Questions tagged [telescopes]

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Infrared Telescopes and Surface Area

I have been reading a paper on about exoplanets, specifically measuring the temperature of exoplanets using infrared telescopes. The paper compares exoplanets with neutron stars (NS) remarking that ...
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Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
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Ray Diagrams: Where is the eyepiece located in a reflector telescope?

I'm in the process of building my own reflector telescope; I have an 8" primary mirror with a focal length of 1200mm. Of course a telescope has a focuser that lets the eyepiece move up and down ...
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Can we make a curved mirror out of many small flat mirrors in telescopes?

Will it be possible to build a telescope using many small flat mirrors as a replacement for the prime curved telescope mirror? If the answer is yes, can you please provide a formula connecting the ...
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Can we improve x-ray telescopes by a factor of 100,000 with better image sensors?

As long as the image sensor`s pixels are smaller than the imaging system's point spread function, they don't influence it. However, if we look at the Hubbel telescope, it has an NA of 1/48, making its ...
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Can telescopes go beyond the diffraction limit by having a better image sensor?

I read the wiki article about angular resolution, but I struggle to understand the image sensors' role in telescopes. Will better image sensors can help go beyond the diffraction point? If not, how to ...
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What is the theoretical limit for image sensors

Telescopes are principaly limited by a diffraction-limit. Does this limit affect the image sensor? The Rubin Observatory LSST Camera, the biggest camera in the world with 3.2 gigapixels is having a ...
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Can an image formed by gravitational lensing be corrected for the inevitable aberration?

Carl Zeiss would not be impressed with your average gravitational lens. Compared with familar optical lenses that are generally used to form sharp undistorted images, gravitational lenses make quite a ...
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What is the magnification of the image produced by a convex objective lens in a refracting telescope

Let's say a refracting telescope with a convex objective lens and a convex eyepiece is viewing a distant object in space. Will the image produced by the convex objective lens be magnified or reduced? ...
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Plausibillity of using a black hole as a telescope?

I recently learned about the proposed FOCAL telescope, which would use the Sun's gravity as a lens to observe exoplanets (or whatever it's aimed at) with incredibly high resolution. Obviously, the Sun ...
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Is there a difference between the image captured by a big telescope and a small telescope at several points in spacetime?

Suppose we build a big reflector telescope, with its mirror being the size of a city. That telescope gathers a bunch of photons at a given instant and creates an image of Jupiter. Now, the big mirror ...
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Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
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Laser interferometry for relative movements between two mirrors

I have been struggling in the past weeks to understand how should I setup a laser interferometer for my experiment. I am not a physicist, and I am quite new to optics. I have a Cassegrain telescope ...
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Can the Event Horizon Telescope be built around the sun?

Would it be possible to build an Event Horizon Telescope around the sun by sending multiple spaceships to orbit the sun? What is the theoretical accuracy of time and place needed for each such ...
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Time and position accuracy requirements for the Event Horizon telescope

The black hole at the center of M87 imaged last year by the Event Horizon Telescope, using Very Long Baseline Interferometry, at Earth subtends an angle of about 20 microseconds of arc. This happens ...
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Primary focal length of a cassegrain telescope

How to choose the primary mirror focal length of a cassegrain telescope if your focal ratio is known.
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What is the optimal focal length of a cassegrain telescope or how is this decided?

Since the total focal length of the cassegrain system is given by: F = (f1*f2)/(f1-f2-D) Where F - total focal length f1 - focal length of primary mirror f2 - focal length of secondary mirror D - ...
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Cassegrain telescope design

How are the dimensions of a cassegrain telescope configured? In particular the distance of the secondary hyperbolic mirror from the primary mirror and also the diameter of the secondary mirror. Any ...
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What determines if light rays will be parallel to each other after refraction through a lens?

This is an example of a refracting telescope: As you can see, when passing through the eyepiece (second lens), the rays are refracted parallel to each other. Why are they refracted parallel relative ...
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Hubble mirrors shape [closed]

The Hubble mirrors are two hyperbolas. I see on Wiki the formulas for the Ritchey–Chrétien telescope. https://en.wikipedia.org/wiki/Ritchey%E2%80%93Chr%C3%A9tien_telescope My question is how is the ...
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Resolving power of telescope and circular aperture

From the formula of circular aperture we get: sinθ=1.22λ/D But according to this formula, the θ is the angle on the side of the Airy disc formed. The formula for angle of resolution for a human eye ...
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Why don't ionic liquids evaporate in a vacuum?

Proposals exist for a rotating liquid mercury telescope on the Moon, using ionic mercury. Pure mercury has a triple point at 312 K and 0.2 mPa, but the Moon's surface pressure is far lower than this. ...
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Experiment involving a homemade Michelson stellar interferometer

I am in high school and for a research essay I am thinking of writing on the topic of Radio interferometry. My school has a Newtonian telescope and I was thinking of building a Michelson stellar ...
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Is there a maximum limit on the distance beyond which we can't resolve an image using a reflector telescope in the visible light spectrum

Through Rayleigh's Criterion, it is implied that there is a maximum distance beyond which we cannot resolute an object. This limitation is due to the limitation in the size of the aperture of the ...
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Frozen liquid mirror space telescope

I saw Liquid-Mirror Telescopes. With care, a liquid mirror can make a diffraction limited telescope. The Wikipedia article on Liquid mirror space telescopes talks about various designs for use in ...
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What is the minimal equipment required to observe the Apollo lunar retroreflectors?

It's rather well known that the Apollo lunar landings installed retroreflectors on the Moon, and that these can be used to reflect laser beams back at Earth, to measure the Earth-Moon distance to ...
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Are X galaxies (PKS 2014-55) collisions?

Recent radio imaging by Meerkat of PKS2014-55 show an xshaped galaxy with a distinctive core and lobes. https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Pks+2014+meerkat&btnG=#d=...
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Limits of zooming in (for camera/telescope)

What limits the ability of a camera/telescope to zoom in on distant objects? The question is twofold: What zoom really is? Firstly, I would like to gain clear understanding of what we mean by zoom ...
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Do the size of the objective lens of a telescope affect the size of the field of view?

According to diagrams like this the answer is no, because every part of the objective lens gives the whole image. But when I cover part of the objective lens of my binocular, I only see part of what I ...
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Can we turn a single telescope into Event Horizon Telescope?

Event Horizon Telescope is a network of telescopes that sync together to focus on a distant object and act as one huge telescope. I wonder if the same effect could be achieved with a single telescope?...
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Number of photons collected by a telescope [closed]

I’m trying to calculate how many photons of frequency $1420$ Mhz are collected by a telescope of area $100$ m$^2$ per second from the Andromeda Galaxy, which is 2 million light years away and has a ...
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How can diffraction occur in a reflecting telescope?

It's understandable how diffraction occurs in refracting telescopes, because the lens itself is a small aperture for light to pass through. But what about reflecting telescopes? Since light is ...
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Why does convex lens diameter affect its magnification?

Usually , reflector telescopes will have a greater angular magnification because the focal length can be increased in the same physical distance, so to achieve the same angular magnification, ...
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Why do refracting telescopes have a wider field of view than reflecting telescopes?

Many websites say refracting telescopes have a wider field of view than reflecting telescopes, claiming it is because their angular magnification is less. Astronomical objects are therefore easier to ...
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Projecting a telescope image

Is it possible to theoretically project image of telescope without digital technology? If so, how can I do this?
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Do enough photons from Proxima b make it to Earth that its surface could be imaged directly with a huge, but not astronomically so, telescope?

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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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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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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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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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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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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106 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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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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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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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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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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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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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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