Neil and Simon's time lapse of the eclipse

[Stephen Guerin]

Nice writeup of capturing a timelapse of the eclipse in Santa Fe by Neil Pomerleau with Simon Mehalek:

  http://blog.neilpomerleau.com/posts/capturing-a-solar-eclipse/

-S

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[Mark Janssen]

Nice!  But here's a question:

How is it that the moon is sometimes only part of the size of the sun and othertimes blocks 100% of the sun (given the "standard" astronomical ides of the universe)?

Fair warning: this *is* a trick question.

Mark Janssen

gothenburg, nebr

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[Nicholas Thompson]

I had the same question.  Awaiting the trick answer. 

[Mark Janssen]

Oops, I meant to add (just to be clear) that the variance of the moon's angular displacement would not seem sufficient to account for it...

Mark

[Roger Critchlow]

Now you're really getting tricky.  The variance of the moon's angular displacement?  

The moon moves roughly 12 degrees a day, or half a degree an hour, the variation in that displacement around the mean value is the whole theory of the moon's motion.  I wouldn't call it a variance because it's not a random variable.  One's imperfect observations of the variation might have a variance, but the moon's motion has a deterministic variation, described by parameters written with a dozen significant digits.

But that probably isn't the "angular displacement" that you mean, so maybe you should add another clarification.

-- rec --

2012/5/21 Mark Janssen <dreamin...@gmail.com>

[Mark Janssen]

On Mon, May 21, 2012 at 11:14 AM, Roger Critchlow <r...@elf.org> wrote:

Now you're really getting tricky.  The variance of the moon's angular displacement?  

The moon moves roughly 12 degrees a day, or half a degree an hour, the variation in that displacement around the mean value is the whole theory of the moon's motion.  I wouldn't call it a variance because it's not a random variable.  One's imperfect observations of the variation might have a variance, but the moon's motion has a deterministic variation, described by parameters written with a dozen significant digits.

But that probably isn't the "angular displacement" that you mean, so maybe you should add another clarification.

I was referring to the angular displacement as defined by astronomy, but probably should have used the word "diameter" (cf. Wikipedia:angular_diameter).

mark 

[Mark Janssen]

Argh :*{ 

Pardon me, but please ignore my use of the word displacement.  I don't know what I was thinking...

*hastens out of the room before anyone notices*

mark

mark

[drew einhorn]

I observed the eclipse for the foothills on the east side of Albuquerque, and did not see these effects.  And they are not apparent in the many images available on the web.  

I was supposed to meet a friend with a telescope set up to project an image onto a screen.  But I did not find him in the crowd.

I observed using glasses distributed by many of the local museums.  What I saw was a round sun and a round moon blocking the sun.  Sunspots ragged edge of the moon were not visible without magnification.

So it is something specific to the either the equipment or the location.

Welding googles, glass, etc. are numbered on a scale from 1 to 14 with 14 being the darkest.  The recommendations for safely view the eclipse specify number 14.  Number 14 is rarely used in welding and not readily available.  I wonder if the light was too bright for the equipment.  And I wonder if the image sensor was damaged.  Have they checked it with a grey card.

It could be lens flare.

http://en.wikipedia.org/wiki/Lens_flare

If the light is too bright on the sensor adjacent pixels can be effected.

When the moon is in the center of the sun to bright ring is too wide making the moon look too small.

When the image should be a crescent things get more complicated.  But my gut feeling is there was just way too much light on the sensor.

There are clouds visible in the images and they are brightly lit and may have contributed to the spreading of the suns image.

Did Neil and SImon also view the eclipse through the widely available low tech glasses at their site?  Or did they only view it through their high tech gear?

All in all, I believe it's an artifact produced by their equipment.

I'm wondering what they were doing with the pan/tilt as the sun drops below the horizon it does not look like the camera direction is fixed and they are not actually tracking the sun.

Drew Einhorn

"You can see a lot by just looking."
  --  Yogi Berra

[Mark Janssen]

On Mon, May 21, 2012 at 11:36 AM, drew einhorn <drew.e...@gmail.com> wrote:

So it is something specific to the either the equipment or the location.

 

It could be lens flare.

http://en.wikipedia.org/wiki/Lens_flare

 

Did Neil and SImon also view the eclipse through the widely available low tech glasses at their site?  Or did they only view it through their high tech gear?

All in all, I believe it's an artifact produced by their equipment.

You may actually want to view the video.  You'll see that it could not have been a solar flare and the "adjacent pixel theory" would have more randomization, I think.  The sun disk is consistently much larger than the moon.   And you seem to be positing that their "high-tech equipment" is inferior to the "widely available low tech glasses".   Not sure how you would explain that...

mark

[drew einhorn]

The effects were not visible in Albuquerque using low tech gear or any of the other images I have seen on the web.

All high tech equipment and techniques need to be validated by comparing their results to other equipment and techniques.  Any differences need to be explained.

 

[drew einhorn]

On Mon, May 21, 2012 at 10:59 AM, drew einhorn <drew.e...@gmail.com> wrote:

On Mon, May 21, 2012 at 10:54 AM, Mark Janssen <dreamin...@gmail.com> wrote:

On Mon, May 21, 2012 at 11:36 AM, drew einhorn <drew.e...@gmail.com> wrote:

 

You may actually want to view the video.  You'll see that it could not have been a solar flare and the "adjacent pixel theory" would have more randomization, 

I did watch the video and it did not look like what I saw and what other folks photographed.

And I referenced "lens flare" not "solar flare".  To see solar flares we need a total eclipse not an annular eclipse.

And the effects vary through the progress of the video.  This could be your randomization.  And it's probably not random anyway.

I still think their imaging was overwhelmed by way too much light.

[Bruce Sherwood]

The solar eclipse was only annular, not total, because it happened to
occur at a time when the Moon in its slightly non-circular, elliptical
orbit was as far from the Earth as it gets (the so-called "apogee").

There's a close connection with the "super Moon" that occurred half a
month ago (half a Moon period ago), when the full Moon was unusually
bright because that full Moon happened to occur when the Moon was as
close to the Earth as it ever gets ("perigee").

Summary: Half a month ago the Moon was full -- it was opposite the
Earth from the Sun, and it happened to be very close to the Earth.
Sunday the Moon had come halfway around its orbit and was between the
Earth and the Sun, and it was very far from the Earth because of
course the farthest point ("apogee") is halfway around the elliptical
orbit from the nearest point ("perigee").

Ain't science grand?

Bruce

P.S. http://www.fourmilab.ch/earthview/pacalc.html shows times of
perigees and apogees.

[Arlo Barnes]

Well, I assume that what with troubleshooting and so on that this was a rather last-minute affair, and prone to errors/glitches (like not actually tracking) - I would be interested to see how the images they discarded turned out.
Judging from the description of which ranges were visible, I probably viewed the eclipse not too far away, but with considerably less equipment; I wished a bit for a camera, any camera, as the last triangle (sailship sail, as someone also in the party commented) of the sun descended over the horizon. For magnified viewing I had a somewhat broken Celestron yard telescope with attached solar filter, and for naked-eye viewing (to be done only in brief spurts) I had a concatenation of about six moon filters. Like Messieurs Pomerlau and Mehalek, I did have a pinhole card to project miniature images of the eclipse onto various surfaces.
To address the other conversation, some helpful links from Wikipedia: SuperMoon PerApoGee Libration Paths Diameter

And while I agree there was too much light in the images (overexposed?) the several-posts-above-linked lens flare is from internal reflections (why some of the artifacts seem polygonal depending on the optical assembly; an example: Flare) not too much light in the shot; instead, that may be Diffraction or Bloom.
I believe the ellipticities of the Earth's and more so the Moon's orbit accounts for much of the variance from eclipse to eclipse. There may be optical or psychological factors like the 'ring widening' mentioned above, but they are more minor. Compare MoonIllusion. Other phenomena of interest: can we actually see relief on the moon's edge with little magnification or is it just heat distortion? Coronae and prominences cannot be easily seen for eclipses other than total, but just how big would they be in comparison to the sun? 

-Arlo James Barnes