Questions tagged [optics]

Behaviour and properties of light, and its interaction with matter, particularly in detection of light.

Filter by
Sorted by
Tagged with
8
votes
2answers
656 views
+50

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 ...
4
votes
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?
0
votes
1answer
73 views

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 ...
1
vote
0answers
40 views

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
votes
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
votes
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
votes
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
votes
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 ...
1
vote
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,...
1
vote
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
votes
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 ...
3
votes
2answers
108 views

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
votes
0answers
46 views

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 ...
4
votes
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
votes
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
votes
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, ...
2
votes
3answers
186 views

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
votes
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
votes
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? ...
1
vote
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
votes
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
votes
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/...
2
votes
0answers
48 views

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 ...
2
votes
2answers
62 views

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, ...
3
votes
1answer
122 views

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 ...
0
votes
1answer
141 views

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 ...
6
votes
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
votes
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 ...
11
votes
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 ...
2
votes
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. ...
0
votes
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. ...
3
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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 ...
1
vote
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 ...
3
votes
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
votes
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 ...
1
vote
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 ...
1
vote
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
votes
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
votes
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 (...
3
votes
2answers
19k views

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 ...
1
vote
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 ...
1
vote
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?
3
votes
3answers
2k views

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 ...