Tag Info

Hot answers tagged

24

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 ...


16

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 ...


11

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 ...


10

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 ...


10

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 ...


8

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. ...


8

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 ...


8

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 ...


7

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 ...


7

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 ...


7

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 ...


6

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 ...


6

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 ...


5

M31 is actually something like 141,000 light-years in diameter (there has been some variation in our understanding of its size, but 141K is good compromise). M31 is 2.54 million light-years from us. The rotational speed of stars near the edge of the galaxy's disk is in the vicinity of 200 km/sec. Given all that, in one year a star in the vicinity of the ...


5

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 ...


5

Yes, stacking Barlow lenses is a common practice to effectively increase focal length by multiplying their individual focal lengths. When I say common, most advanced eyepieces actually have many glass elements and are a type of a Barlow lens themselves, so just by using a single Barlow lens in front of your eyepiece you'd already be, technically, stacking ...


5

It's a broad question, but I'll take a stab trying to provide the essentials for a good start. Also see this post which contains important additional information: Best telescope for the viewing of Nebulae, Stars and Planets There are many, many factors involved in choosing a telescope. You seem settled on a dobsonian. That's not the only possible choice, ...


5

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 ...


5

Jupiter is pretty easy. A little refractor with a 50 mm aperture (diameter of the primary lens) will show you the disk of Jupiter and the biggest two equatorial belts, and the four galilean satellites. Or Saturn and its rings - that's doable too. The image will be tiny, but you'll see those features - assuming the instrument is not junk and it can take a ...


5

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. ...


5

What can a lunar-based telescope do? First, you would have no atmospheric distortions to interfere with the viewing. Second, there would be no atmospheric absorption of ultraviolet or infrared light. Third, there would be no cloud cover, so viewing can be almost continuous (the sun may interfere). However, the star should be bright and its ...


4

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 ...


4

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 ...


4

Well the angular resolution of a telescope depends on two things: 1) The wavelength of light you're looking in, and 2) the diameter of the primary lens/mirror. $$ \theta = 1.22 \frac{\lambda}{D}$$ where $\lambda$ is the wavelength of light and $D$ is the diameter of the lens. Light collecting power is simply how many photons you can collect in a ...


4

Quoting the most relevant parts from the Richard McDonald's Wiki on Astrophotography Mounts: Periodic Error Correction: Periodic Error can be reduced to an acceptable level using a variety of techniques, only some of which are in the range of a beginner or mid-level astrophotographer. Throw Money at the ProblemVery high-end mounts for ...


4

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 ...


4

Amateur telescope making (ATM) is a popular past-time for astronomers. You can grind your own mirror, or you can buy ready-made mirrors. You can coat your mirrors with silver using chemical solutions yourself, or have a coating of aluminium applied using a vacuum chamber by an outfit offering such a service. The main materials are a thick round slab of ...


4

A parabola does indeed focus over a broad frequency range. The lower limit is determined by the dish diameter, the upper by the construction (mesh size, parabolic accuracy etc.). The collector placed at the focal point may be a simple dipole or other fixed frequency antenna, or more commonly, a waveguide that leads the collected signals to a low noise ...


4

There are many other variations on telescope designs others than the ones you have mentioned. They differ in the light path, the shape of the optics utilised, the use of mirrors and/or lenses, and the physical structure. A Schmidt-Cassegrain is a particular type of Cassegrain reflector. A Cassegrain reflector uses two mirrors, a primary and a secondary. ...


4

The differences are in the designs: Newtonian: Gallilean: Schmidt-Cassegrain: Schmidt-Cassegrain telescopes are characterized by including 1 convex mirror, 1 concave mirror and 1 correction plate.



Only top voted, non community-wiki answers of a minimum length are eligible