Dark Sky poll

number of stars you can see at night, outdoors, with the unaided eye ... in the Orion constellation

0
2
40%
1 to 10
1
20%
11-20
1
20%
20-30
0
No votes
30+
1
20%
 
Total votes: 5

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ChrisGreaves
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Dark Sky poll

Post by ChrisGreaves »

The race to reclaim the dark

"A very simple way for people to get involved is to look up at the night sky and count the number of stars they can see in the Orion constellation," says Emma Marrington, CPRE's dark sky campaigner. "That can help build up a picture of what the nation's views are from the ground."

If you see 10 stars or fewer in one constellation, you are likely in an area with severe light pollution, notes Marrington. "But if you've got more than 30 stars, then you've got a truly dark sky."


In the poll I assume also cloudless night and so on.
Also that "in the Orion constellation" includes the stars that define the constellation, and then all other stars inside that boundary.
Cheers, Chris
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Graeme
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Re: Dark Sky poll

Post by Graeme »

We will have to wait until the winter for this one Chris, Orion is behind the sun at the moment.

In January Orion is due South and so at it's highest and darkest, at about 2200.

My avatar is the Orion nebula, the middle star in his sword.

Regards

Graeme

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Re: Dark Sky poll

Post by stuck »

ChrisGreaves wrote:
15 Jun 2022, 18:46
...CPRE's dark sky campaign...
I first heard of this campaign back in the winter and I did look out on a clear night but I can't remember how many stars I counted. By the time Orion is visible again I'll have forgotten about the campaign again, as well as this poll :laugh:

Ken

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Re: Dark Sky poll

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Graeme wrote:
15 Jun 2022, 21:58
We will have to wait until the winter for this one Chris, Orion is behind the sun at the moment.
Graeme, thanks for this news, I think.

I was outside this morning at 0308 and looked where Orion used to be and Lo! it was not there!
I have no belief in astrology ("Today something unexpected will happen!") but I do recall that according to birth dates, I am a Gemini; that is, that months of the year are tied to popular constellations of stars, which stars, by definition, must be within our galaxy.

I dropped back to sleep while listening to a self-administered presentation surrounding a simple model of The Milky Way with our Sun orbiting in the galactic plane and our Earth orbiting in the solar plane, seeing that at one time Earth lay between Sun and the galactic centre, and six months later Earth was positioned such that Sun lay between Earth and Galactic Centre.

That is, in its annual orbit around Sun, Earth's night-side pointedly swept like a searchlight in a circle around the entire galaxy.

The last thing I remember was the scale of three periods - of Earth's rotation (one day), of Earth's orbit (365 days), and Sun's orbit (200 million years).
Cheers, Chris
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Re: Dark Sky poll

Post by Graeme »

The sun moves from Taurus to Gemini next week so it must be your birthday soon! The solar system is a flat disc of planets orbiting the Sun, so the Sun, the Moon and the planets all appear to follow a line across the sky (give or take) called the ecliptic. The ecliptic goes through the 12 zodiac constellations plus Ophiuchus. The ecliptic is at 23° to the plane of the solar system and the plane of the solar system is inclined to the plane of the galaxy by 63°

The galactic centre is in Sagittarius and it's now thought that we orbit it every 150 million years.

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Re: Dark Sky poll

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Graeme wrote:
16 Jun 2022, 15:16
The sun moves from Taurus to Gemini next week so it must be your birthday soon!
Nah! You missed it by a mile. my birthday was over 51 weeks ago :flee:
... 12 zodiac constellations plus Ophiuchus.
Ophiuchus.png
I will migrate to Windows 2058 and Office 2059 before I will admit to seeing a man, let alone a snake, in the constellation Ophiuchus. I just checked, and the constellation bears a close resemblance to a scrunched up sheet of notepaper in my waste-paper basket. No way am I getting out of bed to crank up the heat again and at 0308 look at a snake-oil trick like this.
The ecliptic is at 23° to the plane of the solar system and the plane of the solar system is inclined to the plane of the galaxy by 63°
Now this I know, and for about a year now have been using it to explain why Canadian tourists are amazed at "the number of stars in Australia - the clear skies, you know" when Sydney, Melbourne, Perth and even Alice Springs(pop. 29,000) suffer from light pollution almost as bad as Bonavista's light pollution (pop 3,800).
The galactic centre is in Sagittarius and it's now thought that we orbit it every 150 million years.
Well I was quoting a well-established reference work (1m23s) which is how I remember important data and facts. Take it up with Eric Idle and John Du Prez.

I am now contemplating sun-dials between the tropics.
Cheers, Chris
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Re: Dark Sky poll

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Happy Birthday sometime soon, or very recently, Chris!!! :fanfare: :fanfare: :fanfare: :fanfare: :fanfare:
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Re: Dark Sky poll

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BobH wrote:
16 Jun 2022, 17:33
Happy Birthday sometime soon, or very recently, Chris!!! :fanfare: :fanfare: :fanfare: :fanfare: :fanfare:
Thank you, Uncle.
Your loving nephew, Chris
P.S. Why did you stop sending me ten-shilling postal orders? C
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Re: Dark Sky poll

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You moved. There is no postal service in Bonavista as it is at the end of the Earth! :grin:

Did you pass the eye test? :innocent:
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Re: Dark Sky poll

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ChrisGreaves wrote:
16 Jun 2022, 16:49
The ecliptic is at 23° to the plane of the solar system and the plane of the solar system is inclined to the plane of the galaxy by 63°
Now this I know, ....

I'm glad you spotted my deliberate mistake, the ecliptic is the plane of the solar system! And Earth's axis is inclined to it by 23°

Also,

Screenshot 2022-06-16 210648.jpg
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Re: Dark Sky poll

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Graeme wrote:
16 Jun 2022, 20:18
... the ecliptic is the plane of the solar system! And Earth's axis is inclined to it by 23°
Thank you, Graeme.
I just remember the "23" and "63" bits, add them to get 83, say that that is "almost 90", angle my hands a bit and everybody nods and says that yes, they can see that Sydney is staring into the galactic centre, and then they start discussing jam-making or something.

This morning at 0300 the moon was to the south, but very low in the sky. i think that this means that the plane of the moon's orbit around the earth is not the same plane as that of the planets around the sun. If our Moon's orbit plane was congruent with the planetary orbit's planes (including our planet), then different parts of the earth would see lunar and solar eclipses each month. That we do not see eclipses monthly is confirmation that the moon's orbital plane is not that of the planetary orbits plane.
And the planetary orbits plane is given the name "The Ecliptic". Is that close to the truth?
Cheers, Chris
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Re: Dark Sky poll

Post by Graeme »

The Ecliptic is the line across the sky that the sun follows as seen from the Earth. So it's higher in the summer during the day and in the winter during the night. As we are close to the June Solstice the ecliptic is quite low in the sky at night in the northern hemisphere. All the planets have orbits that are in the plane of the solar system but they all, to different degrees, have an angle of inclination to that of Earth's. So planets are always quite close to the ecliptic and at opposition planets can be at different elevations each year. This year Jupiter will be higher than it was last year so I will have my telescope pointing at it in September. The Moon's orbit is inclined to the ecliptic by 5°and so we don't get an eclipse every month. It takes about 27 days to complete a cycle so at the moment it is low in the sky, below the ecliptic(northern hemisphere). Between now and the end of June it will pass through a rising node and appear higher in the sky.

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Re: Dark Sky poll

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Graeme wrote:
17 Jun 2022, 12:13
The Ecliptic is the line across the sky that the sun follows as seen from the Earth.
Hi Graeme. If I may ...
Assume that I am seated in a fixed spot inside the house, staring through a window, and carrying a ten-foot long magic marker (or that I have a super camera with a timing device) and that I track the position of the sun as it passes my windows, 24/365. Each day, the sun would "draw a line" across my window or photographic plate. And as the seasons progress through a six-month cycle, the collection of sun-lines would form a band of light across the scene. I think that the sun-band would represent a 23+23=46º-wide arc across the sky, and hence, across my window-pane.
Is that correct?

The moon, too has an orbit that causes the moon to appear higher and lower in its travels, so that if I plotted the moon's passage 24/365, the moon too would describe a wide band across the window, although not at all necessarily the same 46º width of the arc of the sun's passage.

We know that the sun-arc and the moon-arc must coincide at some point, because both lunar and solar eclipses tell us that the sun and moon paths coincide across the face of the Earth.

Finally, in a third exercise I plot the paths of the eight planets across my window pane, collectively, those planets will mark a wide band across the pane.

We know that the planet Venus's individual band and the sun's band must coincide ("Transit of Venus") as must Mercury's ("Transit of Mercury").

So at this point I am left with three major bands of solar system travels, and both the moon band and the collective planetary band must coincide with the sun-band at some points.

I don't know what I am doing with this, except building a mental model in my head, like the 86º orientation of the Earth's axis.
Thanks for any elucidation
Chris
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Re: Dark Sky poll

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Graeme wrote:
17 Jun 2022, 12:13
... so we don't get an eclipse every month. I
And today I read "A total solar eclipse on Monday 8 April 2024 starts at 5:13PM local time and lasts almost three minutes. The chances of a clear sky are 25%. The track of totality is northeast from Mexico and Texas to Ohio, straddling the Canada–New England border, then across Maine, New Brunswick, Prince Edward Island and Newfoundland. So Bonavista is the final landward viewing point of this eclipse, which continues out into the Atlantic to be ended by sunset."

As I understand it our sky will go dark and then remain dark for about twelve hours!
Either that or our sky will be cloudy and then remain cloudy for about twelve hours!
Cheers, Chris
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Re: Dark Sky poll

Post by Graeme »

ChrisGreaves wrote:
19 Jun 2022, 06:42
Graeme wrote:
17 Jun 2022, 12:13
The Ecliptic is the line across the sky that the sun follows as seen from the Earth.
Assume that I am seated in a fixed spot inside the house, staring through a window,

This is already starting to sound a bit Plato! :smile:

Like this: (https://cloudappreciationsociety.org/shop/solarcan/)

SolarcanResults4.jpg

The width of a Moon image band would scale to 10° wide but your thought experiment needs a bit more thought to work out where it would sit on the Sun line because it's early here and I have still only had one coffee! I suppose they would coincide with the Moon arcs superimposed on the Sun arcs with a lower frequency and an additional 5° width top and bottom.


ChrisGreaves wrote:
19 Jun 2022, 06:42
Finally, in a third exercise I plot the paths of the eight planets across my window pane, collectively, those planets will mark a wide band across the pane.

We know that the planet Venus's individual band and the sun's band must coincide ("Transit of Venus") as must Mercury's ("Transit of Mercury").

So at this point I am left with three major bands of solar system travels, and both the moon band and the collective planetary band must coincide with the sun-band at some points.

They would all follow the Sun's band with each daily ecliptic line being the mean of all the planetary bands. Mercury would be the widest band.

Planetary inclination.png

I'm going to be late for work now. But there's always time for an early morning Chris planetary motion thought experiment!

Regards

Graeme
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Re: Dark Sky poll

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Graeme wrote:
20 Jun 2022, 06:18
I'm going to be late for work now.
All very well for you, but I am trying to drop off to sleep1 :evilgrin:
Thanks for the feedback. I shall mull a bit more.
Cheers, Chris
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Re: Dark Sky poll

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ChrisGreaves wrote:
19 Jun 2022, 23:12
Graeme wrote:
17 Jun 2022, 12:13
... so we don't get an eclipse every month. I
And today I read "A total solar eclipse on Monday 8 April 2024 starts at 5:13PM local time and lasts almost three minutes. The chances of a clear sky are 25%. The track of totality is northeast from Mexico and Texas to Ohio, straddling the Canada–New England border, then across Maine, New Brunswick, Prince Edward Island and Newfoundland. So Bonavista is the final landward viewing point of this eclipse, which continues out into the Atlantic to be ended by sunset."

As I understand it our sky will go dark and then remain dark for about twelve hours!
Either that or our sky will be cloudy and then remain cloudy for about twelve hours!
Cheers, Chris

The sky will go dark for almost 3 minutes as the shadow of the Moon races across the surface of the Earth. The sky will go dark irrespective of the clouds because the Moon is 1 day past perigee, but if there are no clouds you will be able to see the stars!

SE2024Apr08T.png
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Re: Dark Sky poll

Post by Leif »

]
Graeme wrote:
20 Jun 2022, 12:23
...as the shadow of the Moon races across the surface of the Earth.
Some lucky chap got the shadow of the ISS hurtling across his home!

International Space Station captured travelling in front of sun - BBC News
Leif.

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Re: Dark Sky poll

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Graeme wrote:
20 Jun 2022, 12:23
The sky will go dark irrespective of the clouds because the Moon is 1 day past perigee, but if there are no clouds you will be able to see the stars!
perigee meaning that there will be essentially no light from the moon at that time. New Moon.

Please and Thank You, what do the 2+2 purple ellipses represent? Something to do with the onset and offset of the eclipse, I am sure.

Only the brightest stars are generally visible where I live (The Plough, North Star, Orion) on account of all the street lights, porch lights, sensory lights and so on. I am still wrestling with my earth-centric (which is a more polite way of saying self-centred) view of planetary orbits; this may take a while.
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Re: Dark Sky poll

Post by ChrisGreaves »

Leif wrote:
20 Jun 2022, 13:34
Some lucky chap got the shadow of the ISS hurtling across his home!
Excellent post and image. :clapping: :thankyou: I have temporarily stolen the image for secure storage in my desktop-wallpaper folder.
Cheers, Chris
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