Questions tagged [telescopes]
322 questions
71
votes
3 answers
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 have to be? (or how can I calculate this value?)
Josh
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60
votes
7 answers
Why do some lights captured by the Webb telescope have rays and others don't?
On the images captured by Webb telescope one can see some lights with 6 rays, but most others don't have any. One would expect the optics to transform all light sources at infinity in the same manner. What causes these differences?
Michael
- 1,991
52
votes
2 answers
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 yellow component, then where do they take energy for…
Dims
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34
votes
6 answers
Why did high quality mirrors use aluminum coatings instead of silver?
I have two questions on mirrors.
I’ve read that in the past quality mirrors were coated with silver but that today vacuum evaporated coatings of aluminum are the accepted standard. When I look at the reflectance vs. wavelength plot,
I see that…
Carlos
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33
votes
3 answers
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 for $10^6$ seconds.
In other words, the velocity…
spraff
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29
votes
4 answers
Telescopes to avoid as a beginner?
I've heard people talk about "department store scopes" or "trash scopes". How do I know what to avoid in a beginner scope? How can I know that I'm not getting something we will be more frustrated with than excited about?
BradC
28
votes
2 answers
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 at that time.
The point at which Earth exists…
Ankur
- 381
28
votes
3 answers
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 shown below. Are the colors we see, such as the…
K7PEH
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26
votes
3 answers
How to determine what size telescope to buy
A couple of years ago my son showed an interest in astronomy and we bought a 6" reflector telescope. We use it pretty regularly and have enjoyed it immensely. Lately we've both been wishing we had something bigger to be able see more things and to…
Walter
24
votes
8 answers
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 case, that light has to travel extremely long…
Tracer
- 373
22
votes
2 answers
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 wavelength of the light. However, in reality such a…
Johannes
- 19,343
22
votes
4 answers
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 locations on Antarctica? Are there any other…
macco
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19
votes
4 answers
How does a telescope make an image larger by shrinking it?
I saw these images of how a telescope works and it seems like it is shrinking the image down to the size of the eye. I don’t understand how that makes the image bigger. My thinking is that shrinking an image makes the image obviously smaller and you…
user11937382
- 383
19
votes
5 answers
Why don't we have a better telescope than the Hubble Space Telescope?
The Hubble Space Telescope (HST) was launched in 1990, more than 20 years ago, but I know that it was supposed to be launched in 1986, 24 years ago. Since it only took 66 years from the fist plane to the first man on the Moon why don't we have a…
grassman
18
votes
5 answers
How do telescopes see many billion light years distant object in our universe?
How do telescopes see many billion light years distant object in our universe?
As an individual with limited expertise in the field of astronomy, my current understanding suggests that the observation of the furthest points in the universe using…
