All Questions
120
questions
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40
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Assessing the quality of wavefront correction in adaptive optics systems: the case of single and multiple radiation sources
Generalized diagram of an adaptive optical system is as follows:
Wavefront from the observation object passes through the atmosphere and is distorted. It is then reflected from the deformable mirror ...
- 139
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0
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29
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How is a complete image of a distant object formed with an obstruction in the line of sight? [duplicate]
Can anyone please link to or sketch a diagram demonstrating how a complete (and clear) image can be formed of a distant celestial object with a central obstruction blocking part of the line of sight ...
- 101
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19
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The expectation value of intersecting particles
If I have a light beam (a straight line)
it goes through a box of dust, which has travelling length $l$, dust molecule cross section $\sigma$, dust number density $n$.
how to calculate the expectation ...
- 157
2
votes
1
answer
35
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Advantage of a single large telescope over many small ones for optical/infrared spectroscopy?
In a thought experiment where we would like to do optical/infrared spectroscopy on distant galaxies, and in which we would like to increase as much as possible the resolution of the spectroscopy (...
- 1,109
1
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65
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Have we independently verified Leavitt’s luminosity-period relationship?
After Henrietta Leavitt discovered the relationship between luminosity period amongst cephids in the Magellanic Clouds, how was she so sure that you can extend this relationship to other Cepheids ...
- 21
1
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97
views
Why does the Moon - which is grey - appear white to us even at daytime?
The color of the Moon as viewed more closely, is grey. But when we see it in the sky it appears white to us. Why?
Although this question has some answers here: Why is the surface of the Moon white? (...
- 411
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2
answers
140
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How can photons be emitted from a star, travel millions/billions of years in a "straight line", and be seen by two adjacent observers?
If photons are emitted by a star and travel millions/billions of years in a "straight" line, they can be seen by adjacent observers. This makes it seem like there must be an uncountable ...
- 23
1
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53
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A noon cannon with two lenses
A noon cannon usually has a single convex lens which focuses sunlight onto a fuse. The cannon contains gunpowder. The fuse ignites and the gun discharges at noon.
https://en.wikipedia.org/wiki/...
- 13
1
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0
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73
views
If you had an indestructible disk, where would you place it to block the most energy from the sun? [closed]
Imagine you have an indestructible, opaque disk, (say 100m in diameter), and you want to place it between the sun and the earth to block the most energy from hitting the earth.
Some assumptions:
We ...
- 111
1
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1
answer
66
views
Resolution: Telescopes vs. Camera Objectives
Telescopes and Camera Objectives are both optical systems which image objects from far away to a finite image distance. Although camera objectives are often used for finite object distances, in most ...
- 247
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67
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How is Starlight Reflected by Mirrors?
The chosen star is on the Z-axis of Mirror-A (Red). The Star image appears on the
face of this Mirror at the Origin of the CoSys.
Starlight Rays (Yellow lines) remain parallel, and do not diverge with ...
3
votes
2
answers
77
views
How deep can a 'deep field' image be?
Hubble's famous deep field image was created by pointing the telescope at the same spot for 10 days continously. This aggregates photons and creates a coherent image - If I understand what's going on ...
0
votes
1
answer
57
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Project Apollo Sextant Beam Splitter - How did it work?
MIT's Role in Project Apollo Volume 2 Optical Subsystem
Apollo Sextant Beam Splitter
For onboard navigation to and from the Moon, a sextant was used by Apollo astronauts
to measure the angle between ...
3
votes
2
answers
971
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The Resolving Power of a spectrometer
I can't understand one thing in the definition of the resolving power of a spectrometer:
Let the resolving power be defined as: $R=\frac{\lambda}{\Delta \lambda}$ where $\Delta \lambda$ is the ...
- 941
3
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1
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148
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In what sense is the JWST image of Jupiter an improvement over prior telescopes?
JWST photographed Jupiter:
The data includes images of Jupiter and images and spectra of several asteroids... The data demonstrates Webb’s to track solar system targets and produce images and spectra ...
- 5,148