Questions tagged [optics]
Behaviour and properties of light, and its interaction with matter, particularly in detection of light.
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How exactly will DESI simultaneously capture individual spectra from 5,000 galaxies using optical fibers?
The BBC News article Telescope tracks 35 million galaxies in Dark Energy hunt says:
The aim of the five-year programme is to shed light on Dark Energy - the mysterious force thought to drive an ...
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1answer
266 views
Split telescope into two eyes
I am looking for an appendage to attach to the end of a telescope which splits the image into two eyes instead of one.
Does such an appendage exist?
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1answer
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Questions about amateur astrophotographer Nik Szymanek's telescope
The 2011 Sixty Symbols video Spy Satellites (from Deep Sky Videos) shows amateur astrophotographer Nik Szymanek and his telescope.
Question: Can someone identify the model and design of this ...
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0answers
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PSF magnification
I have a circular telescope pupil, a magnifying optic, and a detector. I am trying to calculate the point spread function as a function of wavelength. I am running into the issue that Python's 2D FFT ...
0
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1answer
71 views
Does anybody recognize this kind of prism?
Supplemental to this answer to Did Edmund Scientific 4¼ inch Newtonians have 90° prisms as secondary mirrors in the 1970's? I was poking around a bit further and ran across this "1960's Edmund ...
2
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1answer
29 views
Telescope focal point and inversion
When looking at a diagram of the optical path through a newtonian reflector, the lines always cross before the eyepiece. I understand that the eyepiece is used to focus this diverging light cone so ...
2
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1answer
78 views
Why are Shack-Hartmann sensors so expensive (4k+ USD)?
Recently I am searching for a Shack-Hartmann wavefront sensor for university laboratory usage. I was expecting my target sensor to be cheap, which is:
Low spatial wavefront resolution (50 x 50) for ...
14
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3answers
2k views
Why different specifications for telescopes and binoculars?
Sorry for the noob question but I don't seem to be able to find the answer on the internet.
I've been looking through some telescopes and binoculars and noticed that shops typically give different ...
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1answer
56 views
How are “parallel fields” implemented on the Hubble Space Telescope?
The Phys.org news item Hubble is the ultimate multitasker: Discovering asteroids while it's doing other observations mentions the Hubble Space Telescope's use of parallel fields:
A couple years ago,...
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1answer
133 views
How to find the source of the light? [closed]
There are millions of galaxies out there in the entire universe. When a telescope is set to a direction to to identify the stellar objects, it can capture all lights from all the objects. How do we ...
2
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0answers
71 views
Why look at an infrared telescopes's mirror with ultraviolet light? (Herschel Space Observatory)
While link-clicking for Where did Herschel Space Telescope go in 2013? I ran across the 2009 Time Magazine article Two Telescopes to Measure the Big Bang which shows the file photo below with the ...
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2answers
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What would be the obstacles to building a 6.5km space telescope besides cost?
In the comments of another question on this Stack Exchange site, I talk with another user about the possibility of building an optical space telescope with a 6.5 km aperture.
Obviously, this is much ...
2
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0answers
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Within a given image of a multiple-image producing gravitational lens, does Fermat's principle apply?
The question Does gravitational lensing provide time evolution information? is excellent!
When we see multiple images of the same object because of the phenomenon of gravitational lensing, do all ...
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3answers
201 views
Why does the Moon appear to be flat?
There's no way around it: when I look at the full moon at night it looks like a mostly flat disc, with at most a bit convexity in the middle. Phases of moon look like a full moon seen through a cut-...
6
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1answer
156 views
Angular diameter of the Sun's reflection from the ocean, seen from Sun-Earth L1?
I'm trying to understand how smooth the reflecting ocean surface would need to be to produce such a small bright spot as seen from the DSCOVR satellite at Sun-Earth L1. It appears to be only about 8E-...
2
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1answer
373 views
How does making a refracting telescope very long reduce the chromatic aberration of an uncorrected lens?
Below are two cropped views of "Johannes Hevelius's 8 inch telescope with an open work wood and wire "tube" that had a focal length of 150 feet to limit chromatic aberration." from Harvard University, ...
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3answers
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How did Johannes Hevelius' long telescope work? Why all the round holes?
The drawing below, found in Wikimedia and at lib.harvard.edu is of a very long tubed aerial telescope. I believe it is taken from his 1673 work Machinae coelestis.
I've always wondered about the ...
2
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1answer
46 views
What are some formulas that are associated with the Schmidt corrector?
I want to fully understand how an SCT works. Thus, I figured out I can use some formulas that describe how an incident ray that is parallel with the axis would act after refracting off a Schmidt plate....
2
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2answers
171 views
What are the aberrations of an SCT? And how can they be eliminated?
The Schmidt-Cassegrain telescope is amazing! It is compact, suitable for astrophotography ,and it requires little to no collimation. However, the SCT has some inherent optical issues. What are they? ...
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1answer
90 views
Why aren't corrector plates aligned with the center of curvature in an SCT?
According to wikipedia, Schmidt corrector plates must be aligned with the center of curvature to eliminate the spherical aberration. However, in compact SCT designs by Celestron and Meade, that is ...
3
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3answers
153 views
Advice on first Telescope (refractor vs reflector), Barlow lens
I am planning on buying my first telescope. I am getting an 80mm refractor and a 114mm reflector for the same price range. Which would be a better option? Further, would a Barlow lens solve the ...
3
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0answers
173 views
Are they really sure this isn't an Airy disk? How was that ruled out?
How do they know that this is a spherical shell of gas, and not just something like an Airy pattern-like artifact produced by the VLT's large interferometric aperture?
Image from: https://www.eso.org/...
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0answers
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Does Arecibo's secondary optics compensate aberrations when viewing farther away from vertical?
In the beginning of the short YouTube video Arecibo Uncut: Under the Dish with Phil Perillat it is mentioned that while dish antennas are usually a parabola, the problem is that a static parabola ...
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2answers
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Arago Spot in the Shadows of Celestial Bodies
Recently, I've watched this video by Veritasium describing Poisson's Spot, or the Arago Spot. It is explained in the video that near circular (or spherical) objects can produce this optical effect, ...
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1answer
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What is the cause of all of these sharp, concentric rings around bright stars in this HST image?
ESA's HST page heic1819 — Photo Release; Hubble reveals cosmic Bat Shadow in the Serpent’s Tail is of course beautiful and stunning, but my eyes are drawn to the diffraction artifacts of the bright ...
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1answer
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Why does the sun appear 13x bigger through diffraction in Voyager 1 image from 1990, but not from Earth? [closed]
The sun in the Voyager 1 photo here from 1990 appears 13x bigger than its diameter, diffraction of course. On Earth, photographs of the sun do not make it appear 13x bigger. Why?
A description of the ...
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1answer
133 views
Why are there optical differences between sunrise and sunset?
I've noticed that sunrises are not reverse sunsets regarding the sky hues and lighting.
Sunrises always start pinkish and end with a glorious yellow sunshine.
On the other hand as the sun sets ...
7
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4answers
271 views
Where exactly is the modification that first corrected the spherical aberration in Hubble's primary mirror?
The April 2015 CBS News article How NASA fixed Hubble's flawed vision - and reputation describes the modification taken to the Hubble Space Telescopes by the Space Shuttle that was used to correct for ...
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3answers
639 views
Has anyone ever tried to make a simple telescope using ice?
I grew up with long cold winters, and saw a lot of remarkably transparent ice formed by refreezing meltwater, both in puddles and ponds, and in large icicles. I'd always thought about making optical ...
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1answer
135 views
What is a pupil slicer, and how does it work with anamorphic optics in VLT's ESPRESSO Echelle spectrograph?
This excellent answer points to ESPRESSO, - Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations. From there I looked at the Instrument Description and Performance page.
...
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1answer
246 views
Why does the sky look like it has three suns in this video? [closed]
Check out @natalie9280’s Tweet:
long story short, friday morning at around 6:40am i looked outside and i saw three suns.
i checked to see if there was an eclipse and i could[n't] find anything.
...
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1answer
100 views
How to understand Kepler telescope under large aspherical wavefront
To my understanding, a Kepler telescope is designed to conjugate one plane to another. For example scale down/up the incoming wavefront onto a wavefront sensor for measurement. It works well for small ...
2
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1answer
143 views
Telescope and its construction
I want to build a reflecting telescope in my home. I've attached a drawing of my plan that contains some explanations of what I understand so far, and highlights the parts of the design for which I ...
3
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0answers
51 views
Is it possible to model a solar thermal concentrator using Zernike polynomials?
This question might seem a bit off-topic, but I guess there are a lot of people here that know about optics, telescopes, etc.
I would like to simulate solar thermal systems that focus solar ...
2
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1answer
70 views
How well can the Sun's surface be resolved by an observatory?
There's no lack of photons, how well could a telescope resolve Sun spots and other surface features of the Sun? How would a high resolution Solar (space) telescope differ from for example Hubble which ...
8
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5answers
317 views
Are there any mirrors in space?
We have encountered galaxies that act as lenses, magnifying the light coming from behind them. This is super fascinating and it makes me wonder what other optic tools we might have at our disposal.
...
3
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1answer
474 views
How do tip tilt mirrors correct distortion in adaptive optics?
I'm currently trying to learn about how adaptive optics correct the blurriness caused by atmospherical seeing effects. This is my current understanding of how adaptive optics works (trying to offer ...
3
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3answers
533 views
Projecting an image of the sun / eclipse
This might be an astronomy.stackexchange.com question, but I think it is more in line with a camera obscura.
During the last eclipse I didn't plan ahead and grabbed some lousy toy "spy" telescope we ...
2
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1answer
180 views
Why is this HST WFPC2 image so much fuzzier than the WFC3 image of the same field?
I was looking at the comparison of 2007 and 2015 HST images of the "disappearing" star N6946-BH1 in Phys.org's article Collapsing star gives birth to a black hole. The 2007 images is from the WFPC2 ...
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1answer
123 views
What telescope is this, and how does it work?
In the excellent chemistry series of Periodic Videos' episode Amazing piece of metal (speculum) there is an interesting showing and discussion of Isaac Newton's first telescope.
At ...
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1answer
1k views
Constructing a periscope/telescope - trouble with lenses
Not sure if this is the best place for this, maybe physics would be a better fit, but I'm trying to build a periscope and am running into an issue.
Traditional mirror periscopes work well, but when ...
0
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1answer
117 views
What could have made a satellite appear to move side to side while near the horizon?
Yesterday while coming out of a restaurant my wife and I noticed what appeared be a satellite passing quite high in the sky. Based on the location, time, and brightness this appears to have been a ...
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1answer
338 views
Lunar terminator illusion
Sometimes, you can see the Moon high in the night sky, which is illuminated from the side where Sun goes down but slightly from above. It is paradoxical when Sun hangs at the lower level above the ...
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2answers
122 views
Is there a spectrum of polarization? Does polarization vary depending on wavelength, from one and the same source?
Is it possible, and does it occur naturally, that the light from the same source is simultaneously polarized differently at different wavelengths? Light can be polarized by interstellar magnetic ...
3
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1answer
124 views
Can a telescope be built to focus on a point source star?
If a Kepler telescope were built to focus on one point source star at a time, would it provide more information, or did Kepler capture virtually every photon from any given star anyway?
In order to ...
2
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1answer
769 views
What is the faintest magnitude a telescope can see?
This website claims:
The space telescope can detect objects as faint as 31st magnitude...
It's referring to Hubble, but does not cite any source or math. How do you calculate the faintest (...
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2answers
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How to make a telescope for viewing planets, moon and DSOs using a convex lens of aperture 100 mm and focal length 200 mm and other lenses at home?
I wanted to make a telescope with DIY things lying around in home. I read up that the aperture was a very important aspect and thus bought a convex lens with 100mm aperture and 200mm focal length, to ...
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1answer
362 views
Magnification of a telescope
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
...
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2answers
209 views
What is the longest observable wavelength of light using an optical telescope?
How far outside the visible spectrum could an optical telescope feasibly operate?
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3answers
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Dish antenna as parabolic mirror for OPTICAL telescope?
Can I use a chrome painted dish TV antenna as a parabolic reflector for my optical telescope? Given that glass mirrors are quite expensive, I am thinking of using a Dish TV antenna and coating its ...
