# Tag Info

## Hot answers tagged telescope

69

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 major advantages of space until you get above several meters mirror diameter. (2) Rocket fairings are the shrouds which protect payloads during the supersonic ...

52

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 the atmosphere so they're less visible on the ground. There have been infrared observatories before SOFIA: The first use of an aircraft for performing ...

43

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 ...

39

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 point in pushing the magnification above 2x the diameter of the instrument, measured in mm. 3 inch, that's 75mm, that's 150x max. Beyond that limit, even under ...

39

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 from Wikipedia: The rise is fast on an astronomical scale – several orders of magnitude over a period of roughly ten days – but very slow on a human scale. An ...

38

(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 is to use the manual mode of your phone's camera and set the ISO down to minimum (100) and the shutter speed down to something like 1/60s. Take a few shots, ...

34

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 that you could see in an instrument. Rule of thumb: the resolving power of a telescope with a diameter of 10 cm is 1 arcsecond when using visible light. The ...

34

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 can see the shape of the eclipse (and you get a bigger image) without setting things on fire. Although this is fairly safe, there are a few things to pay ...

34

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 throughout the projected image, and the size of that image will be essentially proportional to the focal length, making its area proportional to the square of focal ...

34

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 the equipment and settings used: This image was captured through my [i.e., Philip Crude's] Celestron CGEM-800 using a ZWO ASI120MC camera at prime focus. ...

33

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 and collaborations. Unless someone was to build an identical observatory at the same latitude as Arecibo, with the same frequency range, receiver options and ...

24

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 ...

24

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 parts: Betelgeuse will explode as a type II supernova, the typical brightness of which is around $M \sim -17$. With a distance of $d\simeq200\,\mathrm{pc}$, its ...

24

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 theory sharpness) of the image, the magnification, and the field of view. These are all useful things to know. A telescope has an interchangable component, namely ...

22

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; $2.3\times10^{4}$ times larger than the diameter of Earth. Thus, placing two Gaias on each side of Earth would be able to measure parallaxes of stars up to a ...

20

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 ...

20

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 expect. Planetary observation is a learned skill; planetary detail is usually very low contrast. Mars is a small target and you have to use lots of magnification,...

17

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 image from stellarium (at about 10pm BST, the moons move pretty quick so you need an exact time!): You can clearly see which moon is which, and why Europa is ...

16

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 ...

16

The disadvantages would likely outweight the advantages. It's cold out there. This makes it easier to keep an infra-red telescope cool The sun's just a super-bright star. This means more of the sky is visible and not in the glare of the sun. However you orbit so slowly that there will be a few objects that you won't be able to image because they are behind ...

16

Satellites, even in geostationary orbits, move with respect to the background stars and make "trails" on telescopic images that are tracked at the sidereal rate. Removal of these can be as straightforward as taking the median of a set of exposures. What I mean by this, is that in a sequence of exposures, the satellite trail will pollute different ...

15

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 work at both UV and IR wavelengths because of issues like cooling, mirror coatings and such-like. The simple angular resolution limit of a telescope goes \$\lambda/...

15

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 decided that was too risky compared to servicing in orbit. JWST, on the other hand, will be at the Earth/Sun L2 Lagrange point, like WMAP and Planck before it. ...

15

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 cottage' in the woods, how would you divide your budget? This question is a follow-up to Do bigger telescopes equal better results? Yes, and I'm not a fan of ...

14

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 ...

14

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 ...

14

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 ...

14

You're correct in that the sharp dropoff is simply because there are very few planned major telescopes operating in the UV range, whereas there are a substantial number planned in the infrared range. As I mentioned in my answer you linked to, CHARA and the EELT, two of the top planned infrared/visible projects, will use new adaptive optics technology, making ...

14

I'm pretty certain it is the 200inch Hale telescope at Palomar Observatory. There is an image galley of the 200 inch telescope. According to Richard Preston's book First Light: The Search For The Edge Of The Universe, Einstein attended the completion of the telescope truss, yoke and horseshoe bearing at Westinghouse Electric and Manufacturing Company in ...

14

Supplemental answer based on @JamesK's When looking at an object through Earth's atmosphere, we know that it removes some light multiplicatively due to absorption and scattering contributes some light additively due to things like scattered light from other sky objects (e.g Moon and now Sun) and skyglow. During the daytime you can dramatically improve your ...

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