Questions tagged [telescopes]

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3
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2answers
103 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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2answers
4k views

How to Ray Trace Chief and Marginal Rays in Thin Lens Systems

Looking at the below images, the chief and marginal ray appear to be modeled just fine. But, those lines don't seem to conform to the rules typically used in thin lens ray traces. An example of ...
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1answer
16 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
53 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 ...
8
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2answers
2k views

Are there any astronomical objects at night that are dangerous to look at (through a telescope)?

Are there any astronomical bodies that would be dangerous to my vision to view through a telescope? Obviously the sun is dangerous, but are there other bodies at night I should avoid?
7
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1answer
645 views

What prevents digital interferometry in an optical telescope array?

I understand it is common to combine an array of radio telescopes in to a single instrument using interferometry. This has the photon collecting area of the combined radio telescopes but an aperture (...
1
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2answers
313 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 ...
0
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1answer
60 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 ...
7
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1answer
611 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 (...
4
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3answers
606 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 ...
4
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1answer
229 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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0answers
40 views

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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8answers
7k views

Can any telescope be used for solar observing?

Can any telescope, such as a 8" reflector, that is normally used at night to look at planets be used or adapted for solar observing? What kind of adapters or filters are required or is it better to ...
-1
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1answer
99 views

Best telescope for value per dollar? [closed]

recently I'm thinking of buying a telescope for recreational purposes. I'm looking for telescopes that have the highest performance/cost ratio, and I'm willing to spend around $200 on this. Anyone ...
5
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1answer
255 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 ...
1
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1answer
151 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 ...
0
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1answer
43 views

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 ...
1
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1answer
31 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 ...
0
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1answer
76 views

Can we use the radio telescope LOFAR to detect the FRB?

Can we use the radio telescope LOFAR to detect FRBs (Fast Radio Bursts)?
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0answers
36 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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0answers
12 views

Determine Field of View from Given Simulation Box Size

I want to determine the field of view as would be seen by a telescope corresponding to a simulation box size(comoving) of, say 100^3 Mpc^3.As I understand the box size for simulation is a rough ...
2
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2answers
83 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 ...
1
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1answer
94 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 ...
0
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1answer
64 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 ...
1
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1answer
451 views

Calculating the diameter of Jupiter through an image

I took an image of Jupiter through my 8" Dobsonian Telescope, attaching a DSLR and a 1.25" Barlow Lens where the eyepiece goes, as shown in this video: https://www.youtube.com/watch?v=reFxoF3XoaU ...
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3answers
481 views

Question about reflecting telescope

In a reflecting telescopes, light is reflected from a primary concave mirror to a secondary mirror. But the secondary mirror is never placed at the focal point of the primary mirror. Why is that? ...
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0answers
13 views

Stellar aberration: distal or local? Experimental proof?

Stokes put forward the theory (I am simplifying here.) that stellar aberration takes place out in space and that light from stars is already fixed in direction with respect to the Earth's surface by ...
1
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1answer
133 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 ...
6
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3answers
437 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 ...
0
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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 ...
1
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1answer
127 views

Non-discoveries by the Kepler space telescope: exomoons, co-orbital planets, trojans

I am just reading the review article Advances in exoplanet science from Kepler (arxiv preprint: http://arxiv.org/abs/1409.1595), and I found a remarkable paragraph (last paragraph in section "...
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1answer
40 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 ...
18
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6answers
6k views

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 ...
-2
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1answer
368 views

how does an optical telescope work? [closed]

I know that an optical telescope uses mirrors and light waves, but I still don't understand how it works. Could you please tell me? (please don't make the answer too complex or too simple.)
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1answer
68 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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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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3answers
87 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 ...
28
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3answers
6k views

Are Hubble Telescope Images in true color?

Like many others, I have marveled at the images made available from the Hubble Space Telescope over the years. But, I have always had a curiosity about the color shown in these images. An example is ...
-1
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2answers
135 views

Using wormholes to see out of the visible universe [closed]

As is commonly known, using our telescopes, we can only see so much of the universe because of its faster than light expansion. However, although under normal circumstances it is impossible to see ...
3
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3answers
4k views

Issues with Celestron 130 SLT and shaking [closed]

I have a Celestron 130 SLT reflector. I am having some issues with it and I hoped you all could help me. I'm looking for some low tech and inexpensive solutions. My telescope shakes like crazy. I ...
0
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2answers
102 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.
0
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1answer
59 views

How is the field of view of a telescope related to the diameter, D, and focal ratio, f/,of the telescope?

The question specifically relates to a Cassegrain reflector with a CCD at focus. Given the plate scale $\propto \frac{1}{f}$ and therefore $\propto\frac{1}{Df}$ with units of $\frac{arcsec}{mm}$ it ...
2
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0answers
89 views

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 \, ...
3
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1answer
90 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 ...
3
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2answers
410 views

Why isn't Zemax showing a tilt on the wavefront on my telescope design?

Attached is a Zemax file Zemax File for an afocal telescope system. When i tilt the field by an angle of 2 degrees (In green) I would expect a wavefront tilt at the "Image " plane, however when I ...
13
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4answers
12k views

Is building your own reflector telescope worth it?

I have always fancied building my own reflector telescope. I am wondering - For a certain budget, can you get better results with a home made rig? Or is this a folly, and really it would be better to ...
0
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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 ...
0
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1answer
66 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 ...
1
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1answer
49 views

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 ...
1
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3answers
3k views

Galilean telescope

I have been reading about galilean telescope and the picture in the book is something like this: After rays pass through the converging lens, there is a real image formed which is intercepted by the ...