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3
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1answer
50 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
44 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
1answer
103 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 ...
40
votes
2answers
5k 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 ...
23
votes
3answers
3k 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 ...
8
votes
1answer
263 views

Why is the Hubble Space telescope able to see farthest in the universe?

What determines how far a telescope can see in the universe? How does recording data for a very long time (~10 years) help? If we could build a telescope which work at microwave region, will it be a ...
5
votes
4answers
413 views

Is it possible to surpass the diffraction limit for telescopes?

Telescopes have angular diffraction limit depending on the observed wavelength and aperture diameter. I've read that it's possible to go beyond the limit for microscopes. But is it possible to do the ...
0
votes
1answer
27 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
71 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
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0answers
21 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
43 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
34 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
0answers
31 views

Why we see a distant object more closer from us with a telescope?

The side magnification in the image obtained by a telescope its always less than 1, then, Why we see a distant object more closer from us?
2
votes
2answers
87 views

Is it possible to build an optical system that increases the perceived surface brightness?

So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? If you increase the size of the aperture of a telescope it will ...
5
votes
1answer
57 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 ...
19
votes
2answers
5k views

What is the theoretical limit for farthest we can see back in time and distance?

13.2 billion years ago the universe was rather small, having started only half a billion years ago. Today, with the help of Hubble Space Telescope, we are able to capture the light of galaxies emitted ...
0
votes
0answers
29 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
15 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 ...
13
votes
2answers
221 views

Could a mirror array used for thermal solar power plant double as a telescope at night?

I was looking at the Ivanpah Solar facility and it occurred to me that the large array of mirrors could double as some sort of telescope array at night. The climate in the desert would be ideal for ...
2
votes
2answers
654 views

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

According to Professor Stephen Hawking, black holes emit radiation, Hawking radiation. The bigger the black hole, the fainter the radiation. That means, I personally believe, if we built large enough ...
0
votes
1answer
139 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 ...
0
votes
2answers
48 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 ...
4
votes
4answers
2k views

Are telescopes with a concave lens useful for astronomy?

Are telescopes with a concave lens (instead of convex ones) ever useful for astronomy? And if so, where are they used? Do they ever affect resolving power?
1
vote
0answers
94 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
142 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?
2
votes
4answers
818 views

How to locate the Orion Nebula?

I was trying to see Orion Nebula for few days now and I simply can't spot it. I'm using Celestron PowerSeeker 127EQ ( 5" , Newtonian , 1000m ). I'm pretty sure I have the right spot as I saw many ...
25
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 ...
1
vote
1answer
720 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 ...
1
vote
0answers
61 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 ...
1
vote
3answers
1k views

What are ADU (analog-to-digital units)?

Can someone explain simply what are ADU's? I was reading this post here: http://www.qsimaging.com/blog/understanding-gain-on-a-ccd-camera/ However, I still don't quite understand this statement: ...
0
votes
3answers
848 views

What can be seen with a 114mm Aperture 675x Zoom Telescope?

I choose to post this question on the physics exchange seeing there would be a bigger audience for answers than the astronomy exchange still in BETA. But i'm looking to buy a telescope and was ...
3
votes
0answers
107 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 ...
3
votes
5answers
16k views

Having difficulties finding objects with Celestron Telescope

I have a Celestron Astromaster 114 EQ, which I saw was highly recommended as a great beginner scope. But I just can't seem to find anything in the sky with it. Yes, I've removed the lens cap, yes I've ...
1
vote
2answers
615 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 ...
2
votes
1answer
295 views

Keplerian Telescope Exit Pupil Location - Whats the Basis for It's Formula?

For a simple two lens Keplerian telescope, this is the formula for the location of the exit pupil: $$z'=\frac{f_2}{f_1}(f_1+f_2)$$ Where $z'$ is the distance to the exit pupil location (i.e. eye ...
1
vote
1answer
100 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 ...
1
vote
1answer
57 views

Data/signal from a black hole to observe a singularity

I wonder if a situation is possible where, we measure some signal/property concerning a black hole. Supposing the measurement we make with some telescope, gets us the Fourier transform coefficients of ...
2
votes
2answers
75 views

WHY is a Refracting telescope image distance $S'=-\infty$?

In the above slide, it says that "Eyepiece '2' makes the image distance $S'$ approach $-\infty$." However, What I don't understand is that if I place my eye right at the Eyepiece 2, then I would see ...
4
votes
1answer
95 views

Absorption lines in the context of identifying elements in far away celestial objects

I understand that absorption lines are used to identify elements but how are individual absorption spectrums identified in the light that is received by a telescope?
0
votes
2answers
90 views

Can I use one convex lens to create a telescope?

Is it possible to create a telescope with only one convex lens? Specifically, is the image I drew below possible? (This was supposed to be rotated 90 degrees counterclockwise.) In this picture, ...
0
votes
1answer
159 views

Does sign convention in geometric optics fail to explain the cases of image formation by virtual objects?

Here is an example of Cassegrain telescope: Parallel rays from a distant object get reflected by the concave mirror forming an image at its focus behind the convex mirror. This image acts as a virtual ...
1
vote
0answers
57 views

Any cheap (less than 100 euro) telescope for observing Jupiter? [closed]

The moon is not challenging. I would like to observe the big planets and their rings.
5
votes
2answers
626 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?
4
votes
1answer
312 views

Future space-based telescope array

Radio-telescopes (e.g. the Very Large Array (VLA)) can simulate one gigantic dish by using separate smaller dishes. Q: Could such an array of optical telescopes potentially see an exoplanet at say 20 ...
5
votes
1answer
65 views

What do the latest FERMI results say about dark matter?

There was an announcement at a recent UCLA symposium on dark matter by the FERMI collaboration which hints at some evidence of dark matter. The results aren't yet published, but the symposium news ...
2
votes
3answers
9k views

How to ‘correct’ reflected image on my telescope?

When viewed using my reflector telescope, the image, for example the moon, is flipped over and upside down (reflected). Therefore I need to do the ‘opposite’ movements when I want to align something. ...
2
votes
2answers
237 views

How to calculate error of parallax and sextant based navigation?

First of all, why wasn't the sextant ever used for land navigation? The horizon is easier to see at sea, but land based sextants could be used in conjunction with artificial horizons (as at sea when ...
1
vote
1answer
203 views

CCD's and the photoelectric effect

Do charge coupled devices as found in telescopes use the photoelectric effect if not what eles librates the electons. Also what is charge intergration in reation to CCD's.
2
votes
0answers
55 views

need data-point: count rate of APD (avalanche photo-diode) for specific aperture and stellar magnitude

I hope lab / experimental physics is fair game for this web-site. If not, sorry! I'm designing a sensor system to perform specialized [astronomy and space-sciences] experiments, and need a "reality ...
19
votes
2answers
751 views

Optimal telescope size?

Consider a diffraction-limited telescope with unobstructed aperture $D$. Such a scope is capable of yielding an angular resolution $\alpha$ that scales as $\lambda/D$, with $\lambda$ denoting the ...