72 votes
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Why are we building larger land-based telescopes instead of launching larger ones into space?

It's cheaper. (1) With adaptive optics you can get 0.1 arc second resolution on the ground (admittedly only on a mountain top with particularly good air flow, but still!). This eliminates one of the ...
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  • 7,380
63 votes

Why is Starlink polluting the night sky a big concern if we have space telescopes?

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 ...
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54 votes
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Is it possible to mount a telescope on a plane? Is it beneficial?

This has been done. SOFIA is an infrared observatory built into a Boeing 747 SP: SOFIA takes advantage of the fact that some infrared bands are visible at atltitude, these are attenuated by water in ...
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  • 2,956
45 votes
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Why do small mirror imperfections matter with modern computers

correct for the distortion An imperfect mirror does not produce a distorted image - it produces a blurry image. With light-field sensors and phase imaging, one could possibly correct for the blur, ...
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  • 986
42 votes
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How much magnification is needed to see the planets of solar system?

You're probably asking the wrong question - which I am going to answer anyway, and after that I am going to answer the question you should have asked instead. As a general rule, there isn't much ...
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39 votes
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What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

No, it would not be a problem. Supernovae are not at all like flashbulbs – they brighten over a period of many days and dim again even more slowly. Here are a number of different light curves taken ...
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  • 7,380
38 votes

Please check my Mars photo

(Much of this echoes what antlersoft says in their answer) For a phone photo through the eyepiece that looks about right to me! The size... the brightness... both are as I expect. What you could try ...
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  • 1,488
37 votes

Shouldn't this cause a fire?

It could start a fire if the screen is at the focal point of the optical system. That is how you light fires with a magnifying glass. Here, the blackboard is likely away from the focal point, so you ...
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36 votes
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What will succeed the Arecibo Observatory?

There's no simple answer. In the immediate future, different radio telescopes around the world will pick up the slack in various ways; how that happens will depend on the needs of individual observers ...
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35 votes
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Shouldn't this cause a fire?

For a magnifying lens or mirror to be able to ignite something with light from the Sun, its surface area must be large relative to the square of the focal length. Solar energy will be spread ...
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  • 466
35 votes
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Why do satellites appear as streaks in telescope images?

Satellites are moving. They are in orbit around the Earth. Satellites in low Earth orbit are moving at about 7000 m/s relative to the ground. You can work out the orbital speed by $$v=\sqrt{\frac{GM}{...
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34 votes
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What detail can Hubble see on Mars?

Forget about magnification. People who know telescopes don't think in terms of magnification. What matters is the angular resolution, or the resolving power: the angular size of the smallest details ...
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34 votes
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Is it possible to do planet observation during the day?

Jupiter can be seen during the day. This image is by Philip Crude. Philip is an experienced astro-photographer. On his webpage http://www.billionplanetsquest.com/p/planets.html he gives details of ...
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34 votes

What should I look for in a first telescope for a child?

A desire to see “the planets” is admirable but not realistic. An affordable back yard telescope will turn planets into shaky white blobs, not Hubble images. The resulting disappointment acts as an ...
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  • 685
29 votes

Why do satellites appear as streaks in telescope images?

Can you explain me in simple words why the satellite in this telescope image appears as a streak? The exposure time is 1 second. This drawing should explain it: (Note: It could be the other way ...
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28 votes

Why can't we build a huge stationary optical telescope inside a depression similar to the FAST?

The surfaces of telescopes need to be configured to a fraction of a wavelength. If one is working in the FAST wavelength range of 10 cm to metres, then that is a relatively straightforward engineering ...
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  • 114k
26 votes

Why do small mirror imperfections matter with modern computers

Also see answers to Could mirrors be replaced with CCDs? Is Digital Adaptive Optics Possible? The problem is that light imaging detectors convert amplitude to power during the detection process. ...
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26 votes

Telescope on drones to escape light pollution?

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 (...
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25 votes

What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

If you insist on observing the exploding Betelgeuse at peak brightness, you could potentially damage your eye. The complete answer enters the realm of physiology. Here I'll discuss the astronomical ...
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24 votes
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Why different specifications for telescopes and binoculars?

With a binocular, all its optical components are fixed - the user can't change them. What's important for the user to know is the size of the front lens, which determines the brightness (and in ...
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  • 4,065
23 votes
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Could we parallax measure stars just based on the Earth's size?

In principle, it's not impossible. The Gaia spacecraft, designed primarily for measuring stellar positions, is able to measure parallaxes up to 10 kpc away with 20% uncertainty. Its baseline is 2 AU; ...
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20 votes
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A good telescope for the viewing of Nebulae, Stars and Planets

This is a very common question, yet very hard to answer if you prefer a clear, concise, uncontroversial answer that applies to all situations. So I'm not going to do that. Instead, I'm going to ...
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20 votes

Please check my Mars photo

It's very difficult to get any kind of picture just holding your phone up to the eyepiece, and the picture you posted is overexposed and probably motion-smeared, but other than that it's what you'd ...
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  • 2,661
19 votes

Will JWST be as durable as the hubble telescope?

Hubble was in low earth orbit, and was always intended to be serviceable. In fact, the original plan for Hubble was to have the space shuttle carry it down from orbit and take it back up, but they ...
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  • 2,846
19 votes
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Can large scientific telescopes observe the Moon without being damaged?

No chance of damage (the giantness of the telescope makes little difference!), but these cameras can not shoot at a shutter speed of 1/1000 second, so the lit part of the Moon is out of reach due to ...
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  • 31.4k
17 votes

Could mirrors be replaced with CCDs?

The CCD has no way of recording the direction, the point in the sky, from which a photon is coming. Say you point your mirror-less telescope at the Moon. Every point on the moon's surface would be ...
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  • 991
17 votes

Why are we building larger land-based telescopes instead of launching larger ones into space?

In addition to Mark's great answer ... Why are we building larger land-based telescopes instead of launching larger ones into space? If you had money for two homes, one near work and a 'summer ...
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  • 2,532
17 votes

Jupiter with a mobile phone and Celestron Astro FI 102mm Maksutov

Congratulations on your purchase. The first pictures dont' show anything much. Just a out-of-focus blur. The last one shows Jupiter and three of its moons. I've overlaid the image onto a simulated ...
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  • 87.7k
16 votes

How can we focus radio telescopes on a star when the earth is spinning?

Part of the answer that I suspect the original questioner needs is that although the Earth is indeed spinning very fast, the amount the surface of the Earth moves relative to an astronomical object is ...
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16 votes

Why are wavelengths shorter than visible light neglected by new telescopes?

There are some technological issues to solve with putting any large telescope into space - and a space telescope is required at UV wavelengths. It is not possible to optimise such an instrument to ...
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