Parallax by Day
Anthony Ayiomamitis
Pete Lawrence and I pooled our work from yesterday surrounding the
near-occultation of Regulus by the moon to produce an interesting view
of how Regulus appeared relatively to the moon for the two of us
separated by 2370 km apart.
For an interesting comparison of this apparent view, please see
http://www.perseus.gr/Astro-Lunar-Parallax.htm .... someone please
provide oriel with his medication before he starts mumbling het again
about astrologers, axial rotation, apparent frames of reference and
whatever else I may have missed.
Clear skies!
Anthony.
Jim
I'm not sure he actually _understands_ apparent frames of reference. If
he did then he might actually shut up for a while.
Very nice work both of you, by the way :-)
Jim
--
Find me at http://www.ursaMinorBeta.co.uk
My lucky star is probably Eta Carinae.
Ben
wrote:
> Dear group,
>
> Pete Lawrence and I pooled our work from yesterday surrounding the
> near-occultation of Regulus by the moon to produce an interesting view
> of how Regulus appeared relatively to the moon for the two of us
> separated by 2370 km apart.
>
> provide oriel with his medication before he starts mumbling het again
> about astrologers, axial rotation, apparent frames of reference and
> whatever else I may have missed.
>
> Clear skies!
>
> Anthony.
Cool, gentlemen. Exponentially cool.
Praises to the both of you.
Thorazine ( iv drip ) for the crazy guy.
Ben
Richard Tobin
Anthony Ayiomamitis <ant...@perseus.no2spam.gr> wrote:
>For an interesting comparison of this apparent view, please see
>http://www.perseus.gr/Astro-Lunar-Parallax.htm
Very nice.
I think the inverse picture would also be interesting, with one image
of Regulus and two of the moon. Would the difference in fullness of
the moon be visible?
-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
Anthony Ayiomamitis
> In article <f34cha$ehj$1...@mouse.otenet.gr>,
> Anthony Ayiomamitis <ant...@perseus.no2spam.gr> wrote:
>
>
>>For an interesting comparison of this apparent view, please see
>>http://www.perseus.gr/Astro-Lunar-Parallax.htm
>
>
> Very nice.
Glad you like it.
>
> I think the inverse picture would also be interesting, with one image
> of Regulus and two of the moon. Would the difference in fullness of
> the moon be visible?
I thought about this as well ... it can be done and it would probably be
best to have the current moon as is and simply add the second (higher)
moon using Pete's Regulus as reference and with a thin artificial
separator between the two moons.
Anthony.
>
> -- Richard
G.T.
Hear hear! Very cool.
Greg
--
The ticketbastard Tax Tracker:
http://www.ticketmastersucks.org/tracker.html
Dethink to survive - Mclusky
oriel36
wrote:
> Dear group,
>
> Pete Lawrence and I pooled our work from yesterday surrounding the
> near-occultation of Regulus by the moon to produce an interesting view
> of how Regulus appeared relatively to the moon for the two of us
> separated by 2370 km apart.
>
> provide oriel with his medication before he starts mumbling het again
> about astrologers, axial rotation, apparent frames of reference and
> whatever else I may have missed.
>
> Clear skies!
>
> Anthony.
.
The Roemerian insight on the astronomical adjustment know as the
Equation of Light is based on orbital comparisons just as Kepler's
refinement of orbital geometries is based on orbital comparisons.
http://books.google.com/books?id=N6T-N2p7Qf8C&pg=PA227&dq=roemer+jupiter+earth
There is nothing remotely difficult in determining that the illusion
of the irregular motion of Io is due to finite light speed and this is
how the great astronomers understood it .Because the Flamsteed/Newton
maneuver of introducing the astrological framework into heliocentric
reasoning,Bradley finished heliocentricity off by invoking the
background stars and paralax to account for the Roiemerian insight.
The irregular motion of Io still can be seen today and the insight of
Roemer can still be appreciated without appealing to stellar
parallax but rather to orbital comparisons between a moving Earth and
slower orbitally moving Jupiter -
http://homepage.ntlworld.com/heather.hobden1/JupiterIo.jpg
http://www.msgc.org/images/ioshadow_msgc.gif
A real astronomer would be taking note of the change in the
orientation of Io's shadow due to the change in orbital positions
between Earth and Jupiter as both planets orbit the central star.
Go back to occultations,personally I think birdwatching photography is
far more difficult than what you do.At least the birdwatchers put
thing in correct context.
Anthony Ayiomamitis
> On May 24, 4:54 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
> wrote:
>
>>Dear group,
>>
>>Pete Lawrence and I pooled our work from yesterday surrounding the
>>near-occultation of Regulus by the moon to produce an interesting view
>>of how Regulus appeared relatively to the moon for the two of us
>>separated by 2370 km apart.
>>
>>For an interesting comparison of this apparent view, please seehttp://www.perseus.gr/Astro-Lunar-Parallax.htm.... someone please
>>provide oriel with his medication before he starts mumbling het again
>>about astrologers, axial rotation, apparent frames of reference and
>>whatever else I may have missed.
>>
>>Clear skies!
>>
>>Anthony.
>
>
> .
>
> The Roemerian insight on the astronomical adjustment know as the
> Equation of Light is based on orbital comparisons just as Kepler's
> refinement of orbital geometries is based on orbital comparisons.
<snip>
>
> Go back to occultations,personally I think birdwatching photography is
> far more difficult than what you do.At least the birdwatchers put
> thing in correct context.
>
Does this mean you will not be computing an estimated distance of the
moon from earth using this collaborative work so that we can compare
estimates?
The image scale of the resampled image is around 2.51"/pixel. ;-)
Anthony.
Shawn
Cool! Thanks to both of you for sharing.
Shawn
oriel36
>
> - Show quoted text -
Astronomers have made use of occultations and specifically using Io
and Jupiter -
http://www.lafterhall.com/io_occultation_020414_jferreira.jpg
Of course these astronomers worked with orbital comparisons between
Earth and Jupiter in determining the insight that the illusion of the
irregular motion of Io can be explained in terms of finite light
speed.As yuo creeps can't even acknowledge orbital comparisons between
the Earth and the other planets as the main argument for
heliocentricity,you are unlikely to appreciate the Keplerian and
Roemerian refinements of the system
You should be delighted that you are getting a free education,I would
show you where Newton was very naughty in bundling the Keplerian
insight on orbital geometries with the Roemerian insight on finite
light distance but I just find it funny nowadays -
"For to the earth they appear sometimes direct, sometimes stationary,
nay, and sometimes retrograde. But from the sun they are always seen
direct, and to proceed with a motion nearly uniform, that is to say,
a
little swifter in the perihelion and a little slower in the aphelion
distances, so as to maintain an equality in the description of the
areas. This a noted proposition among astronomers, and particularly
demonstrable in Jupiter, from the eclipses of his satellites; by the
help of which eclipses, as we have said, the heliocentric longitudes
of
that planet, and its distances from the sun, are determined." Newton
The nice thing is that modern imaging removes all the garbage of
Newton and exposes the real reasoning behind Copernican reasoning and
even the later refinements.So far you seem to detest astronomy and
what those images are telling you about not only the motions of the
other planets but also the motion of the Earth -
http://antwrp.gsfc.nasa.gov/apod/image/0112/jupsatloop_tezel.jpg
http://www.youtube.com/watch?v=o_fd8O1sk3I
You should enjoy how the faster orbital motion of the Earth accounts
for retrogrades of the outer planets and the faster orbital motion of
the inner planets overtaking the slower Earth accounts for
transits,all bound together in a common heliocentric orbit.
Until you learn that much,you are adhere to the damaging doctrine of
astrology.
Anthony Ayiomamitis
<snip>
>
> You should enjoy how the faster orbital motion of the Earth accounts
> for retrogrades of the outer planets and the faster orbital motion of
> the inner planets overtaking the slower Earth accounts for
> transits,all bound together in a common heliocentric orbit.
>
> Until you learn that much,you are adhere to the damaging doctrine of
> astrology.
>
Oriel,
I get an estimate of 438,988 km for the distance of the moon from the
earth when, in fact, it was 395,520 km at the time of photography. In
other words, there is an error of approximately 10%.
Clear skies!
Anthony.
Ernie Wright
>>>>> http://www.perseus.gr/Astro-Lunar-Parallax.htm
>>>
>>> The image scale of the resampled image is around 2.51"/pixel. ;-)
>
> I get an estimate of 438,988 km for the distance of the moon from the
> earth when, in fact, it was 395,520 km at the time of photography. In
> other words, there is an error of approximately 10%.
I got an estimate of 443,368 km. This is assuming an image scale of
about 3.25"/pixel, which I got from the diameter of the Moon,
557 pixels using the ruler tool in Photoshop CS2
1812" according to http://aa.usno.navy.mil/data/docs/diskmap.html
The distance between the two images of Regulus is 337 pixels = 1096".
Moon distance = (Selsey Athens distance / 2) / tan(1096"/2)
I think the error comes from assuming that the Selsey-Athens base of the
triangle is at right angles to the Earth-Moon vector. In general it
won't be. If tilting that line up to make it perpendicular shortens it
to about 2100 km, we get a very accurate estimate.
- Ernie http://home.comcast.net/~erniew
oriel36
You openly mock the methods of astronomers,first the Copernican
insight based on the orbital motion of the Earth,then Kepler's use of
orbital comparisons between Earth and Mars to determine a more refined
orbital geometry and the Romerian Equation of Light insight based on
orbital comparisons between Earth and Jupiter.
The motion of the visble stars of our galaxy around a central axis
will change their orientation to the external galaxies,as you
creatures have the visible stars stuck on an astrological framework
there is no possibility of appreciating this great cycle,even in
principle.The appreciation of Milky Way stellar carousel should be a
matter of course along with the normal perception that the foreground
stars would alter their positions to the external galaxies but this is
the dark ages of astronomy and external galaxies are referenced off
the constellations and its celestial sphere geometry.
Successful people do not do this,men have always had clear geometric
judgements based on physical considerations to create some of the
great achievements of mankind but not this,not this astrological/
magnification exercise .You openly mock uygens treatise on how the 24
hour day is created from variations in the length of the daily cycle
determined at noon or rather the tremedous amount of effort by
civilisation after civilisation to refine the methods that now
constitute the clock/calendar system.
What is it with the English,did John Harrison not put you astrologers
to bed when he invented accurate clocks based on Huygens 24 hour/360
degree principles.The same miserable astrological atmosphere still
prevails not only on account of your stupid correlation between
clocks and axial rotation but the greatest Western astronomical
discovery of all - the Copernican heliocentric system.I well
understand Harrison's frustrations when faced with festering hypocrisy
and it is far worse today.,the difference is that I have the actual
images to show exactly what you lot are- astrologers with telescopes.
Richard Tobin
oriel36 <kellehe...@gmail.com> wrote:
>You openly mock the methods of astronomers,
No, we openly mock *you*.
Anthony Ayiomamitis
> In article <1180086672.7...@q69g2000hsb.googlegroups.com>,
> oriel36 <kellehe...@gmail.com> wrote:
>
>
>>You openly mock the methods of astronomers,
>
>
> No, we openly mock *you*.
AWESOME comeback. :-)
Anthony.
>
> -- Richard
Anthony Ayiomamitis
Thanks for the feedback Ernie. My results vary slightly due to SkyMap
Pro which indicates the moon had an apparent diameter of 1839.34" and
the parallax angle which I estimated to be 1113.6". My estimate as to
the distance also ignored the image scale I specified in an earlier post
which for some reason is not correct and I must check as to the reason(s).
Anyway, a nice exercise. Just ask Oriel.
Anthony.
>
> - Ernie http://home.comcast.net/~erniew
Ernie Wright
> [concerning http://www.perseus.gr/Astro-Lunar-Parallax.htm]
>
> Thanks for the feedback Ernie.
Thanks to you and Pete for a fascinating collaborative exercise!
I hope you'll forgive me now for blathering a bit, but it'll lead to a
much better estimate of the Moon's distance derived from your images.
We both got estimates of about 440,000 km, somewhat higher than the true
distance of about 396,000 km, and I mentioned yesterday that most of the
error is because the base of the triangle we're using, the line between
Selsey and Athens, is skewed. The base we *should* be using is a line
that directly faces the Moon.
The situation looks something like this:
. * Selsey
. \
. \ --------> to the Moon
. \
. * Athens
The base we should be using,
. * Selsey ....... |
. |
. | --------> to the Moon
. |
. * Athens ... |
is the projection of the Selsey-Athens line onto the image plane. Its
length is just the dot product of two vectors: the Selsey-Athens line and
the Earth-Moon line. To find the vectors, we need a common coordinate
system for Athens, Selsey, and the Moon.
I used geocentric equatorial coordinates. The r.a. and dec. of the Moon
are easy enough to find. The coordinates for the cities are just the r.a.
and dec. of the zenith at the time of the observation, which are the local
sidereal time and geographic latitude, respectively.
Convert these to cartesian coordinates in the usual way:
x = cos( dec ) * cos( ra )
y = cos( dec ) * sin( ra )
z = sin( dec )
Subtract the Athens (x, y, z) from the Selsey (x, y, z) and normalize
(divide by the vector length) to get a unit vector pointing from one to
the other. The dot product of this direction vector with the one for
the Moon is the cosine of the angle between them. The length of the
projection we want is the cosine of the difference between this angle
and 90 degrees.
When I did this, I got a length factor of 0.928. Multiplying this by the
chord length distance between Athens and Selsey (2356 km) gives a triangle
base of 2186 km. Using your (probably more careful than mine) estimate of
the parallax angle, 1113.6", yields a distance estimate of 404,897 km, for
an error of only a little more than 2%. That's pretty cool!
> Anyway, a nice exercise. Just ask Oriel.
Too bad Gerald's not equipped to appreciate it. It very much has the
flavor of the Ancient Greek efforts to measure the scale of the solar
system.
- Ernie http://home.comcast.net/~erniew
Anthony Ayiomamitis
> Anthony Ayiomamitis wrote:
>
>> [concerning http://www.perseus.gr/Astro-Lunar-Parallax.htm]
>>
>> Thanks for the feedback Ernie.
>
>
> Thanks to you and Pete for a fascinating collaborative exercise!
Ernie,
We thank you as well. I just hope you have generous bandwidth for your
website: http://www.lpod.org/?m=20070526
Anthony.
Khanh-Dang
>> [concerning http://www.perseus.gr/Astro-Lunar-Parallax.htm]
> The situation looks something like this:
>
> . * Selsey
> . \
> . \ --------> to the Moon
> . \
> . * Athens
>
> The base we should be using,
>
> . * Selsey ....... |
> . |
> . | --------> to the Moon
> . |
> . * Athens ... |
>
> When I did this, I got a length factor of 0.928. Multiplying this by the
> chord length distance between Athens and Selsey (2356 km) gives a triangle
> base of 2186 km. Using your (probably more careful than mine) estimate of
> the parallax angle, 1113.6", yields a distance estimate of 404,897 km, for
> an error of only a little more than 2%. That's pretty cool!
Well, actually, the 395,520 km Anthony gave is the geocentric distance
of the Moon, i.e. the distance from the center of the Earth to the
center of the Moon. In geocentric coordinates, the Moon is a little
closer. My ephemeris program tells me the real distance of the Moon from
Athens is 391,741 km, so that the error is around 3.4 %. That's still
cool, however ;-)
Ernie Wright
> Ernie,
>
> We thank you as well. I just hope you have generous bandwidth for your
> website: http://www.lpod.org/?m=20070526
Wow. Well, I guess I'll find out. :)
- Ernie http://home.comcast.net/~erniew
Ernie Wright
You're right, of course. And as it turns out, my first calculation,
which I did by hand, had an error in it (I switched sine and cosine in
the declination term of the coordinate conversions; I described this the
right way in my post but did it backwards). I've written a program to
run the calculation more rigorously and it finds a distance about 3%
*less* than the topocentric distance.
> That's still cool, however ;-)
Doing this calculation gives one a renewed appreciation for what
Hipparchus was able to accomplish before trigonometry was invented.
- Ernie http://home.comcast.net/~erniew
Brian Tung
> Doing this calculation gives one a renewed appreciation for what
> Hipparchus was able to accomplish before trigonometry was invented.
Modern trigonometry, yes, but they had similar and basically sufficient
mathematical tools.
Your point stands, though: Very impressive. Then again, of course, he
was Hipparchus, not some doof.
--
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.html
Quadibloc
> The motion of the visble stars of our galaxy around a central axis
> will change their orientation to the external galaxies,as you
> creatures have the visible stars stuck on an astrological framework
> there is no possibility of appreciating this great cycle,even in
> principle.
No. This is not the case.
Of course we can recognize that the "fixed" stars in the Milky Way
galaxy really do move, slowly.
Just as we realize that precession of the equinoxes is a real
phenomenon.
We still use the position of the equinoxes, or the "fixed stars", as a
background, as a reference frame, because they move so slowly that
they serve as *reasonably* fixed landmarks, but, naturally, a closer
approximation to an inertial frame *is* possible through using distant
galaxies as a reference.
Even the galaxies, though, are in motion.
But we are talking, as I noted in a previous post, about a matter of a
hundredth of a second per day, even with the largest correction, the
one for precession. The precession cycle takes about 24,000 years.
Compare that with the *one year* cycle that causes the difference
between the 24 hour synodic day and the 23 hour and 56 minute sidereal
day.
If you advocate adopting the system of Tycho Brahe because you are
annoyed that we sometimes ignore the small precession effect, you are
straining out a gnat yet swallowing a camel. If that is not what you
are doing, then your point is still a mystery to me.
John Savard
Ernie Wright
> Ernie Wright wrote:
>
>> Doing this calculation gives one a renewed appreciation for what
>> Hipparchus was able to accomplish before trigonometry was invented.
>
> Modern trigonometry, yes, but they had similar and basically sufficient
> mathematical tools.
Indeed. There's no mathematically important difference between using
sines and using chords.
> Your point stands, though: Very impressive. Then again, of course, he
> was Hipparchus, not some doof.
That's pretty much what I was trying to say. He didn't need *any* of
the tools I perhaps doofily relied on. And unlike us, he couldn't peek
at the answers in the back of the book.
As Brian already knows, almost none of Hipparchus's original writing has
survived. We have to rely mainly on the bits and pieces conveyed to us
by Ptolemy in the Almagest. Ptolemy's description of lunar parallax
calculations is in book V part 17. The diagram (Fig. 5.13 in Toomer's
translation) shows the situation pretty clearly.
- Ernie http://home.comcast.net/~erniew
Ernie Wright
I had a chance this weekend to do a few 3D renders showing the geometry
of the Earth-Moon system at the time of the images. They include a
stereo pair of the views from Athens and Selsey.
http://home.comcast.net/~erniew/astro/moonpar.html
I'll probably add some details to the text at the end of the page in the
next couple of days.
- Ernie http://home.comcast.net/~erniew
Pete Lawrence
wrote:
Ernie,
That's a fantastic write up - thanks for doing that.
--
Pete
http://www.digitalsky.org.uk
Anthony Ayiomamitis
Ditto from me as well!
Anthony.
Ernie Wright
> Pete Lawrence wrote:
>> Ernie Wright wrote:
>>> http://home.comcast.net/~erniew/astro/moonpar.html
>>
>> Ernie,
>> That's a fantastic write up - thanks for doing that.
>
> Ditto from me as well!
I'm very glad you guys like it. Thanks again to both of you for the
inspiration.
- Ernie http://home.comcast.net/~erniew