# Tag Info

## Hot answers tagged light-pollution

63

It's a problem because there are still lots and lots and lots of ground-based telescopes. Ground-based telescopes are still (by far) the biggest optical telescopes, and the cost of space telescopes is prohibitive for many research projects. It will be a long time before a telescope anywhere close in size to the VLT can be launched. Most space telescopes are ...

34

When you look towards the horizon you are looking through a much greater thickness of air. The air does absorb some light. Dense air near surface absorbs more, and if you look towards the horizon you are looking thought a great distance of dense air. It is not "pollution" per se, though atmospheric aerosols and smoke can exacerbate the effect. ...

26

Yes, but not in the exact way you think of. To avoid light pollution it is better to go sideways. If you are in a light-polluted city, there would still be light pollution at an altitude of 400ft (the maximum operating altitude of drones) And, moreover, amateur drones are not powerful enough to carry a telescope of any useful size. So you will find that ...

16

Satellites just add moving lights to the sky, they do not obscure stars. However, some may find that disrupting their view of what a sky should look like. The visual magnitude of starlink satellites is about 5.92 at zenith, and usually darker (but also sometimes brighter). The new darker satellites are about 0.77 magnitudes fainter. This is in the lower ...

15

To expand on the "space telescopes are expensive" aspect: Space telescopes cannot be maintained or repaired. This applies not just to things like optics and instruments, but also to space-specific equipment like gyroscopes and thrusters (the James Webb Space Telescope has an estimated lifetime of $\sim 10$ years, set by the supply of fuel for the ...

11

Since Andromeda is already visible to the naked eye, to a civilization located at half the distance from the Milky Way, Andromeda would be still be visible. Its total brightness would be four times higher, but since its area would grow by the same factor, its surface brightness would stay constant. The Milky is less bright by a factor of ~2.5, but also ...

11

A nightmare for star hopping I can only speak as an amateur astronomer with a 10-inch Dobsonian. My telescope has no GOTO or tracking, so if I want to find something interesting in the sky, I have to use star hopping: taking bright stars (up to ~mag 5) as reference points, I point the finder in the approximate direction. through the finder, I can see dimmer ...

9

Planets, if any in that star system, would be visible to the naked eye, the way you can see Mercury, Venus, Mars, Jupiter, Saturn and Uranus in our system. On a virtually empty sky, they would draw that much more attention. Of course, if you had a Moon (or several moons), that would be visible too. Very rarely and briefly, asteroids passing by very close ...

8

The question is not altogether well defined. One needs to specify what wavelength is being considered and at what position in the sky - since a twilight sky has a very significant gradient of sky brightness. A paper by Patat et al. (2006) gives the brightness of the sky in the UBVRI photometric bands, at zenith, with the Sun at a variety of altitudes (...

7

One thing I always like to add is that ground based telescopes benefit from being able to take huge amounts of data. The Vera Rubin Observatory will have a 3.5 Gigapixel camera. There are proposals to sometimes run it in a mode with 1 second exposures. So we're talking data rates of gigabytes per second. If you have dedicated fiber lines you can deal with ...

6

You can see the Andromeda galaxy with a naked eye, even with some level of light pollution. So if the star you are asking about would be even closer to Andromeda, you would see at least that galaxy. There are some other galaxies that can be seen from Earth with a naked eye or with binoculars, so sky of such a lonely planet would still have some night lights ...

6

Ok go on Stellarium then hover over the left side of the screen afterwards click on the location and select London, England (City Of London is the original walled city), then go and hover over the left side of the screen and select sky and viewing options and in the sky section and select the air pollution level from location database then it will ...

6

There's a recent study on this, based on satellite and ground observations around the world. According to the paper: The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans. And there's a map: The New World Atlas of Artificial Sky Brightness. This is probably the most accurate and up to ...

6

Googling for 'light pollution map' gives a pretty good looking result. Those things usually are created using satellite measurments that are susceptible to scattered light (by measuring the polarity of light) in order to separate direct illumination from actual light pollution. I also suggest you visit a city and then compare the light pollution index on ...

6

As you probably know, the moon only shines by reflected sunlight and has a very low albedo. Its light is therefore only a tiny fraction of the light of the sun Even the light of the full moon varies, because the moon's slightly elliptical orbit brings it closer to the Earth at perigee than at apogee. Sunlight would light up the sky to about the same extent ...

5

It is pretty obvious from a dark sky. Sky and Telescope have a simulation (using stellarium) of the sky with a limiting magnitude of 6.5 (about the limit with excellent eyesight and a very dark sky). The Milky Way is very clear. Light and dark tracks are visible. It is clearly something that every person would know about and be able to see nightly. It is no ...

5

Light pollution occurs because light from the ground refects off atoms in the atmosphere. So you can reduce light pollution either by getting away from light, or getting above the atmosphere. 50% of the atmosphere lies below 5500m, if you can get 5500 m high, you half light pollution. Getting high also improves clarity, and reduces the disturbance caused ...

5

There is hope! You may be able to see some stars through a telescope even though you can't see them with your eye. For extended objects like sky brightness, nebulae, and the Moon and resolved planets, magnification reduces sky brightness, while aperture increases it. For unresolved (point-like) objects like stars and unresolved planets, as long as focus is ...

5

While light pollution certainly makes things more challenging, there are a number of objects that tend to compete with light pollution well-enough to be enjoyed. I have done astronomy outreach events from urban parks (located in downtown metropolitan areas) where light pollution is extreme. Faint deep-sky objects typically can't be viewed without special ...

5

Your problems with shielding your eyes from light probably come because it is easy to shield them from direct light from the car lights, but hard to shield them from reflected car light coming from every angle. I suggest that you experiment with closeing your eyelids while shining lights at your face. I just tried shutting my eyes while looking at a light ...

5

Space telescope Astronomy research published in Science and Nature: Ground-based telescopes (31.1%), spacecrafts (27.0%), space telescopes (22.8%). (ref) Number of professional telescopes affected: >1050. (ref) representing tens of thousands of academic physicists, cosmologists, astronomers and other scientists. Number of amateur astronomers affected: 200,...

5

"Above the light pollution" is really high and the stratosphere is a good starting point, because most of the atmospheric light scattering happens in the troposphere. Quite a few technical and regulatory obstacles here. On the other hand, directional instability (down to motor vibration) and astrophotography don't really play well. You need to ...

4

I would recommend the PiNoir Camera. Since it has no IR-filter attached, it's perfectly made for nightly observations. If you need the Raspberry just to calculate Skyglow in general, you could try to collect all light and bundle it to a beam, then measure its intensity. What also came to mind is: When calculating the rating of the night, or a point in the ...

4

Tought to answer, because the amount of airborne dust due to meteor showers and its stability in the upper atmosphere will vary significantly enough. We had many meteor showers, Perseids included, in the past that were a bit of a letdown and didn't produce as many shooting stars as initially predicted, and also the other way around of course. But here's the ...

4

Noctilucent clouds are not a problem for space telescopes because their orbits are always more than 85 km. The Hubble Telescope orbits at about 570 km. Noctilucent clouds are a problem for ground-based telescopes (although only at high latitude sites,> 50$^{\circ}$), especially if you are trying to get accurate photometric brightnesses. However, typically ...

4

It's a little hard to guess what research can be done there -- Today, Greenwich is close to the worst place on Earth to have an observatory: At sea level, in the light dome of one of the largest cities in the world, in a country famous for its clouds and fogs. The Wikipedia article on the observatory mentions the new telescope and says: In 2018 the Annie ...

4

Sky-glow is a generic term for the diffuse light not due to the sun, moon or stars (or aurorae, I suppose). Much of it is light pollution from the ground, some is the zodiacal light from dust in space, and the coolest part may arguably be the air-glow from chemical reactions in the upper atmosphere. So, depending on height the different components would ...

4

Your calculated estimate may be about correct for the limiting magnitude of stars, but lots of what you might want to see through a telescope consists of extended objects-- galaxies, nebulae, and unresolved clusters. The magnitude estimates of these objects tend to consider them as point sources, but as extended objects they have much less of a contrast ...

3

Assuming you mean Bortle class 4, then the Andromeda galaxy (M31) should be a fairly easy object with the naked eye. It won’t be particularly impressive, but rather will look like a hazy blob. On the other hand it is more than 2 million light years distant, so it’s impressive to be able to see it at all.

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