APOD: Stars Trail over Ragusa (2020 Mar 28)

[APOD Robot]

Stars Trail over Ragusa

Explanation: In trying times, stars still trail in the night. Taken on March 14, this night skyscape was made by combining 230 exposures each 15 seconds long to follow the stars' circular paths. The camera was fixed to a tripod on an isolated terrace near the center of Ragusa, Italy, on the island of Sicily. But the night sky was shared around the rotating planet. A friend to celestial navigators and astrophotographers alike Polaris, the north star, makes the short bright trail near the center of the concentric celestial arcs.

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[Ann]

Star trail images are educational, since they demonstrate the fact that the Earth rotates around its axis, so that the sky appears to rotate around us.

What is the cluster of stars at left? I might be tempted to guess the Pleiades. But surely they are not so northerly placed in the Earth's sky?

Ann

[Joe Stieber]

What is the cluster of stars at left? I might be tempted to guess the Pleiades. But surely they are not so northerly placed in the Earth's sky?

Ann

I'm not that good at picking things out of star-trail images, but I suspect it's the Alpha Persei Cluster, roughly 40° from the north celestial pole. From a darker site, it's a fine view in binoculars, and even with unaided eyes, a clump of stars pops out with averted vision.

[Case]

Click to view full size image

When zoomed in, the individual exposures seem to be resolved. Fascinating! Not sure why they’re stripes instead of dots.

From the angle of the arcs (about 24.5°), I deduce 98 minutes between beginning and end.

[GeoXXX]

Like the aircraft landing trials at the bottom!

[Dzames]

Beautiful 24 hour trails. Since Italy is south of the Arctic circle, amazing how the daytime stars came out! Or was March 14 a looong sun eclipse day?

[neufer]

When zoomed in, the individual exposures seem to be resolved. Fascinating!
Not sure why they’re stripes instead of dots.

• Camera detector pixelation

[orin stepanek]

Star trail images are educational, since they demonstrate the fact that the Earth rotates around its axis, so that the sky appears to rotate around us.

What is the cluster of stars at left? I might be tempted to guess the Pleiades. But surely they are not so northerly placed in the Earth's sky?

Ann

Hi, Ann; I guess I am not smart enough to determine star clusters from circular star trails! I do love the Pleiades though! I guess that is one reason I got into APOD; The views are of endless beautiful astronomy photographs!

[Ann]

What is the cluster of stars at left? I might be tempted to guess the Pleiades. But surely they are not so northerly placed in the Earth's sky?

Ann

I'm not that good at picking things out of star-trail images, but I suspect it's the Alpha Persei Cluster, roughly 40° from the north celestial pole. From a darker site, it's a fine view in binoculars, and even with unaided eyes, a clump of stars pops out with averted vision.

Of course! Thank you, Joe Stieber!

Alpha Persei Cluster. The bright central star
is Mirfak. Image: Naoyuki Kurita.

Constellation Perseus with Alpha Persei Moving Cluster in the center. Photo: Tony Hallas.

---

[Ann]

Star trail images are educational, since they demonstrate the fact that the Earth rotates around its axis, so that the sky appears to rotate around us.

What is the cluster of stars at left? I might be tempted to guess the Pleiades. But surely they are not so northerly placed in the Earth's sky?

Ann

Hi, Ann; I guess I am not smart enough to determine star clusters from circular star trails! I do love the Pleiades though! I guess that is one reason I got into APOD; The views are of endless beautiful astronomy photographs!

I agree with you, Orin! Stunning astronomy images are the best!

Ann

[ta152h0]

I tried that w/my Nikon 3300 at 48 degrees North, 122 degrees West and I got a nice picture of star trails around Polaris. By the way, is laser light a sign wave with very high amplitude? pass the ice cold one.

[Dr Cozens]

Giovanni Battista Hodierna lived at Ragusa and made one of the first catalogs of star clusters in the 1650s.

[neufer]

By the way, is laser light a sign wave with very high amplitude?

• No

sine (n.) trigonometric function, 1590s (in Thomas Fale's "Horologiographia, the Art of Dialling"), from Latin sinus "fold in a garment, bend, curve, bosom" (see sinus). Used mid-12c. by Gherardo of Cremona in Medieval Latin translation of Arabic geometrical text to render Arabic jiba "chord of an arc, sine" (from Sanskrit jya "bowstring"), which he confused with jaib "bundle, bosom, fold in a garment."

Click to play embedded YouTube video.

sign (n.) early 13c., "gesture or motion of the hand," especially one meant to communicate something, from Old French signe "sign, mark," from Latin signum "identifying mark, token, indication, symbol; proof; military standard, ensign; a signal, an omen; sign in the heavens, constellation." Watkins compares Hebrew sakkin, Aramaic sakkin "slaughtering-knife," and mentions a theory that "both words are probably borrowed from an unknown third source."

It has ousted native token. Meaning "a mark or device having some special importance" is recorded from late 13c.; that of "a miracle" is from c. 1300. Zodiacal sense in English is from mid-14c. Sense of "characteristic device attached to the front of an inn, shop, etc., to distinguish it from others" is first recorded mid-15c. Meaning "token or signal of some condition" (late 13c.) is behind sign of the times (1520s). In some uses, the word probably is a shortening of ensign.>>

ensign (n.) early 15c., "a token, sign, symbol; badge of office, mark or insignia of authority or rank;" also "battle flag, flag or banner of a ship or troop of soldiers," via Scottish, from Old French enseigne (12c.) "mark, symbol, signal; flag, standard, pennant," from Latin insignia (plural); see insignia, which is a doublet of this word. As the word for the soldier who carries the flag, 1510s.

Laser-Driven Particle Accelerators
Science 21 Apr 2006: by Mike Dunne*

<<Laser acceleration of protons occurs as a result of the extremely high electric field gradients created on either the front or rear surface of thin foils illuminated by subpicosecond laser pulses, whose focused intensities exceed 10¹⁸ W cm⁻². The laser ionizes and subsequently accelerates electrons to relativistic velocities. These are confined to form a beam by the azimuthal magnetic field created in the interaction. The ensuing charge separation sets up the electric field to accelerate the proton or ion species in the foil, with an overall energy efficiency between 1 and 10%. Although such laser intensities are incredibly high, they are now routinely produced at high repetition rate on table-top-sized systems. This reflects the dramatic progress seen in laser technology, where an order-of-magnitude increase in peak laser power has been achieved roughly every 3 years.>>

[DonB312]

Beautiful 24 hour trails. Since Italy is south of the Arctic circle, amazing how the daytime stars came out! Or was March 14 a looong sun eclipse day?

The APOD description states "this night skyscape was made by combining 230 exposures each 15 seconds long"

230 * 15 = 3450 seconds
3450 / 60 = 57.5 minutes
57.5 / 60 = 0.96 hours

So this is a 1 hour star trail image rather than 24 hours.

Don

[MarkBour]

By the way, is laser light a sign wave with very high amplitude?

• No

I studied sign waves in my trig class:

Sorry, don't you hate GIFs that won't stop?

[TheZuke!]

[...] By the way, is laser light a sign wave with very high amplitude? [...]

As neufer answered correctly, "NO!"

LASER light is "coherent", all the photons are at the same [i.e. very close to the same] _frequency_.
Each fundamental colour of light has its own frequency, or often described in its wavelength (1/frequency) in nanometres.
The photons of a laser beam can be likened to a soldiers marching in formation, whereas incoherent light photons would more resemble
the runners in the Boston Marathon (except in all running toward the Finish Line, they are running in all directions (unless reflected or focused) away from the Starting Line (point source).

[Chris Peterson]

[...] By the way, is laser light a sign wave with very high amplitude? [...]

As neufer answered correctly, "NO!"

LASER light is "coherent", all the photons are at the same [i.e. very close to the same] _frequency_.
Each fundamental colour of light has its own frequency, or often described in its wavelength (1/frequency) in nanometres.
The photons of a laser beam can be likened to a soldiers marching in formation, whereas incoherent light photons would more resemble
the runners in the Boston Marathon (except in all running toward the Finish Line, they are running in all directions (unless reflected or focused) away from the Starting Line (point source).

The spatial and temporal coherence of laser light goes beyond simply having the same wavelength. You can easily create light of a single wavelength with a filter, but that light won't be coherent. That also requires that the photons be in phase with each other. That's only possible if they have the same wavelength, but it is the phase relationship that gives laser light most of its interesting properties.

[TheZuke!]

The spatial and temporal coherence of laser light goes beyond simply having the same wavelength. You can easily create light of a single wavelength with a filter, but that light won't be coherent. That also requires that the photons be in phase with each other. That's only possible if they have the same wavelength, but it is the phase relationship that gives laser light most of its interesting properties.

Agreed!

[neufer]

The spatial and temporal coherence of laser light goes beyond simply having the same wavelength. You can easily create light of a single wavelength with a filter, but that light won't be coherent. That also requires that the photons be in phase with each other. That's only possible if they have the same wavelength, but it is the phase relationship that gives laser light most of its interesting properties.

Agreed!

Laser-Driven Particle Accelerators
Science 21 Apr 2006: by Mike Dunne*

<<Laser acceleration of protons occurs as a result of the extremely high electric field gradients created on either the front or rear surface of thin foils illuminated by subpicosecond laser pulses, whose focused intensities exceed 10¹⁸ W cm⁻². The laser ionizes and subsequently accelerates electrons to relativistic velocities. These are confined to form a beam by the azimuthal magnetic field created in the interaction. The ensuing charge separation sets up the electric field to accelerate the proton or ion species in the foil, with an overall energy efficiency between 1 and 10%. Although such laser intensities are incredibly high, they are now routinely produced at high repetition rate on table-top-sized systems. This reflects the dramatic progress seen in laser technology, where an order-of-magnitude increase in peak laser power has been achieved roughly every 3 years.>>

[Dzames]

Don,

Yes, thank you. I was very wrong. For some reason I read the explanation as a full day. Sorry.

[Ann]

Ragusa, chocolate from Switzerland.

---

Ragusa, beautiful city of Sicily. Source: https://wsimag.com/food-and-wine/25768-amazing-sicily

---

Before the Öresund Bridge opened on July 1, 2000, people crossed the Strait of Öresund between Malmö and Copenhagen by hydrofoil. It took some 25 minutes, if I remember correctly.

During the crossing, I would often have a cup of coffee and a bar of Ragusa. Yum!

Of course, the Ragusa we had with our coffee came from Switzerland, unlike the Ragusa of today's APOD, which is both a city and a province in Sicily, Italy.

Ann

[felix_wegerer]

The first time I shot star trails around polaris I was impressed. I knew already that the stars will have a circular path around the north star but seeing it like this the first time was interesting!

[Gotthard]

Hi all you friends of star trails,

that is a nice image of a startrail, indeed. And it's worth to become an APOD, indeed too!

But ... how long will it still last that it's possibel that such images can be taken???

I fear ... the time already is over!

Two days before this star trail over ragusa became APOD I asked Mr. Nemiroff, if he could consider to choose an absolute impressive photography of star trails ... taken by Debra Ceravolo from Canada:



that she had postet on astrobin.

https://www.astrobin.com/khfb6v/0/

It's a pity, that this star trails had not been chosen ... maybee ... Mr. Musk and his economic interests should not have been criticised ...

Take your star trails now ... it could be the last chance ....

Be safe and ... clear skies ... ooops ... clearup skies! )

[Chris Peterson]

Hi all you friends of star trails,

that is a nice image of a startrail, indeed. And it's worth to become an APOD, indeed too!

But ... how long will it still last that it's possibel that such images can be taken???

I fear ... the time already is over!

Two days before this star trail over ragusa became APOD I asked Mr. Nemiroff, if he could consider to choose an absolute impressive photography of star trails ... taken by Debra Ceravolo from Canada:



that she had postet on astrobin.

https://www.astrobin.com/khfb6v/0/

It's a pity, that this star trails had not been chosen ... maybee ... Mr. Musk and his economic interests should not have been criticised ...

Take your star trails now ... it could be the last chance ....

Be safe and ... clear skies ... ooops ... clearup skies! :))

These satellites are in low Earth orbit. In most places, for most of the year, they are only visible near sunset or sunrise. Plenty of opportunities to take star trail images without them... although images with them are interesting, too.

[Gotthard]

Hi Chris, many thanks for your annotation. But there now is a request.

You are sure, that starlink is nearly invisible? Maybe, there will be ca. 7000 in LEO at a hight of appr. 340 km. But there will also be 1500 at an orbit of 550 km and 2500 at 1200 km. And ... why is the ISS on an LEO-orbit of 350 to 400km visible always, worldwide and even at midnight? Fake pictures and observations? And the photo of Debra Ceravolo ... is it manipulation ... photoshop? And your last annotation "interesting, too" ... should I change my observatory to a location near to an airport to get more interesting astrophotos?

I recommend to take the problem with starlink seriously!

Gotthard