun ever does and will follow a path across the
southern horizon lower than the sun does in December. Of course this all
applies for viewers in the northern hemisphere. The situation is
reversed for southern hemisphere observers. In about 9-years, the moon's
declination will range from +18 to -18 deg. when it's 5-deg. inclination
to the earth's orbit will subtract from the sun's declination range.
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Les &/or Claire
> Henry Spencer (or somebody else of the same name) wrote thusly in
> message <HyyCC...@spsystems.net>:
>
>> Five inferior-conjunction periods is *almost* exactly eight Earth
>> years.
>
> Fibonacci's Series rules OK :) The same period is almost exactly 13
> Venus years.
That monk has a lot to answer for.... ;o)
--
http://www.stuffmongers.com
"Homo sapiens, the first truly free species, is about to decommission
natural selection, the force that made us.... Soon we must look deep
within ourselves and decide what we wish to become." Edward O. Wilson
Consilience, The Unity of Knowledge
Remove frontal lobes to reply from a NG
Paul Schlyter
Tom Van Flandern <to...@metaresearch.org> wrote:
> Be sure to watch for the black drop effect, which occurs at about
> 7:06 a.m. from Washington, DC. This is probably the most interesting
> transit-related phenomenon. Some authors are calling it "mysterious",
> but the explanation has been long known. See the first item under
> "Current News" in the ledt column at http://metaresearch.org. -|Tom|-
Check out the images of the Venus transit here:
http://vt-2004.kva.astro.su.se/
In particular, check the iamge taken at 11:07 UT --- no black drop
visible there.
These images were taken with the 1-meter Swedish Solar Telescope at
La Palma. Canary Islands. This telescope produces the sharpest
solar images in the world.
Also check the 11:12 and 11:15 UT images carefully: there you can see
another phenomenon although faintly: the part of Venus' limb outside
the solar disk is visible, due to sunlight refracted in Venus'
atmosphere.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://www.stjarnhimlen.se/
http://home.tiscali.se/pausch/
Uwe Schürkamp
Hi Tom et al.,
thanks for the URL and your excellent write-up. Sadly I only read it
after having observed the transit in its full glory from Germany, so
I'd be more than happy if the group could confirm or deny that I
observed the black drop effect when Venus exited from the sun's disc
here:
http://www.schuerkamp.de/zope/hoover/astronomy/venus_transit_2004
The images were taken through a full aperture filtered SPC-8, using a
hand held Nikon Coolpix 950 digital camera to photograph the eyepiece
image.
The images are 1600x1200 in resolution but still quite small (less
than 80kb each) because they're mostly black and white, anyway ;-)
Cheers & thanks in advance for your comments,
uwe
PS: The common mistake you mention was re-enacted in the otherwise
great german TV science programme "quarks & co." tonight live,
mentioning atmospheric effects on Venus as the cause of the black drop
effect.
--
mail replies to Uwe at schuerkamp dot de ( yahoo address is spambox)
Uwe Schuerkamp //////////////////////////// http://www.schuerkamp.de/
Herford, Germany \\\\\\\\\\\\\\\\\\\\\\\\\\ (52.0N/8.5E)
GPG Fingerprint: 2E 13 20 22 9A 3F 63 7F 67 6F E9 B1 A8 36 A4 61
Robert Casey
>>
>>
>
>Check out the images of the Venus transit here:
>
>http://vt-2004.kva.astro.su.se/
>
>In particular, check the iamge taken at 11:07 UT --- no black drop
>visible there.
>
I don't see any teardrops either. Must be an artifact of the human eye.
I don't think
any pro astronomers ever look thru a telescope to do any real science
anymore.
And if they did, it's probably just to make sure the scope is ready to
photograph
it.
Henry Spencer
Robert Casey <wa2...@ix.netcom.com> wrote:
>>In particular, check the iamge taken at 11:07 UT --- no black drop
>>visible there.
>
>I don't see any teardrops either. Must be an artifact of the human eye.
No, it has been photographed during transits of Mercury (which also proves
that it is not a result of Venus's atmosphere).
Greg Crinklaw
> No, looks like you did your math upside down. Did you forget that the Earth
> is also spinning around the Sun so Venus actually has come catching up to
> do?
Just a friendly heads up: you might want to look up the word "spinning"
in the dictionary before you use it again...
Paul Schlyter
Henry Spencer <he...@spsystems.net> wrote:
> In article <40C660EC...@ix.netcom.com>,
> Robert Casey <wa2...@ix.netcom.com> wrote:
>
>>>In particular, check the iamge taken at 11:07 UT --- no black drop
>>>visible there.
>>
>>I don't see any teardrops either. Must be an artifact of the human eye.
>
> No, it has been photographed during transits of Mercury (which also proves
> that it is not a result of Venus's atmosphere).
The Black Drop is an effect of how our eyes perceive when two unsharp
edges between bright and dark approach one another. It can be readily
simulated by keeping two of your fingers as close to your eye as you can
and then let the fingers approach one another: they seem to touch before
they actually touch.
Ugo
news:10cdaa7...@corp.supernews.com...
Hey, thanks for the tip, but I'm perfectly aware of the meaning of the word
spinning :)
Of course "orbiting" would be the right choice of words, but I assumed we're
not dumb people here and that it would be clear from the context what I
meant...
Cheers!
Tom Randy
> In article <40C660EC...@ix.netcom.com>,
> Robert Casey <wa2...@ix.netcom.com> wrote:
>>>In particular, check the iamge taken at 11:07 UT --- no black drop
>>>visible there.
>>
>>I don't see any teardrops either. Must be an artifact of the human eye.
>
> No, it has been photographed during transits of Mercury (which also proves
> that it is not a result of Venus's atmosphere).
I saw a photo of it yesterday on someone's web site.
randyj
"Paul Schlyter" <pau...@saaf.se> wrote in message
news:ca6dua$9kf$1...@merope.saaf.se...
> The Black Drop is an effect of how our eyes perceive when two unsharp
> edges between bright and dark approach one another. It can be readily
> simulated by keeping two of your fingers as close to your eye as you can
> and then let the fingers approach one another: they seem to touch before
> they actually touch.
is that the same thing as seeing the drop effect in front of the sun?
somebody else explained on here, i think it was at metaresearch.org
or something, that it is due to moving cells of air in the atmosphere.
rj
Dave
I haven't read that particular explanation, but if you check what else is on
the site, it's probably a load of *****.
DaveL
Pat O'Connell
As did I. Not everyone captured the effect, but it can be captured on
film. SWAG: an atmospheric effect?
--
Pat O'Connell
[note munged EMail address]
Take nothing but pictures, Leave nothing but footprints,
Kill nothing but vandals...
Paul Schlyter
Well, these moving cells do increase the fuzziness of the limbs of the
Sun and of Venus...
James Whitby
> As did I. Not everyone captured the effect, but it can be captured on
> film. SWAG: an atmospheric effect?
I saw a lecture that stated that the effect was due to blurring caused
by a combination of diffraction effects and terrestrial atmospheric
turbulence, these are apparently exarcebated in small aperture
telescopes. A demonstration showed a white circle on a black background
approaching a white edge for different spacings (5..1 pixels)and
different applications of gaussian blur (using Photoshop or similar).
This produced an effect very like images of the black-drop effect.
--
J Whitby
James Whitby
>
>> As did I. Not everyone captured the effect, but it can be captured on
>> film. SWAG: an atmospheric effect?
>
>
>
> I saw a lecture that stated that the effect was due to blurring caused
> by a combination of diffraction effects and terrestrial atmospheric
> turbulence,
For a more detailed explanation see Icarus 168 pp249-256 (2004),
abstract available from ADS:
--
Dr. James Whitby Tel: +41 (0)31 6314409
Physikalisches Institut Fax: +41 (0)31 6314405
Universitaet Bern
Sidlerstrasse 5
3012 Bern, Switzerland.
Tom Van Flandern
> [US]: I'd be more than happy if the group could confirm or deny that I
observed the black drop effect when Venus exited from the sun's disc
here...
As you can see from this processed version of your photo, you nailed
it:
http://metaresearch.org/home/viewpoint/black_drop-sm.jpg
Very nice work. The black drop is an elusive feature, but yours is
one of the best photos I have seen. With your permission, I'd like to
include this in my article, attributed to you and including your email
address (as above). If others deserve credit too or you have some
preference for the citation, just let me know. And thanks for sharing
your fine results! -|Tom|-
Tom Van Flandern
> The Black Drop is an effect of how our eyes perceive when two unsharp
> edges between bright and dark approach one another. It can be readily
> simulated by keeping two of your fingers as close to your eye as you
can
> and then let the fingers approach one another: they seem to touch
before
> they actually touch.
They gave this example on NASA TV also, but it is a bit misleading
because the fingers effect is caused by diffraction (wave bending as a
sharp edge intervenes), whereas the black drop effect is caused by
variable refraction from moving air cells in Earth's atmosphere. Light
in space is not spread in this way, as is evident from photoelectric
observations of lunar occultations, which show the star disappearing in
milliseconds rather than seconds. (That effect really is caused by
diffraction.) -|Tom|-
Uwe Schürkamp
> "Uwe Schürkamp" <hoo...@hoover.dyndns.org> writes:
>
>> [US]: I'd be more than happy if the group could confirm or deny that I
> observed the black drop effect when Venus exited from the sun's disc
> here...
>
> As you can see from this processed version of your photo, you nailed
> it:
> http://metaresearch.org/home/viewpoint/black_drop-sm.jpg
>
> Very nice work. The black drop is an elusive feature, but yours is
> one of the best photos I have seen. With your permission, I'd like to
> include this in my article, attributed to you and including your email
> address (as above). If others deserve credit too or you have some
> preference for the citation, just let me know. And thanks for sharing
> your fine results! -|Tom|-
<blush> Thanks much for the kind words, I'd be more than happy if you
have additional use for the images. I can also provide you with the
"original" image should you need it.
Thanks in turn for your nice article on metaresearch.org, Tom!
All the best,
uwe
Chris Thompson
Mauritz Geyser <maur...@iafrica.com> wrote:
>Alexander! You saw the Transit of Venus the last time?? You must be very
>very old!!
The BBC kept talking about it being an event "that no living person has seen".
I rather hoped that a one-hundred-and-thirty-mumble-old Georgian would turn
up and contradict this...
Chris Thompson
Email: cet1 [at] cam.ac.uk
Greg Hennessy
> somebody else explained on here, i think it was at metaresearch.org
> or something, that it is due to moving cells of air in the atmosphere.
I'm not sure what it says at metaresearch.org, but since the black
drop effect was seen when Mercury transited the sun as observed by a
spacecraft, the black drop effect cannot be due to either the earths
atmosphere or the atmosphere of the planet in transit.
Greg Hennessy
> because the fingers effect is caused by diffraction (wave bending as a
> sharp edge intervenes), whereas the black drop effect is caused by
> variable refraction from moving air cells in Earth's atmosphere.
The black drop effect cannot be from an atmospheric effect, Pasachof
has observed the effect on the planet Mercury from the TRACE
spacecraft.
David Nakamoto
brightness (or in this case darkness) bleeding towards or into one another.
A trick of perception. What I find curious is, at least to my knowledge,
the assertion that this effect was caused by the atmosphere of either Venus
or Earth was still in print fairly recently, despite the counter evidence of
Mercury transits at least for the Venus atmosphere case.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
A man is a god in ruins.
--- Duke Ellington
----------------------------------------------------------------------
"Greg Hennessy" <greg.h...@tantalus.cox.net> wrote in message
news:ca858n$kir$1...@tantalus.no-ip.org...
Tom Van Flandern
> I'm not sure what it says at metaresearch.org, but since the black
drop effect was seen when Mercury transited the sun as observed by a
spacecraft, the black drop effect cannot be due to either the earth's
atmosphere or the atmosphere of the planet in transit.
I saw my first transit of Mercury and first black drop
effect in 1960. It has always been obvious that the atmosphere of the
transiting planet has nothing to do with the black drop effect because
Mercury has no atmosphere.
But think about what you are saying. Earth does have an
atmosphere, and the light from the transit must pass through it. Our
atmosphere slightly distorts all light passing through it. Why should
transits be an exception?
Lunar occultations prove that the apparent enlargement of
the Sun's and Moon's disks caused by irradiation does not occur in
space. So it must happen in Earth's atmosphere. And stellar "seeing"
disks show that it does happen here, caused by variable refraction in
moving air cells.
At the Meta Research site you will find the evidence and
details. See
http://metaresearch.org/home/viewpoint/blackdrop.asp.
Be sure not to be one of those people who can't unlearn things once
learned wrongly. Look at the evidence and draw your own conclusions
anew, without the influence of the bias of having previously held a
contrary position. -|Tom|-
randyj
"Tom Van Flandern" <to...@starpower.net> wrote in message
news:40c897e0$0$2991$61fe...@news.rcn.com...
> "Greg Hennessy" <greg.h...@tantalus.cox.net> writes:
>
> > I'm not sure what it says at metaresearch.org, but since the black
> drop effect was seen when Mercury transited the sun as observed by a
> spacecraft, the black drop effect cannot be due to either the earth's
> atmosphere or the atmosphere of the planet in transit.
>
> I saw my first transit of Mercury and first black drop
> effect in 1960. It has always been obvious that the atmosphere of the
> transiting planet has nothing to do with the black drop effect because
> Mercury has no atmosphere.
>
> But think about what you are saying. Earth does have an
> atmosphere, and the light from the transit must pass through it. Our
> atmosphere slightly distorts all light passing through it. Why should
> transits be an exception?
>
> Lunar occultations prove that the apparent enlargement of
> the Sun's and Moon's disks caused by irradiation does not occur in
> space. So it must happen in Earth's atmosphere. And stellar "seeing"
> disks show that it does happen here, caused by variable refraction in
> moving air cells.
>
someone mentioned? It too saw the black drop effect in a Mercury
transit from outside
the atmosphere, according to whoever posted that.
rj
Greg Hennessy
> atmosphere, and the light from the transit must pass through it. Our
> atmosphere slightly distorts all light passing through it. Why should
> transits be an exception?
You are proposing a logical fallacy.
Earth's atmosphere distorts light.
The black drop effect is a light distortion.
The earth's atmosphere causes the black drop effect.
The logical fallacy is because other effects besides the earths
atmosphere distort light.
If the black drop effect is from the earths atmosphere, how come the
TRACE sattelite saw the effect?
Jonathan Silverlight
<greg.h...@tantalus.cox.net> writes
Do you have a reference to an observation of Mercury from a spacecraft
(and did TRACE "see" a black drop on Venus ?) I know the Mercury
observation from the ground rules out the other planet's atmosphere as a
cause.
--
Remove spam and invalid from address to reply.
Greg Hennessy
Jonathan Silverlight <jsilve...@spam.merseia.fsnet.co.uk.invalid> wrote:
> Do you have a reference to an observation of Mercury from a spacecraft
> (and did TRACE "see" a black drop on Venus ?)
Yes, http://nicmosis.as.arizona.edu:8000/POSTERS/TOM1999.jpg. I do not
know if TRACE saw a black drop effect with Venus.
tho...@antispam.ham
> Greg Hennessy writes:
>> I'm not sure what it says at metaresearch.org, but since the black
>> drop effect was seen when Mercury transited the sun as observed by a
>> spacecraft, the black drop effect cannot be due to either the earth's
>> atmosphere or the atmosphere of the planet in transit.
> I saw my first transit of Mercury and first black drop
> effect in 1960. It has always been obvious that the atmosphere of the
> transiting planet has nothing to do with the black drop effect because
> Mercury has no atmosphere.
>
> But think about what you are saying. Earth does have an
> atmosphere, and the light from the transit must pass through it. Our
> atmosphere slightly distorts all light passing through it. Why should
> transits be an exception?
Why don't you practice what you preach and think about what you are
saying. Greg said the effect was observed by a spacecraft, therefore
your entire reference to the Earth's atmosphere is irrelevant.
Benign Vanilla
"Jonathan Silverlight" <jsilve...@spam.merseia.fsnet.co.uk.invali> wrote
in message news:VtbloJCQ...@merseia.fsnet.co.uk...
<snip>
> Do you have a reference to an observation of Mercury from a spacecraft
> (and did TRACE "see" a black drop on Venus ?) I know the Mercury
> observation from the ground rules out the other planet's atmosphere as a
> cause.
Third picture down on
http://solar.physics.montana.edu/handy/trace/mercury/
BV.
Jonathan Silverlight
<BVre...@tibetanbeefgarden.com> writes
Thanks, and thanks to Greg, too. Isn't the 1600A picture dramatic,
though?
Over to you, Tom.
Tom Van Flandern
"Greg Hennessy" <greg.h...@tantalus.cox.net> writes:
>> [tvf]: Earth does have an atmosphere, and the light from the transit
must pass through it. Our atmosphere slightly distorts all light passing
through it. Why should transits be an exception?
> [Hennessy]: You are proposing a logical fallacy.
-- Earth's atmosphere distorts light.
-- The black drop effect is a light distortion.
-- The earth's atmosphere causes the black drop effect.
The logical fallacy is because other effects besides the earths
atmosphere distort light.
Earth's atmosphere produces an effect on starlight,
moonlight, and sunlight entering it that enlarges those visible disks.
The known effect produced by Earth's atmosphere is
qualitatively necessary and quantitatively sufficient to produce the
observed black drop effect.
Therefore, no other causes are needed in the case of
transits.
> [Hennessy]: If the black drop effect is from the earths atmosphere,
how come the TRACE satellite saw the effect?
Thanks very much for mentioning the article you cited at
http://nicmosis.as.arizona.edu:8000/POSTERS/TOM1999.jpg, which I will
add to the bibliography for my article with an acknowledgement to you.
It is about space-based observations of transits of Mercury that
reported seeing the black drop effect. However, what the article says is
consistent with my own article and many others before it. The
investigators agree that the image spreading (their "point-spread
function" of PSF) is essential to the black drop effect, and that the
primary cause of the black drop for ground-based observers is
atmospheric "seeing" because that is the main cause of image spreading
(PSF) on the ground. Their point was that diffraction is also present
and, although much smaller than "seeing" effects, becomes the dominant
cause of image spreading (PSF) in space where there is no atmospheric
effect. (I had already mentioned diffraction as a secondary cause in my
section on image spreading for lunar occultations.) Therefore, a small
black drop effect is still seen by spacecraft unless one corrects for
limb darkening, in which case the black drop effect can be effectively
removed from the data.
Here are three paragraphs with the actual words of these authors:
[from abstract]: ". we examined the images in and around the point of
internal tangency for evidence of the historical 'Black Drop' effect.
After calibration (including careful removal of image/instrumental
artifacts and flat-fielding) the only radially directed brightness
anisotropies found were due to the interacting effects of diffracted
limb-darkened photospheric light around the Mercurian disk and the
instrument's Point Spread Function (PSF). We discuss, and model, these
effects as they would have applied to earlier ground-based observations
of Mercurian transits (also including the effects of atmospheric
"seeing") to explain the historical basis for the Black Drop effect."
[from text]: "Shortly after the 1769 transit of Venus [I], De la Lande
identified the origin of this effect in blurring due to atmospheric
turbidity (i.e., 'seeing'). Today, space-based transit observations are,
of course, devoid of, (time variable) atmospheric seeing effects,
previously modeled [3]. Nonetheless, the Black Drop effect arises due to
the finite instrumental resolution (blurring by the instrumental PSF)
convolved with the solar limb-darkening profile."
[from conclusion]: "The principal cause of the Black Drop effect, which
has historically impeded ground-based planetary transit measurements, is
optical broadening due to the convolution of the systemic PSF with the
planetary and limb-darkened solar disks. TRACE [satellite] observations
are free from PSF instabilities due to 'seeing' in the terrestrial
atmosphere and allow mitigation of the Black Drop effect from the
intrinsic disk images."
"Mitigation" means "lessening". The ground-based black drop
effect caused by "seeing" is not present in space, but a lesser effect
from a different cause (diffraction) is still present there. Unlike
rapidly time-variable "seeing" effects, diffraction and limb-darkening
effects can be easily modeled and corrected for. The ground observers
have no such luxury.
and <tho...@antispam.ham> writes:
> [Tholen]: Why don't you practice what you preach and think about what
you are saying. Greg said the effect was observed by a spacecraft,
therefore your entire reference to the Earth's atmosphere is irrelevant.
Tholen, you are a professional, and are supposed to be
helping matters, not spreading disinformation. In this case, I'm taking
about information that has been known for over 200 years, not some
theory of mine. See for example the references in Peter Abraham's first
message in the current thread "black drop, longer explanation" in
newsgroup <sci.astro.amateur>.
You could have read my article, the other references, or the
spacecraft article, and set matters straight yourself, even if you have
never personally seen the black drop effect. Instead, you opted for the
chance to take another shot at me, rather than helping to get the
science right. Pathetic. When will you get that this isn't about you or
me, but about advancing science? -|Tom|-
tho...@antispam.ham
>> Why don't you practice what you preach and think about what
>> you are saying. Greg said the effect was observed by a spacecraft,
>> therefore your entire reference to the Earth's atmosphere is irrelevant.
> Tholen, you are a professional, and are supposed to be
> helping matters, not spreading disinformation.
I did help matters by noting that the effect was observed by a spacecraft,
therefore your entire reference to the Earth's atmosphere is irrelevant.
> In this case, I'm taking
> about information that has been known for over 200 years, not some
> theory of mine.
You're talking about some explanation that involves the Earth's
atmosphere, which cannot explain the effect seen by a spacecraft.
> See for example the references in Peter Abraham's first
> message in the current thread "black drop, longer explanation" in
> newsgroup <sci.astro.amateur>.
Unnecessary. In a nutshell, we have the following:
Q: What causes the black drop effect?
A: The Earth's atmosphere.
Q: But a spacecraft observed the black drop effect, so doesn't
that invalidate the claim that it's caused by the Earth's
atmosphere?
A: Think about what you are saying. Earth does have an atmosphere,
and the light from the transit MUST [emphasis added] pass
through it.
Sorry, but from the spacecraft's perspective, the light does not
have to pass through the Earth's atmosphere, which means that you
didn't think about what you said.
> You could have read my article, the other references, or the
> spacecraft article, and set matters straight yourself,
The matter had already been set straight. I was merely recommending
that you practice what you preach and think about what you are saying.
> even if you have
> never personally seen the black drop effect. Instead, you opted for the
> chance to take another shot at me,
That's rather ironic, coming from someone who has taken shots at me.
> rather than helping to get the science right.
That's rather ironic, coming from someone saying that the light from
the transit must pass through the Earth's atmosphere, even for a
spacecraft.
> Pathetic.
My sentiments exactly.
> When will you get that this isn't about you or
> me, but about advancing science? -|Tom|-
The science had already been advanced, Tom. It's about you telling
someone to think about what they're saying while not doing so yourself.
Greg Crinklaw
> The science had already been advanced, Tom. It's about you telling
> someone to think about what they're saying while not doing so yourself.
I'm not a big fan of Tom's (I think he's a borderline nut and I sure
wish he'd ask more informed questions at the MER briefings), but I must
say your response to him is both childish and personal. In the end it
is *you* who aren't paying enough attention to what is being said before
commenting (or thinking). Tom explained clearly enough how this affect
has the same basic cause with or without the atmosphere, only that the
atmosphere exacerbates it. I think you should ask yourself one simple
question: do you have anything to offer regarding this phenomenon other
than ridicule?
tho...@antispam.ham
>> The science had already been advanced, Tom. It's about you telling
>> someone to think about what they're saying while not doing so yourself.
> I'm not a big fan of Tom's (I think he's a borderline nut and I sure
> wish he'd ask more informed questions at the MER briefings), but I must
> say your response to him is both childish and personal.
No more childish and personal than Tom's response to Greg Hennessy. I
have often found that the best educational tool is to use that which
the person being educated uses himself.
> In the end it
> is *you* who aren't paying enough attention to what is being said before
> commenting (or thinking).
Incorrect, Greg, and ironically, you have demonstrated that you haven't
paid enough attention to what was said before commenting. See below.
> Tom explained clearly enough how this affect
> has the same basic cause with or without the atmosphere, only that the
> atmosphere exacerbates it.
I suggest you go back and read Tom's original reply to Greg Hennessy
(reproduced below for your convenience). Nowhere did he say that the
atmosphere exacerbates it. Indeed, he stated quite unambiguously
that the effect "must happen in the Earth's atmosphere". It was only
*after* Greg Hennessy and I called attention to his failure to think
about what he was saying that he changed his explanation.
> I think you should ask yourself one simple
> question: do you have anything to offer regarding this phenomenon other
> than ridicule?
I am offering the facts on the sequence of statements that have
occurred during the course of this discussion. Here is the
relevant portion of Tom's original response to Greg Hennessy:
] But think about what you are saying. Earth does have an
] atmosphere, and the light from the transit must pass through it. Our
] atmosphere slightly distorts all light passing through it. Why should
] transits be an exception?
]
] Lunar occultations prove that the apparent enlargement of
Greg Hennessy
Tom Van Flandern <to...@metaresearch.org> wrote:
> The known effect produced by Earth's atmosphere is
> qualitatively necessary and quantitatively sufficient to produce the
> observed black drop effect.
False. The earth's atmosphere CANNOT be necessary to produce the black
drop effect, since the effect is seen from TRACE.
If you want to argue that the earth's atmosphere INCREASES the black
drop effect, you can, but you cannot aruge it CAUSES it.
Greg Crinklaw
>>Tom explained clearly enough how this affect
>>has the same basic cause with or without the atmosphere, only that the
>>atmosphere exacerbates it.
>
> I suggest you go back and read Tom's original reply to Greg Hennessy
> (reproduced below for your convenience). Nowhere did he say that the
> atmosphere exacerbates it. Indeed, he stated quite unambiguously
> that the effect "must happen in the Earth's atmosphere". It was only
> *after* Greg Hennessy and I called attention to his failure to think
> about what he was saying that he changed his explanation.
Actually, had you taking the time to read his elaboration it should be
obvious that he simply didn't make himself very clear in his first post.
I don't understand why you are intentionally ignoring his
clarification, preferring to attack him based on your erroneous
interpretation of his poorly worded original statement. That, sir, is
not the sign of someone being rational...
> I am offering the facts on the sequence of statements that have
> occurred during the course of this discussion. Here is the
> relevant portion of Tom's original response to Greg Hennessy:
Are you a lawyer by trade? You seem intent on using his words against
him even after he later clarified what he meant. I'll ask one more
time: do you have anything relevant to offer regarding the topic at
hand? Because I've got to say I find Tom's remarks and links far more
insightful than your continued childish personal attacks against him and
I doubt I'm the only one...
If you two have some sort of personal feud, then please consider that
the rest of us don't give a damn!
tho...@antispam.ham
>>> Tom explained clearly enough how this affect
>>> has the same basic cause with or without the atmosphere, only that the
>>> atmosphere exacerbates it.
>> I suggest you go back and read Tom's original reply to Greg Hennessy
>> (reproduced below for your convenience). Nowhere did he say that the
>> atmosphere exacerbates it. Indeed, he stated quite unambiguously
>> that the effect "must happen in the Earth's atmosphere". It was only
>> *after* Greg Hennessy and I called attention to his failure to think
>> about what he was saying that he changed his explanation.
> Actually, had you taking the time to read his elaboration it should be
> obvious that he simply didn't make himself very clear in his first post.
On the contrary, he did make himself very clear in his first post on
the subject, which was:
] Be sure to watch for the black drop effect, which occurs at about
] 7:06 a.m. from Washington, DC. This is probably the most interesting
] transit-related phenomenon. Some authors are calling it "mysterious",
] but the explanation has been long known. See the first item under
] "Current News" in the ledt column at http://metaresearch.org. -|Tom|-
> I don't understand why you are intentionally ignoring his
> clarification,
Tom's so-called "clarification" came *after* I noted that he didn't
practice what he preached, therefore I could not have ignored that
which had not yet happened, Greg.
> preferring to attack him based on your erroneous
> interpretation of his poorly worded original statement.
You're erroneously presupposing that my interpretation of his original
statement is erroneous, Greg.
> That, sir, is not the sign of someone being rational...
And your erroneous presupposition is the sign of what, Greg,
rationality?
>> I am offering the facts on the sequence of statements that have
>> occurred during the course of this discussion. Here is the
>> relevant portion of Tom's original response to Greg Hennessy:
> Are you a lawyer by trade?
Irrelevant; you asked whether I had anything to offer other than
ridicule, and I responded that I am offering the facts.
> You seem intent on using his words against
> him even after he later clarified what he meant.
He never clarified his statement to "think about what you are saying",
Greg. He simply didn't follow his own advice. That he needed to
clarify another statement of his demonstrates that he didn't follow
his own advice.
> I'll ask one more
> time: do you have anything relevant to offer regarding the topic at
> hand?
Why are you repeating a question that has already been answered, Greg?
> Because I've got to say I find Tom's remarks and links far more
> insightful
How do you find Tom's remarks and links on the artificial structures
on Mars, Greg? Insightful?
http://www.metaresearch.org/solar%20system/cydonia/asom/pressconf_nyc.asp
> than your continued childish personal attacks against him and
> I doubt I'm the only one...
On what basis do you call it a childish personal attack, Greg? Tom
told Greg Hennessy to think about what he was saying, and I told
Tom to practice what he preaches. If you find that to be a childish
personal attack, then why haven't you taken Tom to task for his
childish personal attack on Greg Hennessy?
> If you two have some sort of personal feud, then please consider that
> the rest of us don't give a damn!
You obviously do, Greg; witness your responses.
Greg Crinklaw
Earns the *PLONK* from me for being hard headed and unreasonable with
ntohing to offer except vapid personal arguments.
Congratulations.
tho...@antispam.ham
> Earns the *PLONK* from me for being hard headed and unreasonable with
> ntohing to offer except vapid personal arguments.
Ironically, you have nothing to offer except unwarranted allegations of
"vapid personal argunments".
Larry Burford
The TRACE photos are very interesing. There is some obvious additional
darkening in the subject area over and above limb darkening.
If I had seen these pictures before seeing pictures of the real black
drop effect, I'd have thought "cool, the black drop effect".
But I have seen black drop effect photos taken from the ground. IMO,
we need a new name, something like the "grey drop effect", for what
TRACE recorded.
LB
Tom Van Flandern
>> [tvf]: The known effect produced by Earth's atmosphere is
qualitatively necessary and quantitatively sufficient to produce the
observed black drop effect.
> [Hennessy]: False. The earth's atmosphere CANNOT be necessary to
produce the black drop effect, since the effect is seen from TRACE. If
you want to argue that the earth's atmosphere INCREASES the black drop
effect, you can, but you cannot argue it CAUSES it.
Okay, if it helps you sleep better at nights knowing that
you were RIGHT and I was WRONG and to use capital letters to make that
point, be my guest.
But as my article made clear to most readers, the
atmospheric black drop is caused by variable refraction, and the space
black drop is caused by diffraction. These are two different physical
mechanisms, one of which exists in atmospheres and the other does not.
However, I agree they have in common that they spread light, and in that
technical sense, Earth's atmosphere only increases the effect. Of
course, it increases the effect by overwhelming and hiding the
diffraction mechanism while making the effect time variable, not by
amplifying diffraction.
Are we on the same page now?
BTW, were you offended by my phrase in an earlier message,
where I said "but think about what you are saying", as Dave Tholen
claims? If so, you have my apology. I certainly meant no offense. Your
comments have been on topic and have generally advanced the discussion,
even if the above point does strike me as a bit pedantic. -|Tom|-
Greg Hennessy
> you were RIGHT and I was WRONG and to use capital letters to make that
> point, be my guest.
It helps me sleep at night to make sure correct information is being
propagated.
> But as my article made clear to most readers, the
> atmospheric black drop is caused by variable refraction, and the space
> black drop is caused by diffraction. These are two different physical
> mechanisms, one of which exists in atmospheres and the other does not.
You are now claiming that there exist *TWO* black drop effects, which
I don't think is correct. There is one black drop effect, and the
black drop effect can be made worse by variable refraction from an
atmosphere.
> However, I agree they have in common that they spread light, and in that
> technical sense, Earth's atmosphere only increases the effect.
I am glad that you agree there is one effect, I don't know why you
have to add "in a technical sense".
> Of
> course, it increases the effect by overwhelming and hiding the
> diffraction mechanism while making the effect time variable, not by
> amplifying diffraction.
>
> Are we on the same page now?
I don't agree with the phrasing that it overwhelms and hides the
diffraction mechanism.
> BTW, were you offended by my phrase in an earlier message,
> where I said "but think about what you are saying", as Dave Tholen
> claims?
I wasn't offended by it, but I thought you were proposing an incorrect
explanation for the black drop effect while chastising me for not
thinking. Which is rather, umm, unpolitic?
> Your
> comments have been on topic and have generally advanced the discussion,
> even if the above point does strike me as a bit pedantic.
I'm an astrometrist working for the US Naval Observatory. I am
*supposed* to be pedantic. I'm sure you can agree. :)
tho...@antispam.ham
> BTW, were you offended by my phrase in an earlier message,
> where I said "but think about what you are saying", as Dave Tholen
> claims?
I made no claim that anyone was offended by your phrase, Tom. I
merely noted that you didn't practice what you preached.
Steve Willner
should know better. Let's see if we can clear things up.
First of all, does anyone claim the poster Greg Hennessy pointed out
http://nicmosis.as.arizona.edu:8000/POSTERS/TOM1999.jpg
is wrong? (Thanks, Greg.) To me it looks clear and straightforward,
and I don't see any obvious mistakes, but as I say, I'm no expert.
In article <40ca2f0a$0$3042$61fe...@news.rcn.com>,
"Tom Van Flandern" <to...@starpower.net> writes:
> The
> investigators agree that the image spreading (their "point-spread
> function" of PSF) is essential to the black drop effect,
That's how I read the poster. The other ingredient is the extreme
limb darkening near the edge of the Solar disk.
> and that the
> primary cause of the black drop for ground-based observers is
> atmospheric "seeing" because that is the main cause of image spreading
> (PSF) on the ground.
I don't see where the poster said this explicitly, but it was the
clear implication and certainly looks correct to me.
> Their point was that diffraction is also present
> and, although much smaller than "seeing" effects, becomes the dominant
> cause of image spreading (PSF) in space where there is no atmospheric
> effect.
This, on the other hand, is not what the poster said. The dominant
effect in the TRACE observations was the PSF of the TRACE optics,
presumably a combination of diffraction in the TRACE camera, optical
aberrations, and the detector pixel size.
The diffraction mentioned in the poster is Fresnel diffraction at the
limb of Mercury. It was found to be a small but not zero effect in
the TRACE observations and would be negligible in typical ground-
based observations.
The bottom line is that a black drop effect should be seen in any
solar transit, and the magnitude of the effect should depend on the
PSF of the observation. For typical observations from Earth's
surface, the atmosphere will be a factor in determining the PSF.
> (I had already mentioned diffraction as a secondary cause in my
> section on image spreading for lunar occultations.)
Fresnel diffraction is a huge effect for lunar occultations. I
_think_ the reason it is so important is that the stars being
occulted are so much smaller in angular size than Mercury's disk, but
I may be mistaken. The wavelength of observation is also a factor;
I'm most familiar with observations in the infrared, where
diffraction is more important. Figure 1 of Ridgway, Wells, & Joyce
(1977 AJ 82, 414) is a fine illustration of Fresnel diffraction in a
lunar occultation. (There are probably even better illustrations
around, but this was the first one I happened across in a quick ADS
search.)
--
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)
Steve Willner
wil...@cfa.harvard.edu (Steve Willner) writes:
> The bottom line is that a black drop effect should be seen in any
> solar transit, and the magnitude of the effect should depend on the
> PSF of the observation.
It occurred to me later that this shouldn't be hard to model. It
might make a fun little project for someone. I wouldn't be surprised
if it has already been done in the literature, but that shouldn't
stop anyone who wants to play with the idea.
You might start by modelling the Sun's disk with a surface brightness
that goes as cos(pi/2*r/R), where R is the solar radius (about 15
arcmin) and r is the projected distance from the center of the Sun.
Anybody want to suggest a more accurate formula? I would suggest a
grid of 0.01 arcsec pixels. That would be a pretty big grid for the
whole Sun, but you only have to model a small area near the limb.
Choose a distance between the center of Mercury and the Sun's limb,
and set all the pixels that Mercury covers to zero. Mercury has a
diameter of about 11 arcsec, so that's a circle of diameter about
1100 pixels. (You might want to check my numbers!) Now you have an
image of what a transit would look like if observed with near-perfect
optics and seeing.
To model the optics and seeing, convolve your "perfect" image with
Gaussians of various diameters. Or you could try other functional
forms such as Airy disks. I'd suggest using 0.1 arcsec pixels at
this stage, but you might want to use larger ones. Convert your
"observed" images into a form that can be displayed (gif or tiff or
fits, perhaps), and see what parameters lead to a black drop.
If anyone tries this, please let us know your results.
Ernie Wright
> To model the optics and seeing, convolve your "perfect" image with
> Gaussians of various diameters. Or you could try other functional
> forms such as Airy disks. I'd suggest using 0.1 arcsec pixels at
> this stage, but you might want to use larger ones. Convert your
> "observed" images into a form that can be displayed (gif or tiff or
> fits, perhaps), and see what parameters lead to a black drop.
>
> If anyone tries this, please let us know your results.
It's even easier than this sounds. As a first pass, it isn't necessary
to model limb darkening or worry about image scale. Just draw a circle
in Photoshop and try a few different radii for the Gaussian blur filter.
See
http://home.comcast.net/~erniew/astro/bd.html
In addition to the PSF, there appear to be sensor properties that can
contribute to the effect. Simulating non-linear response and limited
dynamic range enhanced the effect substantially.
- Ernie http://home.comcast.net/~erniew
Brian Tung
> It's even easier than this sounds. As a first pass, it isn't necessary
> to model limb darkening or worry about image scale. Just draw a circle
> in Photoshop and try a few different radii for the Gaussian blur filter.
> See
>
> http://home.comcast.net/~erniew/astro/bd.html
>
> In addition to the PSF, there appear to be sensor properties that can
> contribute to the effect. Simulating non-linear response and limited
> dynamic range enhanced the effect substantially.
I tried it myself. The black drop effect even when the dark disc is quite
a ways away from third contact is startling.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
Ernie Wright
> I tried it myself. The black drop effect even when the dark disc is
> quite a ways away from third contact is startling.
I made an animation this morning that shows this pretty well. I've
added it to
http://home.comcast.net/~erniew/astro/bd.html
along with some changes and corrections to the text.
- Ernie http://home.comcast.net/~erniew
Stuart Levy
>In article <40ce1698$1...@cfanews.cfa.harvard.edu>,
> wil...@cfa.harvard.edu (Steve Willner) writes:
>> The bottom line is that a black drop effect should be seen in any
>> solar transit, and the magnitude of the effect should depend on the
>> PSF of the observation.
>
>It occurred to me later that this shouldn't be hard to model. It
>might make a fun little project for someone. I wouldn't be surprised
>if it has already been done in the literature, but that shouldn't
>stop anyone who wants to play with the idea.
Sure enough it has been done -- I stumbled across this
30-year-old paper on the morning of the transit, after someone
had asked how the Earth's atmosphere related to the black-drop
effect and I'd struggled to find a credible answer.
Unfortunately my stupid newsreader won't let me post >80-char lines
so you'll have to paste these two together with no space
after the question mark:
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?
bibcode=1974A%26A....31..239W&db_key=AST
Its author simulates the black drop effect using atmospheric blurring
and solar limb-darkening, and includes illustrations which include
believable-looking black drops -- pretty much as you suggest below
though with a better limb-darkening model. Pretty cool. It makes a
lot more sense now.
Stuart Levy
Odysseus
>
> Unfortunately my stupid newsreader won't let me post >80-char lines
> so you'll have to paste these two together with no space
> after the question mark:
>
> http://adsabs.harvard.edu/cgi-bin/nph-bib_query?
> bibcode=1974A%26A....31..239W&db_key=AST
>
--
Odysseus