Questions tagged [telescopes]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
2
votes
2answers
573 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 ...
0
votes
1answer
788 views

Refraction of light In convex lenses [duplicate]

I came across this image when researching refraction in lenses. I can't understand why the light does not refract at the points which I have marked with burgundy arrows even though it is crossing a ...
0
votes
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)?
0
votes
1answer
65 views

Hypothetically giant telescope

As the James Webb telescope is getting ready for launch after years, I wonder in a purely hypothetical scenario, a telescope which is as huge as the diameter of Earth will make what kind of ...
1
vote
0answers
468 views

Problems with using Compound microscope and telescope in the place of each other

Compound microscope is used to see magnified image of tiny objects. Whereas telescope is used to see distant objects' magnified image. I wonder can we use telescope to see small objects placed close ...
0
votes
2answers
523 views

A confusion about the use of telescope

Suppose we are measuring wavelength of a light with the help of spectrometer and a grating. Spectrometer consists of three main parts: Collimator, Turntable, Telescope. Grating is placed on turn table....
0
votes
1answer
96 views

How do you prevent electromagnetic radiation emitting from a new house? [closed]

Does anyone know how to prevent electromagnetic radiation emitting from a new house? We live very near a radio telescope and we're told that electromagnetic radiation from domestic houses causes ...
1
vote
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 ...
0
votes
1answer
127 views

Heisenberg Uncertainty Principle and Telescopes

I've heard an analogy on the news regarding the Webb telescope. It said Webb's resolution is such that it would be able to locate from Earth a bumble bee on the moon. I understand that it will be a ...
5
votes
1answer
79 views

Why is the James Webb Space Telescope difficult to open?

At recent induction day I was shown around the labs at a satellite company. The academic giving the tour was talking about the James Webb telescope (they were working on testing some component that ...
1
vote
0answers
45 views

what is the telescopic retinal illuminance of a star?

What is the retinal illuminance (in trolands) or luminance (in $cd/m^2$) of a star image viewed through a telescope? I'm looking for a formula that will calculate this value for input values of star ...
0
votes
1answer
134 views

Using starlight to create a fire

It is easily experimentally demonstrated that a focussed image of the Sun can be used to start a fire. Furthermore, by thermodynamic considerations or the conservation of étendue, it can be shown that ...
1
vote
0answers
84 views

World's Largest Radio Telesope : How accurately does it need to be figured?

In Guizhou Province, China, the worlds largest radio telescope is almost complete, measuring 500 metres across. I am aware that todays largest optical telescope require very accurate figuring and ...
2
votes
2answers
99 views

Why don't reflector telescopes place their reflectors at an angle?

To avoid placing a secondary mirror in front of the objective mirror, why not tilt the objective and design the eyepiece in such a way that comatic aberration is minimized?
1
vote
1answer
452 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 ...
1
vote
1answer
215 views

What is meant by the point-source response of eye or telescope?

I have heard that a source is called unresolved if it is much smaller in angular size than the point-source response of the eye or telescope observing it. What is the meaning of point-source response ...
6
votes
5answers
1k views

What is the physical meaning of magnifying power of a telescope?

So the following question was given in the JEE Mains 2016 conducted throughout India on 3rd April. An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To ...
0
votes
1answer
453 views

How can one tell how much light is blocked by a secondary mirror in a reflecting telescope?

I've been reading about reflecting telescopes and I understand how the secondary mirror doesn't cause any obstruction to the image itself, but I've read that it does dim the image by blocking the ...
3
votes
2answers
89 views

Can we see the famous black hole pair or its effect on other stars in any other means but LIGO?

If the source of LIGO's detection is a pair of black holes, can we see them using a traditional electromagnetic/neutrino/some other kind of telescope? Or can we see their effect on other stars in ...
1
vote
0answers
116 views

Telescopes and faster than light travel [closed]

If sometime in the future we master faster than light travel, could we solve past crimes by warping to a place in space where the light from Earth is just arriving from that time period and using a ...
1
vote
0answers
69 views

Wavelength limited resolution

I've read through answers to similar questions, and I haven't been able to find a satisfying answer. I've heard it said that in order to make out something, you need to use light with a wavelength at ...
1
vote
1answer
98 views

What is the limit of the deep field exploration?

The deep field exploration is quite fascinating, first the Hubble Deep Field (HDF) showing a small piece of the Univers one billion year after the Big-Bang, next the Hubble Ultra-Deep Field (HUDF), ...
-1
votes
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 ...
2
votes
0answers
96 views

Given a focal length and an aperture of the telescope, what is its field of view?

While I know FOV of scope is equal to FOV of eyepiece divided by magnification. How can one find FOV given only the focal length and aperture of the telescope?
0
votes
0answers
336 views

Refracting telescope image formation

I'm having some trouble understanding how a refracting telescope forms a magnified image for an object that is not assumed to be infinitely far away. I drew this ray diagram: And as you can see, a ...
2
votes
2answers
334 views

How accurately could we theoretically see into far space?

Travels to different galaxies are strongly limited by the speed of light. Unless we find a way to travel through space with some wormholes, we will never reach planets in another galaxy. But what ...
3
votes
3answers
226 views

Is it possible build a telescope on a field of mirrors?

Is it possible build a telescope on a "field of mirrors" like the image below? I mean, an energy plant on day time and a telescope in the night Maybe the mirrors are not enough polished but the ...
3
votes
1answer
212 views

The James Webb Telescope, why are there 5 levels of protecting foil?

From simple curiosity, does anybody know why there are around 5 layers of solar radiation reflecting foil on the James Webb Telescope, rather than one or two? Is it to save weight, or (probably) ...
3
votes
2answers
238 views

Why array of telescope is used?

To increase the resolution of an instrument, smaller wavelength and larger aperture is desirable. It is mentioned in some textbooks that the "effective" diameter of a telescope can be increased by ...
2
votes
2answers
202 views

How can the Hubble telescope see the light from galaxies that are millions of light years distant?

The Hubble Space Telescope is in the news every now and then. How can it photograph galaxies that are millions of light years from Earth? We can understand that light comes from galaxy and Hubble "...
50
votes
2answers
7k views

Why are gold mirrors yellow?

Why are golden mirrors yellow? Do they add a yellow component to the spectrum or absorb non-yellow components? If they absorb, then why are they used in telescopes being imperfect? If they add a ...
-1
votes
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 ...
28
votes
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 ...
0
votes
1answer
389 views

Detecting molecules in space?

http://www.forbes.com/sites/alexknapp/2012/02/24/nasa-detects-solid-buckyballs-in-space/ I refer to the above article, which mentions that buckyballs "far smaller than the width of a hair" were ...
1
vote
3answers
119 views

Why do telescopes move synchronously?

Here's a very nice video (see it in HD) of timelapses captured at the atacama desert. In the beginning of the video you can see that 4 telescopes move synchronously. Could anyone explain why? I always ...
1
vote
0answers
30 views

Is there a limit to telescope resolution? [duplicate]

Could a strong enough telescope read a newspaper on a planet 1400 light years away, or is there a theoretical limit to the resolution of magnification?
1
vote
3answers
57 views

About light nature [closed]

I have some particular questions about the nature of light...cause all I know from all sources is that it is a wave and a particle and stuffs, but if light "COMES" from all directions, and is in every ...
2
votes
1answer
263 views

Is surface brightness constant as a function of distance?

Well of course it is - the flux drops off as the square of the distance, but the solid angle subtended by the source drops off the same way, so surface brightness is constant, right? Yet other ...
0
votes
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? ...
5
votes
1answer
132 views

A Difficulty with Liquid Metal Mirror Telescopes

"Another difficulty is that a liquid metal mirror can only be used in zenith telescopes" [Wiki] Why is that? Why can't a series of flat mirrors be used to reflect light coming from any angle to be ...
0
votes
0answers
143 views

Magnification: Microscopes Telescopes

What is the difference between the way a microscope magnifies say a star and a telescope say a cell? Why is it, that the eyepiece of a telescope magnifies stronger when it is smaller and with a ...
0
votes
0answers
32 views

Is image scale the same as focal length?

I am supposed to show using a diagram how image scale is related to focal length. But my formula for image scale is $$\text{image scale} = \frac{y}{\theta} = F$$ where $y$ is the image size on the ...
3
votes
2answers
731 views

Is there a way to photograph the very edge of black hole?

According to Professor Stephen Hawking, black holes emit radiations known as Hawking radiations. The bigger the black hole, the fainter the radiations. That means, I personally believe, if we built ...
0
votes
2answers
94 views

What is the maximum of information in a beam of light?

If I look at the space I can see the Andromeda Galaxy as a small dot in the sky. If I look through a telescope, I can see the spiral shape. If the saw right through a huge telescope, I could see a ...
7
votes
1answer
646 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 (...
6
votes
3answers
216 views

How big would a solar sail need to be to be detected from the orbit of Pluto?

Suppose we made a solar sail out of a highly reflective material. How big would that solar sail have to be for the Hubble Space Telescope to detect it visually at the average distance of Pluto?
1
vote
1answer
6k views

How long does it take for pictures by Hubble to arrive on Earth?

Recently, there was news that Hubble took a high definition picture of the Andromeda galaxy. I wanted to know how long does a high definition picture from Hubble takes to arrive on Earth; if at all ...
31
votes
3answers
3k views

How do we stabilise satellites so precisely?

Look at the Hubble Ultra Deep Field photo. The stars in it are on the order of 1 arcsecond across. To an order of magnitude, this is $10^{-6}$ radians in a $10\text m$ telescope which was held steady ...
0
votes
1answer
371 views

Resolving power of ultra-telescopes [duplicate]

Assuming we could create and orbit optical telescopes of arbitrary size, perhaps starting with (say) inflatables or active membrane of 100m diameter what kind of resolution in imaging extra-solar ...
1
vote
0answers
272 views

If we increase the aperture of a telescope and decrease its magnification, can it be harmful to the eyes?

The full moon is the brightest object in the night sky. I believe that if we increase the aperture of the objective, and decrease the magnification of the telescope, it might concentrate a dangerous ...