Questions tagged [telescopes]

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Why are radio telescopes in orbit radio telescopes?

We use radio telescopes on Earth because of the atmosphere, right? It blocks the more energetic wavelengths but not radio waves and microwaves. So, since radiation like x-ray and gamma radiation are ...
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The Event Horizon Telescope collaboration will announce groundbreaking observations of our galaxy at 12 May 2022, what this announcement could be? [closed]

"Live webcasting for the ESO-hosted EHT 2022 event On 12 May 2022 at 15:00 CEST, the European Southern Observatory (ESO) will host a press conference on groundbreaking new Milky Way results from ...
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How could Webb's lifetime be extended? [migrated]

This article says why the lifetime of the Webb telescope is limited by the fuel it carries. Why NASA’s James Webb Space Telescope Will Never Live As Long As Hubble In short, Webb must stay near the ...
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Calculating magnification of a put together telescope

My objective lens has focal length of 50 cm and I am using a 10x eyepiece (I don't have anymore info). I am not sure how to calcuate the focal length of eyepiece. How do I find the total magnification ...
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2 votes
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How does the James Webb Space Telescope avoid stick/slip and creep problems when positioning its mirrors?

The JWST is now positioning its mirrors so they form a single image. How James Webb's Mirrors MUST Work To do this, each mirror must be positioned in 8 nanometer steps in 6 degrees of freedom. Here is ...
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Are there Wolter telescope lenses for consumer cameras?

Wolter telescopes are used for x-ray astronomy. However, I see no reason why they couldn't be used for visible light as well. How would a visible image look when taken through a Wolter telescope? Are ...
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How many pixels could an image of Proxima b taken by James Webb have?

I know it's very difficult for the James Webb to image Proxima b without a coronograph (I have been told by NASA scientists that they don't know yet whether they will be able to do so), but I wonder ...
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Doubt regarding the positioning of starshade in new world's mission of Nasa

The new worlds mission of NASA has an occulter with the telescope, Why did they place the occulter at a distance instead of attaching it to the telescope such that there is a hole as big as the size ...
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1 vote
1 answer
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Why do we see dark black spots in night sky with the naked eye if those same spots are filled with stars when looked at with a telescope?

When looking in the sky with the naked eye, we often see dark regions with no stars. However, when we look at those same spots with a telescope, it is full of stars or clouds of dust. Why is that?
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2 votes
1 answer
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Has Rindler horizon already been tested experimentally?

For an accelerated frame, there is a Rindler horizon at a distance of $$X = \frac{c^2}{a}$$ where $a$ is the proper acceleration. For $a = g$ it is about 1 light year. If one of that spacial ...
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2 votes
2 answers
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Will the spacing between the mirror segments of the Webb space telescope degrade the sharpness of its images?

I've noticed that the existing spacing between the 18 mirror segments of the Webb space telescope are many times the operational infrared spectrum wavelengths (i.e. 0.6-28μm) of the telescope meaning ...
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Why is the JWST orbit only taking 30 days?

Presumably the Ariane 5 rocket launched the James Webb Space Telescope into an elliptical orbit with its apogee at the L2 point. Such an orbit’s period is about 70 days, i.e. the journey to L2 should ...
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How can the limited to infrared James Webb space telescope do spectroscopy of the exoplanets' atmosphere without seeing in the visible spectrum?

image source: https://www.youtube.com/watch?v=bI-JIAmiL7A JWST will look for the composition of exoplanets' atmosphere using the spectroscopy method. However as far as I know for elements of the ...
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4 answers
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Why do we need very large stationary telescopes in addition to the orbital telescopes?

Most of the existing telescopes are located on Earth since it is easier and cheaper to construct, build and operate on Earth. Space launches are very expensive, and, moreover, if there is some problem ...
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Is it the term "telescope" the same as a "detector"?

For example, in this reference, MITO: muon telescope they use the term telescope but clearly the "telescope" is a muon detection system. And they also talk about angular resolution, angular ...
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Galilean telescope magnification coefficient?

So I've seen the magnification coefficient of the compound concave telescope to be $\frac{f_0}{f_e}$, but what is the magnification coefficient in the case of the convex galilean telescope? This may ...
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5 answers
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Why does magnification work?

I have read the question How do telescopes work as magnifiers? but it doesn't quite address, as far as I can tell, my question. I'm trying to wrap my head around why magnification works rather than ...
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1 answer
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Can we use meniscus lens for objective in a telescope?

I am making a telescope, but I had meniscus lens of power +1 (so focal length 1 Metre). I brought it in a optic store since I cannot find the lens of my need in any shop in my city. When I put it in ...
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1 answer
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Possible to communicate visual messages over long distances using telescopes and mirrors? [closed]

A thought experiment question: From both a theoretical and engineering standpoint, would it be possible to transmit visual messages over long distances on the surface of the Earth via a series of ...
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How to measure the size of sun projection at a certain distance from a telescope?

I was taught that light passing through a telescope, through the objective lens then passing through the eyepiece will be parallel. However, if we look at the practice, for example, making a ...
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What would be the challenges of my new telescope idea? [closed]

I have an idea of using a black hole as a new design of a telescope by placing lenses in orbit around it. Since light bends around a black hole, it should be possible for us to place lenses in a coil ...
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2 answers
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What is $\varepsilon$ in black body curve formula?

I'm currently trying to see the intensity vs wavelength curve for different temperatures using this graphing simulator. However, apart from the temperature and range parameters, there is an epsilon ...
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3 votes
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View Earth's history through a telescope aimed at a black hole

If I'm correct in saying that some of the light that left Earth in the past will have reached a black hole event horizon (EH) and that granted, some of the light will enter the EH, but that there will ...
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1 answer
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Why are the lenses of a Keplerian Telescope positioned the sum of their focal points apart?

I am currently designing an extremely simple Keplerian telescope and am confused as to why many explanations say that the objective lens and eyepiece lens are positioned a distance of the sum of their ...
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1 answer
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How should the 4 lenses in this binocular eyepiece be mounted?

I have an old 8x25 compact binocular of the make StarLux. I disassembled it for cleaning, but unfortunately the lenses in the ocular (eyepiece) sort of dropped out of the tube before I had a chance to ...
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Does the size of CCD/CMOS of a telescope affects the magnification?

For a normal, traditional telescope, the magnification level should equal to focal length divided by eyepiece diameter, i.e., $$Res=\frac{f}{D}$$ So does the size of the CCD/CMOS the same as eyepiece ...
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What's the difference between "optical amplification" and "magnifying"?

Optical amplification used widely in astronomical observatories and "magnifying" used in microscopes. What's the difference between "optical amplification" and "magnifying&...
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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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1 answer
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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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1 vote
1 answer
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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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2 votes
1 answer
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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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2 answers
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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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2 answers
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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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2 answers
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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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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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What makes diffraction spikes move with the focus?

This is a bit of a follow up on The Bahtinov focusing mask and it came with this question on Astronomy. But I think the effect can also be observed when looking through a hazy atmosphere or a stained ...
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2 votes
0 answers
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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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2 answers
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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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2 answers
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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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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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