Questions tagged [telescopes]
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208
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1answer
11 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
52 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 ...
0
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1answer
58 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
590 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
597 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 ...
1
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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 ...
4
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1answer
219 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 ...
5
votes
1answer
253 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
150 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
30 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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0answers
35 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
vote
1answer
82 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
63 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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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
124 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 ...
1
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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 ...
1
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2answers
280 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 ...
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 ...
1
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1answer
66 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
84 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
100 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.
2
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0answers
85 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 \, ...
6
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3answers
433 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 ...
3
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1answer
89 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
64 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 ...
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 ...
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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?
1
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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 ...
25
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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 ...
74
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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 ...
0
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1answer
62 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
163 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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3answers
69 views
What happens after the light from the sun has travelled its entirety? [duplicate]
The light from the sun will stop traveling after a particular distance due to its intensity becoming 0.
Up to which planet does the light from the sun travel before which it dissipates into nothing?
...
3
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1answer
190 views
Number of photons required for communication
On one hand, the amount of information I can transmit is proportional to the bandwidth. The higher the frequency, the more information I can transmit. On the other hand, the number of photons is ...
0
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1answer
61 views
How can I make a Telescope with the lenses I have
List of lenses I have
Convex - 200mm F.L - 50mm Dia
Convex - 50mm F.L - 50mm Dia
Convex - 40mm F.L - 40mm Dia
Convex - 45mm F.L - 25mm Dia
Concave - 200mm F.L - 50mm Di
I tried to make a ...
0
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1answer
38 views
Optical interferometer using software
I understand that optical interferometer is a technique by which we can combine light from multiple telescopes and combine them in optical interferometer to simulate effect of larger telescope with ...
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1answer
345 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
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 ...
1
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2answers
292 views
Angular displacement, minimum diameter of crater, and telescopes
A telescope gives a clear view of a distant object when the angular displacement between the edges is at least $9.7 × 10^{-6} rad$.
The Moon is approximately $3.8 × 10^5$ km from the Earth. Estimate ...
0
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1answer
39 views
Question about my reflective telescope
So I have a Astromaster 114EQ reflective telescope my buddy has a refractor telescope a cheap one. But we were looking Jupiter through mine and it was just extremely bright without colors. But my with ...
18
votes
3answers
5k views
Why is the South Pole Telescope located exactly at the South Pole?
I read that there is less atmospheric interference for the telescope at the South Pole because the atmosphere is thin and there is less water vapor in the air. However this seems to be true for many ...
3
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1answer
114 views
Is interplanetary (or larger) very long baseline interferometry (VLBI) possible at any λ?
Assuming that it's possible to get the equipment (including accurate clocks) there in the first place, and that it's possible to get the data back afterwards, is it possible to do very long baseline ...
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2answers
85 views
Why would one paint the framework of a telescope red in the tropics? [closed]
[Full question below]
If it's painted red it will reflect red/absorb bluer light. Don't see how this makes any difference to the telescope. Because the tropics are mentioned I assume that the sun ...
2
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2answers
554 views
Is a mirror-less telescope possible?
I was reading about telescopes and the Hubble Telescope for example has a 2.4m mirror which reflects lights to a sensor. Other type of telescopes use lenses to focus light to the imaging sensor.
I ...
