APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

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APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby APOD Robot » Mon Jul 03, 2017 4:05 am

Image The Summer Triangle over the Great Wall

Explanation: Have you ever seen the Summer Triangle? The bright stars Vega, Deneb, and Altair form a large triangle on the sky that can be seen rising in the northern spring during the morning, and rising in the northern fall during the evening. During summer months, the triangle can be found nearly overhead near midnight as three of the brightest stars on the sky. Featured here, along with the arch of the central band of our Milky Way Galaxy, the Summer Triangle asterism was captured this spring over the Great Wall of China. This part of the Great Wall, a World Culture Heritage Site, was built during the 6th century on the Yan Mountains. At the summit is Wangjinglou Tower from which, on a clear night, the lights of Beijing are visible in the distance.

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby neufer » Mon Jul 03, 2017 8:53 am

.
So...(despite being a stone's throw away from Beijing) one can still see space from the Great Wall :!:
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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby astrofleck » Mon Jul 03, 2017 11:34 am

The Summer Triangle would be SETTING, not "rising in the northern fall during the evening."

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby De58te » Mon Jul 03, 2017 6:09 pm

Don't claim to be an expert, but the Summer Triangle would be rising in the spring north in the evening. That way it would be in the zenith around midnight around the start of summer. It would be setting earlier and earlier as autumn passes until it sets with the Sun.

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby Ann » Mon Jul 03, 2017 6:40 pm

Where I live (latitude +55.60587), the Summer Triangle is glorious all autumn. It's splendid in the western part of the evening sky all of November, for example. On Christmas Day, December 25, Altair is admittedly getting a little low, but I can still see it.

The Summer Triangle is as high as it can get at midnight on August 11.

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby heehaw » Mon Jul 03, 2017 7:02 pm

Where I live (latitude +55.60587), the Sun ... http://latitudelongitude.org/se/malmoe/

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby neufer » Mon Jul 03, 2017 7:52 pm

Click to play embedded YouTube video.

astrofleck wrote:
The Summer Triangle would be SETTING,
not "rising in the northern fall during the evening."
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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby Boomer12k » Mon Jul 03, 2017 11:51 pm

The Wall kinda points right to it, don't it... Great shot, of the Great Wall, and Great Summer Triangle...

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby Ann » Tue Jul 04, 2017 5:28 am

The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.

In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.

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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby neufer » Tue Jul 04, 2017 2:22 pm

Ann wrote:
The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.

In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.

The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.
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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby alter-ego » Thu Jul 06, 2017 5:36 am

neufer wrote:
Ann wrote:
The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.

In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.

The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.

You've underestimated the latitude range of year-long visibility by about 16°.
The closest the Sun gets to Altair (an thus the most limiting condition for Summer Triangle visibility for northern latitudes) occurs on Jan 21 or 22. For latitude ~26°N, Altair rises when the Sun is ~18° below the horizon, and is further below the horizon for all latitudes north of 26°N. Of course for latitudes <26°N, the Sun gets closer, eventually leading to periods of invisibility during the year.
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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby neufer » Thu Jul 06, 2017 7:24 am

alter-ego wrote:
neufer wrote:
The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.

You've underestimated the latitude range of year-long visibility by about 16°.
The closest the Sun gets to Altair (an thus the most limiting condition for Summer Triangle visibility for northern latitudes) occurs on Jan 21 or 22. For latitude ~26°N, Altair rises when the Sun is ~18° below the horizon, and is further below the horizon for all latitudes north of 26°N. Of course for latitudes <26°N, the Sun gets closer, eventually leading to periods of invisibility during the year.

I knew I was being conservative but my statement is technically not wrong (for a change).

(I also took the most limiting condition for the Summer Triangle as being four days earlier than Jan 21/22.)
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Re: APOD: The Summer Triangle over the Great Wall (2017 Jul 03)

Postby alter-ego » Fri Jul 07, 2017 3:51 am

neufer wrote:I knew I was being conservative but my statement is technically not wrong (for a change).

(I also took the most limiting condition for the Summer Triangle as being four days earlier than Jan 21/22.)

Yeah, I certainly wasn't intending to demean or judge your estimate. I thought you might be interested in a more accurate answer.
Nice job with that, btw.
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