Questions tagged [optics]

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

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How did I flip some mirrors around in the dark at 3 AM and change the focal length of a 24 inch Boller and Chivens?

Current answer(s) to How do telescopes "zoom" and change angle of view? are "they don't", but traditional large genera-purpose observatory telescopes do sometimes (often?) have ...
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Are X-ray telescopes with glancing angle surfaces basically “funny-looking” Cassegrain telescopes mathematically?

In this answer I included the image below of a reflective X-ray telescope. It is made from two elements; the first is concentric shells of glancing (high incidence) angle paraboloidal surfaces, and ...
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What would “the next GAIA”-like instrument be like? Could it simply be a 3 to 5x scaled-up version of the same beautiful system?

This excellent, thorough and well-sourced answer to Has a gravitational microlensing event ever been predicted? If so, has it been observed? mentions several works where hundreds to thousands of ...
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Has lunar opposition surge ever been observed from Earth? From Earth orbit?

This thorough answer to How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter? details observations of lunar opposition surge by the Clementine ...
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How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter?

Wikipedia's opposition surge is a short article and forwards shadow hiding and coherent backscattering as proposed mechanisms, but it doesn't really explain how much the brightness of the Moon ...
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Telescope showing high chromatic aberration

Hi i have made a telescope with 1100 mm focal length objective lense and 21mm plano convex as eyepiece. Both these lenses are not achromatic. But when is looked through it , the images were completely ...
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Benefits to adding a 32mm Pössl to my Celestron AstroMaster 130EQ's eyepieces?

I am getting a Celestron AstroMaster 130EQ soon. I have heard that its eyepieces aren't the best, so I am considering a 32mm Pössl. For such a choice, what would be the arguments for and against? How ...
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What produces all of the small radial striations in this very overexposed image of a star by Hubble's WFC2? (the four big ones are from the vanes)

In a recent astrometry question in Space SE I needed to check Proxima Centauri's position and the article contained the image below. I've saturated the colors, cropped it, and added a "...
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How many photons does it take to determine the existence of a distant object?

This applies to any object, but I see the recent discovery of the oldest, most distant galaxy and it started me wondering what the limits are. Presumably you can do better with a bigger telescope and ...
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Magnification with a refractor

Using a refractor telescope at 200x, how close will an object appear at four miles away? Is there a table out there enabling you to calculate apparent seeing by filling in known variables?
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Can the “haze” of a mirror telescope be quantified?

When reading Why was StDr56 discovered only now? and its answers and comments, I realized that refractor telescopes, and in particular the Dragonfly Telephoto Array are a great tool to find nebula and ...
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Number of lenslets in wavefront sensor array

I have to do a short calculation, but, quite frankly, I have no idea how to even start... Suppose you have a 10-m telescope (f/10) with an infrared camera that observes at 10 micrometer. The seeing is ...
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Why are these telescope mirror makers not upside down? (Daniel K. Inouye Solar Telescope)

The new open access Solar Physics article The Daniel K. Inouye Solar Telescope – Observatory Overview is the first of several papers about the new state-of-the-art solar observatory. For more info see ...
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Are telescope eyepieces ever made with a diopter adjustment (similar to DSLRs)?

I am learning about eyepieces, and "eye relief" and what sorts of eyepieces an amateur may want for their purposes, and was wondering if there are eyepieces with diopter adjustments, or if, ...
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Shouldn't this cause a fire?

This website shows a telescope projecting the sun onto a blackboard: https://astronomyconnect.com/forums/articles/2-three-ways-to-safely-observe-the-sun.21/ Why isn't the board catching fire? You ...
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How to make a 65 cm lens with a 20 cm hole in it for a Hamiltonian telescope?

This answer to What (the heck) is a Hamiltonian telescope? Is this one? confirms that the telescope in the question linked there is indeed as described and that the first lens is a full 65 cm aperture ...
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What exactly is a Hamiltonian telescope? Is this one?

This comment on the current answer to Why is this telescope so short? How hard is it to make such a fast primary? says In this forum topic Borisov appears to call it an f/1.5 Hamiltonian. Wikipedia'...
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Deciding optical factors between a refractive and reflective space telescope optics as a function of aperture? (visible light)

Reading Yale News' Lighting a path to Planet Nine: To detect objects that are otherwise undetectable, Rice and Laughlin employ a method called “shifting and stacking.” They “shift” images from a ...
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What are Native coordinates in the World Coordinate System?

i am writing my first paper about our solar telescope, and i need to explain the optical transformations in terms of World Coordinate Systems. I am not sure if i got the following right, and would be ...
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How did Michelson measure the diameters of jupiter's moons using optical interferometry?

In Betelgeuse: How its Diameter was measured (Chant, C. A., Journal of the Royal Astronomical Society of Canada, Vol. 15, p.133, Bibliographic Code: 1921JRASC..15..133C) the author says: The paper in ...
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Eyepiece::Astromania or Meoptex

I am looking into getting a zoom eyepiece for myself, and not sure on what basis to evaluate and compare various options. For some background on the type of observing I plan to do see my earlier ...
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What's still needed before we can observe orbits of exomoons thereby weighing exoplanets?

Comments below this answer to How do we weigh a planet? point out that we currently cannot (or at least have not) detect moons around exoplanets, much less measure the sizes and periods of their ...
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Why does this large Newtonian telescope's front cover have two or three holes in it?

The Michael Bernardo video How to use an Equatorial Mount for Beginners shows a large Newtonian telescope on an equatorial mount. The cover of the telescope's large aperture shows what looks like ...
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Point spread function image deconvolution

I would like to deconvolve an image of Saturn. I took an image of Saturn: Stack of 50 frames, the angular resolution of the original frames is 1.6''/pixel and the frames are scaled x4 before stacking....
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What are the effects of using non-spherical lenses in refracting telescopes?

Non-spherical (or non-circular) mirrors for reflecting telescopes are common and discussed in many places... But what about elliptical, parabolic or hyperbolic lenses?
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A simple echelle spectrograph for viewing solar spectrum

On the Astrosurf website here, someone has designed a deceptively simple echelle spectrograph for viewing solar spectrum. Briefly, light from an optical fiber falls on an echelle grating and which is ...
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What is it about the layout of the three gratings in a Bahtinov mask that makes its indicate focus in this way?

The question Lucky imaging with Celestron 14 - is this result reasonable? includes a beautiful example of a focus test using a Bahtinov mask and the image below from Deep Sky Watch's Home Made ...
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Can a telescope ever increase the apparent luminance of an extended object?

From what I know about common telescope designs, telescopes don't increase the apparent luminance of extended objects compared to the luminance seen with the naked eye. In this sense extended objects ...
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Precise meaning of collimation/alignment of a binocular

My question is about what exactly is meant by a binocular being collimated/aligned. I'm familiar with optics in general, but not with the nitty gritty of binocular design. There are various resources ...
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Telescope focal length, reducer and/or Barlow

Say I have a scope with a given diameter $D$, a given focal length $f$, and a given exit barrel diameter $B$. It has a maximum true FoV of $B/f$ (supposing $B<<f$). Would adding a 0.5x focal ...
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How to chose a comfortable 2 inch eyepiece for a Skywatcher Dobsonian 150 mm f/8 reflector?

Totally newbie here. I got the Skywatcher Dobsonian 6 inch (150 mm) f/8 Newtonian reflector. I had a brief chance to test it yesterday when the skies here in Melbourne cleared a little bit. I was able ...
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What kind of halo is this?

My friend sent me a video of a kind of a halo phenomenon and asked me what kind of halo it is. There is a 22 degree circular halo around the sun. But there is also a ring which seems to go ...
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Have there been studies of “old photons” to see just how constant things like Planck constant has been?

The question Are photons aged? and answers therein have got me thinking: I vaguely remember hearing something about experiments where "old photons" were collected by large telescopes from very ...
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Does this CHEOPS first light image imply bad astronomy?

@KeithMcClary's comment under lousy mirror corrected by software links to Bad Astronomy's First Light for the Exoplanet Hunter Mission CHEOPS Goes Tetrahedral which shows the image below. I understand ...
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When are wedge prisms used to correct chromatic effects of atmospheric refraction?

Atmospheric refraction (shown below) happens because Earth's atmosphere has an index of refraction that differs from unity. @MikeG's comment mentions that this refraction would have a chromatic ...
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Voyager 1 and 2 detected a 20-fold increase in plasma density, significantly different refractive index?

As reported by Nature.com, Voyager 1 and 2 detected a 20-fold increase in plasma density going from the heliosphere out to interstellar space. Does that 20-fold difference in density imply a ...
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Optics: “Airy disc” and size of objects

Jupiter has a minimum brightness that is brighter than stars. Is the reason an “airy disc”, concentric rings as a diffraction effect, is seen around stars and not Jupiter because Jupiter has an ...
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Stellar aberration, any prism effect?

In stellar aberration, is there any prism effect, chromatic aberration?
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How can I determine if a typical low-end telescope is a refractor or reflector?

Is there a way to distinguish (with no manual, product info etc)?
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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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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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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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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 ...
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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 ...
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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 ...
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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 ...
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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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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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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 ...
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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 ...