Questions tagged [telescopes]

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Looking at Proxima Centauri b using huge telescope [closed]

I hope I didn't miss someone answering something similar. I was doing a small thought experiment. And I was wondering whether you kind people would check up on my math. Say we want to build a ...
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4answers
3k views

How does a telescope make an image larger by shrinking it?

I saw these images of how a telescope works and it seems like it is shrinking the image down to the size of the eye. I don’t understand how that makes the image bigger. My thinking is that shrinking ...
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Probability that the Hubble space telescope hit by Meteoroids

What if Hubble Space Telescope or International Space State hit by micrometeoroid or meteoroid? Asking because these objects are moving at a very high velocity.
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1answer
52 views

Why are the magnifying powers of microscopes & telescopes defined in terms of ratio of angles & not in terms of ratio of sizes of objects & images?

The magnifying power of microscopes and telescopes is defined as follows: $$m=\frac{\color{red}{\text{Angle}} \text{ subtended by the final image on the eye}}{\color{red}{\text{Angle}} \text{ ...
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2answers
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On the derivation of the north-south aberration angle

In A.P. French's Special relativity, page $39$, the author said the north-south aberration angle $\alpha$ below, in figure (b), is equal to $v\sin(\theta_{0})/{c}$, where $\theta_{0}$ is the angle ...
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1answer
189 views

How does a diverging lens in a Galilean telescope form an image at infinity when its object is at its focal plane?

This is a follow up question to Farcher's answer for the question - How does a Galilean telescope form an enlarged image even though it has a diverging lens?. Let us consider the following ray ...
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1answer
160 views

Can we use a telescope as a microscope and vice versa? [duplicate]

I got this question after I leant about microscopes and telescopes from my textbook. In a simplified compound microscope, the objective has a smaller aperture and a smaller focal length compared to ...
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33 views

How far can we look into space?

Ho distant can we look into space by using a telescope? With "telescope" I mean here any device able to detect photons of any wavelength. In terms of distance, is it correct to sat that observing the ...
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2answers
74 views

How do telescopes work as magnifiers?

I'm searching a long time for an answer without helpful results. Here are some examples of unhelpful answers: The lenses bend the light in such a way that they appear bigger — that's not an answer at ...
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1answer
31 views

Why is electric field Fourier transformed to produce image in radio astronomy?

In radio interferometry, to get an image, the correlation of electric field observed in different antennas are Fourier transformed. This gives the "brightness function in sky coordinates". Why do we ...
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17 views

Will it be possible to remotely determine the vertical temperature/pressure profile of an extrasolar atmosphere?

I was wondering why this equation seemed to work, but I guess no one has a good explanation so it is assumed to be a coincidence for now. Unfortunately, it could only be expected to work for "earth-...
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28 views

Why dont radio waves diffract through radio telescopes instead of being reflected? [duplicate]

If you take this picture of a telescope It has several gaps through it. My lecturer was mentioning how as long as the holes and imperfections in your disk are less than the wavelength of light you ...
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2answers
116 views

Why don't (can't) astronomers take advantage of interferometry to the extreme?

Reading and watching from various sources (e.g: APOD, ESO videos, or Wiki), whenever interferometry is mentioned, it is also usually explained like this: An astronomical interferometer consists of ...
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1answer
30 views

Spectrograph difference between cross disperses and echelle gratings?

In echelle spectrographs, the presence of echelle gratings and cross-dispersers is common. What task does each one perform? Why are the cross-dispersers needed?
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3answers
96 views

Do waves of light overlap?

Hopefully I can phrase this question so that it can be understood and not appear to be entirely uneducated. From what I understand when light hits an object it reflects that light toward you. Let's ...
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3answers
58 views

How are images in a telescope finite rather than just a point? [duplicate]

I understand that light passed through the objective lens of the telescope produce an image that is real and inverted, and have a height which is measured as the distance between the focal point and ...
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1answer
63 views

Could a soft telescope be created?

Everyone knows of the issues the Hubble had with its primary mirror. But could a space telescope be created that used a reflective material such as Mylar or other very reflective material? Would it ...
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1answer
758 views

Reflecting Telescope Blind Spot?

Why does the secondary mirror within the body of a reflecting telescope not produce a blind spot for the viewer. Since the light rays are being reflected from the primary mirror onto the secondary (...
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3answers
693 views

Is the black hole image in false color?

The first-ever image of a black hole released this week was taken with radio telescopes, suggesting that it is a false-color image and doesn't represent what a person would see in reality, or visible ...
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0answers
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Shouldn't we also see our galaxy clusters in that ring just beyond the shadow of M87? [duplicate]

I read that the image of the shadow taken by EHT is actually all the surfaces of the event horizon of M87 which extends to 2.6 schwarchild radius but wouldn't that also meant that we can also observe ...
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1answer
275 views

Why EHT have to use Fourier transform to process the image?

I read that Fourier transform is a mathematical tool to deconstruct a wave taken from a source into basic sine and cosine waves, since visible light coming from the M87 accretion disk will be obscured ...
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1answer
260 views

Picture of Sgr A* [duplicate]

As a lot of you may know, on April 10th we'll get to see the so said "first picture of a black hole" from the EHT. I'm no expert in observational astrophysics, so my questions are: how are they taking ...
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1answer
154 views

Black hole photography

I recently read an article that said that the event horizon telescope took a picture of a black hole (Sagitarius A*) and it will be presented on the 10th of April. I was wondering how this picture is ...
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1answer
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Is it possible (either in practice or in principle) to produce images with a LIGO-type gravitational “telescope”?

I was reading an article in the newspaper today that referred to LIGO (and gravity-wave measurements in general) as "a new type of telescope". That got me thinking -- as I understand it, LIGO uses ...
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1answer
42 views

Can solar mirrors be used for amateur telescopes?

Recently I have been fascinated by astronomy and telescopes. I have a small refactor telescope, but it cannot see very far, so I was interested in buying a larger telescope. Unfortunately, I cannot ...
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39 views

Gravitational waves interference lensing

Is it possible to detect gravitational waves interference pattern in space, using a telescopes alone or a telescope coupled by gravitational lensing?
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2answers
85 views

What in optics prohibits telescopes on jets travelling at night?

What in optics prohibits telescopes on jets travelling at night? It would be a nice addition to our sky sweep to have telescopes on at least long distant night flights. Anything in optics preventing ...
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1answer
148 views

What is prime focus of a telescope

Telescope here refers to a system of two convex lenses. In one of the problems I wanted to solve, it is given that "a Barlow lens of focal length $f_{b}$ is placed at a distance $D < f_{b}$, from ...
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1answer
73 views

Can telescope have dual purpose? [duplicate]

Astronomical telescope has a small eye piece and a large objective lens. Whereas a compound microscope has a large eye piece and small objective lens. Therefore can we use astronomical telescope as ...
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1answer
238 views

Difference between Airy disk and seeing disk

In the diffraction pattern for a circular aperture, instead of just having a circle, we have a central disk and several faint rings around the circle. Does the Airy disk consist of only the central ...
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1answer
35 views

Can we set the eyepiece of a telescope not at its focal length, to get a larger magnification?

I know the magnification of a telescope is fo/fe. But this equation is based on the setting that we put the eyepiece a focal length away from the real image of the objective. Why does we form the ...
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1answer
41 views

How does TESS focus on bright nearby stars?

How does the Transiting Exoplanet Survey Satellite "focus on" bright nearby stars, in contrast to the Kepler Mission's focus on dim distant stars? I understand that the fields of view of the two ...
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2answers
402 views

Why do we use a microscope to observe newton's ring? Can short focal distance telescope be used instead?

In newtons ring experiment we place the lens setup below a microscope which is then moved vertically until the fringes can be seen. In case of Determination of Cauchy's constants, we use a ...
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6answers
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Why put a radio telescope in space instead on the Moon?

Why are we not building a space-based radio telescope? If a lunar radio telescope is hard to build, why not a space-based radio telescope? It could be an interesting tool, I presume. Thus, what could ...
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1answer
87 views

Silver telescope mirror restoration

Our physics department has recently acquired a 26 inch diameter silver telescope mirror that is quite a bit tarnished. Would attempting a light bit of polish be possible before we try to resurface ...
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3answers
110 views

Why do we need telescopes/ binoculars/ etc? [closed]

Why do we need to use magnifying objects to see things that are far from us? Why isn't the light coming from those objects enough for us to see without special aid? Is it because light loses energy on ...
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2answers
110 views

What is the orbit of SDO (solar dynamics observatory)? How does it takes images of Sun non-stop?

There is a orbital diagram given in sdo website https://sdo.gsfc.nasa.gov/ It takes images of sun 24hr.
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Magnitude of the faintest star visible to the human eye? [closed]

Hipparcus said the faintest magnitude of a star the human eye can see is 6. How can one mathematically verify this? So far: Assumptions: Human eye receives $1000 \,\mathrm{photons/(cm^2 \, ...
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3answers
471 views

How did Jocelyn Bell aim her radio telescope (phased array)?

In 1967 Jocelyn Bell discovered pulsars using the Cambridge University radio telescope - a two hectare field of posts and wires. The pulsar was found to be in the constellation Vulpecula. How did ...
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1answer
98 views

Antenna Array Radio Telescope

I've learnt that a setup of radio antennas could possibly be used as a radio telescope: "A linear array of 10 radio antennae is set up as a radio telescope to view the sky at a wavelength of λ = 21 ...
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1answer
49 views

Can someone confirm my understanding of the photo metric system?

So from my understanding there exists a photometric system in Astronomy, such that a particular letter such as I corresponds to the I band (with I meaning infrared), and corresponds with 806nm ...
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1answer
77 views

Atmospheric turbulence and telescope resolution

I have this question asking me to decided whether we can view a a crater on the moon given the turbulence in the atmosphere turns a point source into an extended source of diameter 1". We also found ...
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2answers
30 views

View of extended nebulae from HST

I studied that f-stop has a effect on brightness of an extended objects in telescope. If f-stop is high the area over which image of extended object spread is high and brightness is low. So my doubt ...
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1answer
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How did the hubble deep field took pictures of far away galaxies?

Milyway has a radius of ~27K ly. Is our galaxy like a net with large holes that the light from another galaxy could pass straight through these holes and reach us on earth ? Theoretically, is it ...
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1answer
45 views

The Final Image? [closed]

I can't understand that if these lines are parallel to each other how and where the final image would form?
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1answer
72 views

Extracting spectra of individual stellar objects

When you look through a telescope into the heavens you see an entire patch of the sky in which there are many light sources. If I attach a spectrometer, with a diffraction (or prism), to the eye ...
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9answers
6k views

Telescopes and Time: Please Explain

I'm a psychotherapist by training so go easy on me here. I would like to know, in simple terms if possible, the basic mechanics of how Hubble can see back in time. I pretty much understand, in this ...
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3answers
13k views

How big would my telescope have to be if I wanted to see the Mars rover from my backyard?

I imagine that with a big enough telescope, I would be able to zoom in and see the Mars rover in enough detail to make out the details (like the wheels, cameras, etc.). How large would the telescope ...
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1answer
66 views

Can Neutrinos be used in space telescope?

Can we use neutrinos in the modern electronic devices such as Telescopes for capturing images, which are far from current human reach?
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2answers
165 views

(Please Explain) Clarification on extraterrestrial communication with radio waves

I just want to get some clarifications regarding the transmission and receiving of a radio waves between planets as a means of communication with aliens for story building. Is it better to transmit ...

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