APOD: Scintillating (2011 Apr 28)

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APOD: Scintillating (2011 Apr 28)

Post by APOD Robot » Thu Apr 28, 2011 4:06 am

Image Scintillating

Explanation: On June 4, 2010 Regulus, alpha star of the constellation Leo, and wandering planet Mars were at about the same apparent brightness, separated on the sky by 1.5 degrees. An ingenious and creative 10 second exposure from a swinging camera recorded these gyrating trails of the celestial pairing. Can you tell which trail belongs to the star and which to the planet? Hint: atmospheric turbulence causes the image of the star to scintillate or vary in brightness and color more readily than the planet. The scintillation is more pronounced because the star is effectively a point source of light seen as a narrow bundle of light rays. Rapidly changing refraction due to turbulence along the line of sight affects different colors of light by different amounts and generally produces a twinkling effect for stars. But Mars is much closer than the distant stars and an extended source of light. Though tiny, its disk is seen as a bundle of light rays that is substantially broader compared to a star's and so, on average, less affected by small scale turbulence. The result is the varied, rainbow like trail for Regulus (left) and the steadier, consistently reddish trail for Mars.

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Re: APOD: Scintillating (2011 Apr 28)

Post by bactame » Thu Apr 28, 2011 4:58 am

Looks like 9.5 cycles of the compound swing, the half cycle because the two ends of the patterns are on opposite sides of the figure. Guess i was hoping the width and height of the figure might have some significance but the width is the camera body contribution to motion and the height of the figure is the lens contribution to motion. The width of the lines are essentially the same and must mostly be a film sensitivity characteristic. So only the scintillation is left.

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Re: APOD: Scintillating (2011 Apr 28)

Post by owlice » Thu Apr 28, 2011 5:22 am

I think this is a very cool image! Along similar lines, an image which shows Sirius's colors is on a Recent Submissions thread here; have to scroll down a bit to see it.
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Re: APOD: Scintillating (2011 Apr 28)

Post by Art Felsinger » Thu Apr 28, 2011 7:11 am

Another observation is that the exposure started on the upper right which goes down to the greatest elongation and the end of the exposure is on the lower area slightly to the left.

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Re: APOD: Scintillating (2011 Apr 28)

Post by mastrulo » Thu Apr 28, 2011 9:39 am

don't get it!
Where is the science, how can any of the presented "photos" be taken seriously, it's 2 "points of light" heavily 'photoshopped' to remove all other points? What was done to enhance the scintillating, and 'a clever use of a swinging camera?'
As I said.
I simply don't get it.
APOD, Astronomy Picture of the Day?
Let's swing on the roller coaster with an open shutter, then use an application to make it look like we want and viola! iIt becomes a new branch of Astronomy.
Can we see a non swinging camera with a 10 second shutter and compare the results? I would of course ask than nothing be 'retouched' nor enhanced.
Disappointed.
Tony Mastrullo.

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Re: APOD: Scintillating (2011 Apr 28)

Post by Indigo_Sunrise » Thu Apr 28, 2011 10:35 am

Geez, whiner! (I would've said whiners, but:)
mastrulo wrote:don't get it!
Where is the science, how can any of the presented "photos" be taken seriously, it's 2 "points of light" heavily 'photoshopped' to remove all other points? What was done to enhance the scintillating, and 'a clever use of a swinging camera?'
As I said.
I simply don't get it.
APOD, Astronomy Picture of the Day?
Let's swing on the roller coaster with an open shutter, then use an application to make it look like we want and viola! iIt becomes a new branch of Astronomy.
Can we see a non swinging camera with a 10 second shutter and compare the results? I would of course ask than nothing be 'retouched' nor enhanced.
Disappointed.
Tony Mastrullo.
Guest wrote:I don't get it!
Where is the science, how can any of the presented "photos" be taken seriously, it's 2 "points of light" heavily 'photoshopped' to remove all other points? What was done to enhance the scintillating, and 'a clever use of a swinging camera?'
As I said.
I simply don't get it.
APOD, Austronomy Picture of the Day?
Let's swing on the roller coaster with an open shutter, then use an application to make it look like we want and viola! iIt becomes a new branch of Astronomy.
Can we see a non swinging camera with a 10 second shutter and compare the results? I would of course ask than nothing be 'retouched' nor enhanced.
Disappointed.
Tony Mastrullo.
Why post the same thing twice, under different user names? And within four minutes of each other? We get it, you're disappointed. :roll:
Well, as has been said before, "you can always come back tomorrow......."


I think this is a pretty unique and different image, with some interesting links included.
And I've always liked the word, scintillating'!
Hooray for today's APOD!!!!!

:mrgreen:
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Re: APOD: Scintillating (2011 Apr 28)

Post by neufer » Thu Apr 28, 2011 10:37 am

http://en.wikipedia.org/wiki/Lissajous_curve wrote: ImageImage
In mathematics, a Lissajous curve or Bowditch curve is the graph of a system of parametric equations:

Image

which describe complex harmonic motion. This family of curves was investigated by the American mathematician & astronomer Nathaniel Bowditch in 1815, and later in more detail by Jules Antoine Lissajous in 1857. The visual form of these curves is often suggestive of a three-dimensional knot, and indeed many kinds of knots, including those known as Lissajous knots, project to the plane as Lissajous figures.

Lissajous figures where a = 1, b = N and Image are Chebyshev polynomials of the first kind of degree N.
In orbital mechanics, a Lissajous orbit, is a quasi-periodic orbital trajectory that an object can follow around a Lagrangian point of a three-body system without requiring any propulsion. Lyapunov orbits around a libration point are curved paths that lie entirely in the plane of the two primary bodies. In contrast, Lissajous orbits include components in this plane and perpendicular to it, and follow a Lissajous curve. Halo orbits also include components perpendicular to the plane, but they are periodic, while Lissajous orbits are not.

A purely mechanical application of a Lissajous curve with a=1, b=2 is in the driving mechanism of the Mars Light type of oscillating beam lamps popular with railroads in the mid-1900s. The beam in some versions traces out a lopsided figure-8 pattern with the "8" lying on its side.>>
http://en.wikipedia.org/wiki/Mars_Light wrote: <<Mars Lights are signal-safety lights used in the United States and built by Mars Signal Light Company for railroad locomotives and fire apparatus. Mars Lights used a variety of means to cause the light to oscillate vertically, horizontally, or both, to catch the attention of motorists and pedestrians.

Mars lights were developed by Jerry Kennelly, a Chicago firefighter who realized that oscillating lamps would benefit fire departments and railroads. He performed an operational test with the C&NW railroad in 1936, and Mars Lights began appearing on locomotives in the 1940s.

The name "MARS" Light originated when the Mars Candy Company took over design and production. The majority of funding was provided by Mars, and they insisted that it carry the MARS name. It has nothing to do with "the light from Mars"
.>>
Art Neuendorffer

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Re: APOD: Scintillating (2011 Apr 28)

Post by owlice » Thu Apr 28, 2011 11:12 am

neufer, (Mr. Added Value), thanks for the additional information! I haven't thought about Lissajous curves in I don't know how long... long enough to have forgotten why I used to think of them, certainly.

Indigo, I agree with you. I like the image, the creativity in showing us something a different way, and the explanation and links. All around, a big HURRAY!!!
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Re: APOD: Scintillating (2011 Apr 28)

Post by orin stepanek » Thu Apr 28, 2011 11:22 am

Intriguing; Reminds me of something drawn with a Spirograph. :lol:
Orin

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Re: APOD: Scintillating (2011 Apr 28)

Post by neufer » Thu Apr 28, 2011 12:42 pm

owlice wrote:
neufer, (Mr. Added Value), thanks for the additional information!
I haven't thought about Lissajous curves in I don't know how long...
long enough to have forgotten why I used to think of them, certainly.
I think of them because they represent one of the simplest
examples of a functional power near a fixed point; as described in
my scintillating Journal of Mathematical Analysis and Applications article:

http://asterisk.apod.com/viewtopic.php? ... 06#p134528
Art Neuendorffer

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Re: APOD: Scintillating (2011 Apr 28)

Post by NoelC » Thu Apr 28, 2011 3:51 pm

It's a beautiful image! What a great way to show how the twinkling of a star differs from the relatively stable light of a planet.

I like the way the magnitude 4 K3 red star BSC 31 Leo also barely shows at the lower-left.

That was a relatively high focal length setup... Field of view is what, about 4 degrees?

-Noel

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Re: APOD: Scintillating (2011 Apr 28)

Post by StarCuriousAero » Thu Apr 28, 2011 5:33 pm

This is a beautiful image, and it doesn't look photoshopped at all, I have no idea what that guy was complaining about. You can actually see two additional stars, lower left AND lower right, but I have no idea which one it is, I'll refer that question to someone else.

Also, thank you Neufer for reminding me of Lissajou orbits, it's only been 2 years since I'd thought about them last but had already almost completely forgotten about them, haha. It's a shame I don't use more of the stuff I learned in college, but such is life. Pretty much any orbit utilizing the Lagrange points is pretty darned fascinating though, it's a shame they aren't used more often, YAY for JWST!! Can't wait for launch. :-D

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Re: APOD: Scintillating (2011 Apr 28)

Post by mitcoyote » Thu Apr 28, 2011 6:07 pm

Seems there's a far simpler way to explain Mars' apparently stable color in this view: most of the light coming from it is pink--that's why it's called the "Red Planet." Stars emit pretty much white light, which is to say very polychromatic. Yes, I know that Mars' colors are not uniform, but they tend strongly--at least in the visible--to cluster around pink/rust/salmon. You can diffract pink all you want, but you still get pink.

JH

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Re: APOD: Scintillating (2011 Apr 28)

Post by NoelC » Thu Apr 28, 2011 7:09 pm

mitcoyote wrote:Seems there's a far simpler way to explain Mars' apparently stable color in this view
Stable color, maybe, but not the much more stable luminance.

Turn the image to grayscale... Regulus varies hugely in brightness over time, while Mars is pretty solid...
LuminanceOnly.jpg
-Noel
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Re: APOD: Scintillating (2011 Apr 28)

Post by bystander » Thu Apr 28, 2011 7:21 pm

NoelC wrote:I like the way the magnitude 4 K3 red star BSC 31 Leo also barely shows at the lower-left.
There's also an image in the lower right.
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Re: APOD: Scintillating (2011 Apr 28)

Post by NoelC » Thu Apr 28, 2011 10:05 pm

bystander wrote:There's also an image in the lower right.
BSC 27 Nu Leo, Magnitude 5, almost as white as Regulus.

-Noel

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Re: APOD: Scintillating (2011 Apr 28)

Post by Ann » Thu Apr 28, 2011 11:38 pm

NoelC wrote:
bystander wrote:There's also an image in the lower right.
BSC 27 Nu Leo, Magnitude 5, almost as white as Regulus.

-Noel
Thanks, Noel! But Regulus isn't white, and neither is Nu. Both are B-type stars with slightly negative (blue) color indexes. But they are reddened by our atmosphere, which of course also causes the twinkling and the variations in brightness and in apparent hue.

An RGB image taken above the atmosphere would have shown Regulus and and Nu to be steady, both in hue (which would have been blue-white) and in brightness.

I agree with those who like this image. It is a very good illustration of the effect our atmosphere has on the light from stars. "Twinkle, twinkle little star" is a good description of what stars look like when you stand on the Earth looking up!

The twinkling is also a great way to separate stars from planets, which has already been pointed out. So if you ever see a really bright point of light in the sky that is really twinkling, and you are sure that it isn't Sirius, then you can start wondering if you have just seen a bright supernova in the sky!

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Re: APOD: Scintillating (2011 Apr 28)

Post by NoelC » Fri Apr 29, 2011 12:13 am

Yeah, I tend to flipflop between "astronomer's" white (Vega = color 0.0), and human white sometimes. :) Depends on whether I've been looking at astro charts.

-Noel

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Re: APOD: Scintillating (2011 Apr 28)

Post by Ann » Fri Apr 29, 2011 12:42 am

NoelC wrote:It's a beautiful image! What a great way to show how the twinkling of a star differs from the relatively stable light of a planet.

I like the way the magnitude 4 K3 red star BSC 31 Leo also barely shows at the lower-left.

That was a relatively high focal length setup... Field of view is what, about 4 degrees?

-Noel
Once more, thanks for pointing out both 31 Leo and Nu Leo, Noel! :D

31 Leo is indeed a reddish star. My software classifies it as a K4III star with a color index that is redder than that of Arcturus. It's funny, though, that 31 Leo looks brighter than Nu in the sky, but it is Nu that got the Greek letter while 31 only got the Flamsted designation! (Wonder if I spelled that correctly...? No, it should be Flamsteed. Drat.)

Ann
Last edited by Ann on Fri Apr 29, 2011 2:12 am, edited 1 time in total.
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Re: APOD: Scintillating (2011 Apr 28)

Post by mastrulo » Fri Apr 29, 2011 1:20 am

Indigo_Sunrise wrote:Geez, whiner! (I would've said whiners, but:)

Why post the same thing twice, under different user names? And within four minutes of each other? We get it, you're disappointed. :roll:
Well, as has been said before, "you can always come back tomorrow......."


I think this is a pretty unique and different image, with some interesting links included.
And I've always liked the word, scintillating'!
Hooray for today's APOD!!!!!

:mrgreen:
Hi,
I failed to login and I tried to delete the 'Guest' version after I logged in. Since I failed miserably, I thought by having my name to both and the second having logged in (I copy/Pasted) the text of me the guest, and my mind missed it, as I had intended to add as the first line to negate the guest, as it was in reality me. I see now I should've taken my time to better explain it, but if you look I signed both, I always do with my name.
Thank you for pointing it out, I thought it would've passed with the text being Identical and 'Guest' and me and both same signature would've sufficed. I have leaned another way, preview prior to and then it makes more sense.
Thank you.
Kindest Regards.
Tony Mastrullo.

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Re: APOD: Scintillating (2011 Apr 28)

Post by Chris Peterson » Fri Apr 29, 2011 2:25 am

Ann wrote:Thanks, Noel! But Regulus isn't white, and neither is Nu.
Note, however, that single-shot color cameras do not give very accurate representations of star colors. The color filters embedded in their sensors are not matched to the human eye, and the color conversion algorithms used are designed for terrestrial scenes, not astronomical ones. As a consequence, the color space of the camera is significantly different from that of the eye. In addition, it is easy for one or more channels to saturate, which further distorts the apparent color.

Even color indexes are not very good indicators of apparent color to the eye (except in extreme cases), since they are calculated by looking at the intensity of light at two or more broad spectral bands that have no relationship to the absorption spectra of the pigments in human cones.
Chris

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Re: APOD: Scintillating (2011 Apr 28)

Post by mitcoyote » Fri Apr 29, 2011 4:08 am

Noel--

Thanks. Gray scale makes a very clever difference.

Doesn't atmospheric attenuation = f(wavelength [= f (diffraction)]) account for "twinkling" here?
Thus if diffraction isn't much of a factor, then neither is wavelength, so neither would be attenuation,
so neither would be brightness. Or am I missing something?

JH

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Re: APOD: Scintillating (2011 Apr 28)

Post by Chris Peterson » Fri Apr 29, 2011 4:26 am

mitcoyote wrote:Doesn't atmospheric attenuation = f(wavelength [= f (diffraction)]) account for "twinkling" here?
Thus if diffraction isn't much of a factor, then neither is wavelength, so neither would be attenuation,
so neither would be brightness. Or am I missing something?
Diffraction is not involved. The twinkling is caused by refraction, and the refraction is caused by the variation in index of refraction (speed of light) as the air density varies due to high altitude winds. Neither are we seeing attenuation- the atmosphere has very low attenuation, except near the horizons.
Chris

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Re: APOD: Scintillating (2011 Apr 28)

Post by Ann » Fri Apr 29, 2011 5:04 am

Chris Peterson wrote:
Even color indexes are not very good indicators of apparent color to the eye (except in extreme cases), since they are calculated by looking at the intensity of light at two or more broad spectral bands that have no relationship to the absorption spectra of the pigments in human cones.
According to my experience, color indexes are good, although not perfect, indicators of apparent color to the eye. However, I'm talking about apparent star color to the eye when the star is observed through a moderately powerful telescope.

A star might possibly have a strong emission line somewhere in the visual spectrum, and then two broad spectral bands may not do a very good job of explaining what the star looks like to the eye. But by and large, I think color indexes are fairly reliable indicators of what the star would look like if it was bright enough to stimulate color response.

Most people agree that the Sun looks yellow. But that apparent color is created precisely because much of the Sun's blue light is scattered all over the sky through refraction by the atmosphere. So the Sun appears to be yellow (= white minus blue light), and the sky appears to be blue (= no light plus blue light).

In the same way that the Sun looks yellower than it would have done if we hadn't seen it through the atmosphere, in the same way Regulus looks yellower than it would have done if we hadn't seen it through the atmosphere.

Regulus is undoubtedly a bluish star, although its color is pale and anything but saturated.

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Re: APOD: Scintillating (2011 Apr 28)

Post by NoelC » Fri Apr 29, 2011 1:48 pm

Perhaps to help in understanding of why planets don't seem to twinkle, we should re-emphasize that the stars are tiny point light sources (from our perspective), while the planets actually have significant angular size. Not enough that you can see it with the naked eye, but certainly more than a star.

This is a short, repeating sequence of frames of Venus, taken at a high focal length through atmospheric conditions that were making the stars twinkle quite a bit (atmospheric refraction is responsible for the color fringing).

Image

Note that even though it's moving around quite a bit, and even getting larger/smaller sometimes, there are certain parts of the image that are always illuminated.

I need to take a similar sequence of images of a star some time to help make a better comparison. Until then, there is this page: http://apod.nasa.gov/apod/ap000725.html

Image

Note that you'll need to refresh the page to make the above image show its animation, as it's not set to repeat.
-Noel