Tagged Questions
4
votes
0answers
47 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 ...
9
votes
0answers
145 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 ...
2
votes
1answer
94 views
Why do focal lengths affect magnification?
For compound lenses, the image formed by first lens acts as the imaginaryobject for the second lens.
In telescopes, the objective lens projects an image on its focal point which works as the object ...
6
votes
2answers
142 views
Why does a blue sky at dusk appear nearly black through a telescope?
Earlier this evening I was looking at the Moon through my cheap toy telescope (x150 magnification) when I noticed a (rather mundane) optical effect I couldn't explain. The Sun had just dipped below ...
2
votes
0answers
130 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 ...
0
votes
0answers
45 views
Observing through a 90 degrees positioned telescope on a flat surface
Assuming I'm standing in the middle of the ocean with a large telescope, positioned such that it's angle is 90 degrees (i.e, it's parallel to the sea) and assume that there are no light interferences ...
2
votes
2answers
171 views
Why do we stop using optics for photons above a certain energy?
I'm reading about how the soon-to-be-launched NuSTAR is on the cutting edge of focusing x-rays, which captures 5 to 80 keV radiation by focusing them with optics that have a 10.15 meter focal length ...
3
votes
2answers
67 views
Adaptive Optics Capability in the Visible Range
Telescopes with adaptive optics (AO) have been in use for several decades. To my knowledge, the lowest wavelengths utilized are in the near-infrared. It's known that Fried parameters are smaller for ...
4
votes
2answers
146 views
How to adjust feather touch focuser for collimation?
I have a Starlight Instruments feather touch focuser for my Dobsonian telescope.
While trying to collimate the secondary mirror with the focus all the way in, I noticed that my Howie Glatter laser ...
3
votes
2answers
310 views
Hartmann mask based collimation
Is there a detailed description for a Hartmann mask based collimation process?
I've been told by a friend that is possible to collimate an SCT by placing a three round holes Hartmann mask at the ...
3
votes
3answers
47 views
Quality loss when adding more components to a telescope?
I would think this would be inherently true, but I'm curious:
(Assuming the highest quality amateur instruments are used.)
Is quality lost when, say, adding a T-mount adapter, diagonal or any other ...
4
votes
1answer
36 views
Should I be concerned about spot corrosion on a telescope's primary mirror?
I am considering buying a telescope with a large primary mirror that is about seven years old - it has a small spot of corrosion on the mirror, that the owner says is stable.
Should I be concerned ...
4
votes
4answers
390 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?
2
votes
3answers
302 views
How could I translate a field of view value into a magnification value?
When I zoom in with Stellarium, it indicates a field of view (FOV) value in degrees, but most binoculars and telescopes are advertised with value like "nX magnification power."
How could I translate ...
8
votes
1answer
319 views
Why is the Ritchey–Chrétien telescope preferred in professional astronomy?
Hubble, as well as numerous other professional telescopes, use the Ritchey–Chrétien design. What optical and instrumental advantages does this kind of telescope have for professional astronomy?
6
votes
2answers
193 views
What makes a good set of binoculars? [closed]
After trying a bunch of binoculars at Star Parties and the like, I have a pretty good feel for about what aperture and magnification I'd like in a new set binoculars. I'm an eyeglass wearer so a long ...
20
votes
4answers
323 views
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 ...
5
votes
2answers
409 views
Optimal Angular Field of View (AFOV)
Given the rather huge price differences between eye pieces at the same focal length. How exactly does the AFOV affect the view seen through the eyepiece?
Are higher / lower AFOV better for certain ...
16
votes
6answers
899 views
Lenses (refractor) or mirrors (reflector) telescope?
What differentiates, in terms of practical quality, not technical implementation, a refractor from a reflector telescope?
Why would one prefer a refractor over a reflector, when reflectors come with ...
10
votes
4answers
2k views
What does f/4.6 mean in a telescope and how important is this value? [closed]
In some specifications for telescopes, I saw a value marked as f/4.6. What does it mean exactly, and how important is when it comes to choosing a telescope?
