# Tag Info

31

This has been done before, so I don't have to go through all the heavy calculations using Rayleigh criterion accounting for atmospheric diffraction and visible light wavelength. Ralf Vandebergh, a Dutch astronomer, professional photographer and veteran satellite spotter has been busy trying to do exactly this since the 2007 and has indeed succeeded on ...

19

Ralf Vandebergh is one of the best amateur astronomy photographers out there who does spacecraft photography. He is using a 10" (25.4cm) Newtonian telescope, as far as I know, so this is pretty much an off the shelf telescope. He supposedly has imaged spacewalkers on previous ISS and STS missions. Though they are only a few pixels in size, and you cannot ...

15

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 tiny. So you put motors in the base of the telescope so that it slowly turns to look at the same patch of sky. You don't need to refocus because telescopes ...

13

There is one rule that is generally true for all deep sky objects (nebulae, stars, galaxies,...): Aperture matters! For solar system objects, aperture is not that important. The second most important thing is: What size are the objects you want to look at: Small objects need long focal lengths and high magnifications, large objects need short aperture for ...

12

the "mirror" cover on top of the glass had chipped away all over, giving the result of a patchy look. Optics can take a huge amount of damage (chipping, scratching) before it really starts to affect performance. You'll be surprised at the amount of abuse a telescope can take like that. As long as it's not properly cracked in two, don't lose any sleep ...

12

What else could it be? Very simply, it could all be a coincidence... What they have done is noted that objects in the outer solar system have their orbits grouped in interesting ways. Someone suggested this might indicate there was a heavy planet (or core of a giant protoplanet) that influenced their orbits in this way; the recent announcement is the ...

11

The largest optical wavelength telescope that we have now is the Keck Telscope in Hawaii which is 10 meters in diameter. The Hubble Space Telescope is only 2.4 meters in diameter. Resolving the larger lunar rover (which has a length of 3.1 meters) would require a telescope 75 meters in diameter. Information extracted from The Curious Team ...

11

All telescopes have in common that they gather and focus light from far away objects. They use a primary opical element, such as a concave mirror or a (planar- or bi-)convex lense (or lense system), and they use an eyepiece with another lense system (for viewing) or a camera in their primary focus. A refractor telescope does not sharpen the image per se. ...

11

Squinting works the same way as a pinhole camera. Ideally, light from a single point source entering your eye anywhere on your pupil will be focused on a single spot on your retina. But this works perfectly only if you have perfect vision; otherwise light entering near the top of your pupil may be directed to a slightly different spot on your retina than ...

11

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 describe your main options, and let you choose. Be aware that you'll make the choice while still not knowing much about optics. So, in a sense, it will be just the ...

11

No, the Sahara isn't a good place to build telescopes. The Atacama desert is used because it is at high altitude, which means that there is less atmosphere to get in the way. Other telescopes are located on mountaintops for the same reason. The Sahara is mostly at sea level. It's also very hot, so you get lots of turbulence due to rising air, which distorts ...

10

First you are talking about pointing the telescope at the source not focusing it on the source. Telescopes are generally focused at infinity, and there is no need to compensate for the Earth's rotation in the focusing. The speed of motion of the telescopes location on the Earth is also not directly relevant, what is relevant is the apparent rotation of the ...

10

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 reflecting photons onto every part of the CCD at the same time. You've just created an expensive, sensitive, ambient light meter. There would be no image ...

9

It depends on what you plan on using it for. For dimmer, deep sky objects you should be concerned with the balance of aperture and focal length (with a focus on aperture for light gathering power). For brighter objects, like the Moon or the solar system planets you probably don't need much light gathering power (aperture) so a long focal length for imaging ...

9

The real reasoning has nothing to do with some civilization "deliberately" hiding its radio emissions. Rather, the problem is that we can not expect some other civilization to do something we would not do ourselves. It makes no sense whatsoever to radiate large amounts of energy into space when there exist other, more economical alternatives. Radio ...

9

Yes, it would be possible. There are two roads here: Visible light In case of detecting light in the range of visible wavelength, perhaps you would consider that rare occasion when there is a solar eclipse. And it may also be possible at times of 'early' dawn and 'late' dusk. Invisible light (outside visible range, beyond the IR and the UV) Now, other ...

8

Observing the Sun through a telescope is very dangerous, whatever the telescope you use, if you don't use the appropriate tools. A telescope a basically a light collector: its purpose is to collect all the light that is arriving on his primary mirror and focus it on a point. You may have already tried to make the Sun light converge through a little ...

8

To answer the question reworded as: "What limits the quality of telescopes currently?" The answer is mostly: money. It used to be: atmosphere. But with advances in adaptive optics, ground-based telescopes are achieving what used to require a space telescope. Plus, we have the technology for space telescopes if we want, like the pending JWST. So pretty ...

7

You're experiencing a few issues all of which have one solution. Take the Scope outside. Let it acclimate to the ambient air tempurature, and then try looking. The 1st issue is the mirror needs to be the same temp as the air you're observing in. Since you are indoors you have a very warm optical path this causes distortion and trouble focusing. 2: Because ...

7

Telescopes tend to have a fixed focal length. What changes is the size of the sensor in the instrument used. If a small sensor is used, then a smaller section of the field of view is exposed, resulting in a narrower field of view being imaged than the equipment is capable of. If a larger sensor is used, more of the field of view of the telescope is utilised. ...

7

It's complicated. Until late-20th century, we've tried to make bigger and bigger monolithic telescopes. That worked pretty well up to the 5 meter parabolic mirror on Mount Palomar in California in the 1940s. It kind of worked, but just barely, for the 6 meter mirror on Caucasus in Russia in the 1970s. It did work, but that was a major achievement, for the ...

7

It all comes down to the brightness of objects (not their size). For all intents and purposes we can assume that the most distant galaxies and the small, but much closer, objects in the Oort clouds are unresolved point sources.The Oort cloud objects are too faint to see, with JWST, but it should be able to see bright galaxies and quasars even at 13 billion ...

6

Comparing telescopes that observe the visible spectrum to the radio spectrum, radio astronomers have been able to create telescopes with apertures of the order of kms, thanks to aperture synthesis. This is extremely hard in optical telescopes and the only telescope (afaik) that does so is the Large Binocular Telescope. The reason this is possible in radio ...

6

Visual resolution of a telescope is directly proportional to the aperture of the telescope. The focal length, and hence the magnification that can be achieved, is then just following on the visual resolution. The telescopes today are usually so well build that they are diffraction limited, which means optical resolution due to diffraction is the limiting ...

6

This would be the SETI's Colossus telescope project, that aims to build a high-resolution, multiple-mirror instrument with ability to directly image the heat generated by other civilizations on planets orbiting stars near us:          Artist's impression of the proposed SETI's Colossus Telescope (Credit: Innovative ...

6

Actually, one of the first confirmation of GR, is by Sir A. Eddington et al., who measured the deviation of light trays of an unsaid-as-far-as-i-know stars, on May 29, 1919. Here is an original snapshot from their experiment: They took advantage of a solar eclipse to measure the light bending from the expected position of the sources. The experiment has ...

6

Use an orrery that will let you specify a specific epoch and vantage point. There are some quite fancy ones online, for example this Solar System Scope: What you do in this particular tool is click on the calendar bar below and enter date and time of your observation (if you forgot that, there's a good chance your photograph has a time stamp, either of ...

6

They're not different. Same principles do apply. You could have secondary, tertiary, quaternary, and so on, mirrors with instruments at any wavelength, either optical, or radio, or infrared, etc. You could also have instrumentation placed directly in prime focus (so no mirrors other than the primary) with any kind of instrument - radio or infrared or visible ...

6

OK, Imagine the stars at distance x block an area of the sky. At a distance of 2x there should be four times as many stars, but they would seem four times smaller in terms of area covered. Thus, the blocking grows linearly until a significant part of the sky is blocked. The stars within 20 light years (excluding the Sun), blocks approximately $4.3 \cdot ... 6 I guess it depends what you mean by an optical telescope. However, if you just mean any telescope that can record images at visible light wavelengths, then it is possible to use these (with the appropriately cooled instruments) to make observation at so-called mid-infrared wavelengths of$\sim 20\mu\$m. See for example on the Gemini telescopes ...

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