Starship Asterisk*

alter-ego wrote: ↑Tue May 01, 2018 3:24 am

Gravitational Starlight Deflection Measurements during the 21 August 2017 Total Solar Eclipse wrote:

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Precise starlight positions near the sun were measured during the 21 August 2017 total solar eclipse in order to measure their gravitational deflections. The equipment, procedures, and analysis are described in detail. A portable refractor, a CCD camera, and a computerized mount were set up in Wyoming. Detailed calibrations were necessary to improve accuracy and precision. Nighttime measurements taken just before the eclipse provided cubic optical distortion corrections. Calibrations based on star field images 7.4 deg on both sides of the sun taken during totality gave linear and quadratic plate constants. A total of 45 images of the sky surrounding the Sun were acquired during the middle part of totality, with an integrated exposure of 22 seconds. The deflection analysis depended on accurate star positions from the USNO's UCAC5 star catalog. The final result was a deflection coefficient L = 1.752 arcsec, compared to the theoretical value of L = 1.751 arcsec, with an uncertainty of only 3%.
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The recent 21 August 2017 total solar eclipse across the United States provided a convenient opportunity to repeat this experiment. This paper reports successful starlight deflection measurements performed in Wyoming using high quality amateur astronomical equipment. The final results show the most precise and accurate measurements of this kind ever reported.

Done with 100mm aperture (stopped down to 87mm), and 543mm focal length, (comparison images taken within 1 minute before and after totality) these results are 2x better that the best previous measurements made in the 60's and 70's when the best technology provided "large photographic plates (0.2 m to 0.45 m), long refractor telescopes (1.5 m to 8.5 m focal length), and comparison images taken with the same telescope a few months before or after the eclipse to determine non-perturbed star positions."

Nice work by Donald Bruns. The S&T article: A Picture-Perfect Solar Eclipse Experiment by D. Bruns is informative and an easy read.

https://en.wikipedia.org/wiki/Brun%27s_theorem wrote:
<<In number theory, Brun's theorem states that the sum of the reciprocals of the twin primes (pairs of prime numbers which differ by 2) converges to a finite value known as Brun's constant, usually denoted by B2 (sequence A065421 in the OEIS). Brun's theorem was proved by Viggo Brun in 1919, and it has historical importance in the introduction of sieve methods. In 2002 Pascal Sebah and Patrick Demichel used all twin primes up to 10¹⁶ to give the estimate:

B2 ≈ 1.902160583104 =

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neufer wrote: ↑Mon Apr 30, 2018 4:20 pm

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MarkBour wrote: ↑Mon Apr 30, 2018 3:59 pm
Think about Albert Einstein's famous request, what is the star closest to the Sun that anyone photographed during this eclipse, I wonder?

In this image, I see one at about the 8-o'clock position, but it is not very close in.

Due to atmospheric distortion no one has improved all that much on Eddington using visible light from the ground (and getting closer to the Sun doesn't help a lot).

Gravitational Starlight Deflection Measurements during the 21 August 2017 Total Solar Eclipse wrote: Precise starlight positions near the sun were measured during the 21 August 2017 total solar eclipse in order to measure their gravitational deflections. The equipment, procedures, and analysis are described in detail. A portable refractor, a CCD camera, and a computerized mount were set up in Wyoming. Detailed calibrations were necessary to improve accuracy and precision. Nighttime measurements taken just before the eclipse provided cubic optical distortion corrections. Calibrations based on star field images 7.4 deg on both sides of the sun taken during totality gave linear and quadratic plate constants. A total of 45 images of the sky surrounding the Sun were acquired during the middle part of totality, with an integrated exposure of 22 seconds. The deflection analysis depended on accurate star positions from the USNO's UCAC5 star catalog. The final result was a deflection coefficient L = 1.752 arcsec, compared to the theoretical value of L = 1.751 arcsec, with an uncertainty of only 3%.
...
The recent 21 August 2017 total solar eclipse across the United States provided a convenient opportunity to repeat this experiment. This paper reports successful starlight deflection measurements performed in Wyoming using high quality amateur astronomical equipment. The final results show the most precise and accurate measurements of this kind ever reported.

neufer wrote: ↑Mon Apr 30, 2018 7:42 pm

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Ulysses observations of solar wind speed as a function of helio latitude during solar minimum. Slow wind (~400 km/s) is confined to the equatorial regions, while fast wind (~750 km/s) is seen over the poles. Red/blue colours show inward/outward polarities of the heliospheric magnetic field.

FLPhotoCatcher wrote: ↑Mon Apr 30, 2018 6:52 pm
Looking at the magnetic field lines, I notice a big difference between them near the poles vs equator. It seems like any charged particles escaping the sun near the equator would be moving slower because they would have to cross the magnetic field lines in a more perpendicular direction. And don't the denser magnetic field lines near the equator attract charged particles from the more polar regions? Might these things explain the barrel shape of "planetary nebulae"?

MarkBour wrote: ↑Mon Apr 30, 2018 3:59 pm
Think about Albert Einstein's famous request, what is the star closest to the Sun that anyone photographed during this eclipse, I wonder?

In this image, I see one at about the 8-o'clock position, but it is not very close in.

heehaw wrote: ↑Mon Apr 30, 2018 9:38 am "... will be in 2019 July" Oh, how I approve of THAT way of expressing the time! For example, today is: 2018 April 30 Monday. And not 4/30/18 which is our usual American way: leading to dates such as 1/3/9. And in England I believe one writes 30/4/18 ?

Roger wrote: ↑Mon Apr 30, 2018 5:18 amBut could you explain what are the two bright dots on top left?