Questions tagged [telescope]

Questions related to the physical instruments for astronomical observations.

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Largest Optical Telescope NOT at Higher Elevation

It's trivial to find the list of largest optical telescopes by aperture size. What I'm interested in is the largest optical telescope in the world, regardless of ownership or origin (amateur or ...
Chris's user avatar
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Published magnitude limits of surveys

I'm working with several astronomical catagloues (mostly SDSS, GALEX and WISE), and I'm trying to find information on their magnitude limits (i.e. the highest magnitude objects they can detect). They ...
Jim421616's user avatar
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Why do we call radio images "maps"? Is it because it is not optical, so therefore not an "image", strictly speaking?

Or is it just historical convention? I know that within research circles, it is common to also use the term "radio image". I am mainly wondering whether the term originally comes from ...
Loika's user avatar
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Do solar eclipse paper glasses need to list both the ISO and CE stamp to be compliant or is the ISO sufficient?

I purchased them at the checkout at Walmart. They are Manufactured by American Paper Optics, LLC. Visionscientific.com ISO 12312-2. However I don't see the CE on the glasses. Are they still OK? The ...
Sedumjoy's user avatar
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2 votes
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Will there be a difference in what can be seen with a 50mm telescope and a 70 or even 80 mm one?

tl;dr Is there a celestial object which has details that can be seen clearly by a 70mm telescope, but no details at all seen by a 50mm telescope of the same make. E.g. "Jupiter has details that ...
ispiro's user avatar
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About telescope load

I am using planewave CDK24 Telescope. The focuser I am using is IRF90 which has maximum load capacity of 18 kg. The load that I am going to attach is 14 kg. Is this alright to attach this weight? Is ...
Tumpa's user avatar
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6 votes
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First photographic image taken with telescopes to produce astronomically useful results? What telescope was used?

comments on the question and answer(s) to What are the technological advancements that made it possible for modern large telescopes to work with alt-az mounts instead of equatorial mounts? have made ...
uhoh's user avatar
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With a non-motorized telescope, can 100 pictures of 0.5 seconds be realigned and merged to get the equivalent of a 50-second long exposure shot?

I have a non-motorized Newton 130/900 telescope. Of course, it's hopeless to do pictures with exposure ~ 1 minute. Even 1 second is probably too much, as seen in Optimal exposure time for photography ...
Basj's user avatar
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What were the specifics of the photos taken by Sir Arthur Eddington during the Eddington expedition that supported Einstein's Theory

I know that Sir Arthur Eddington went to South American to photograph stars around an eclipse to see if they seemed to change position when the light past by the Sun relative to when the light didn't ...
Elliott Cooper's user avatar
6 votes
3 answers
503 views

Is it practical to build a DIY spectroscope that can clearly show absorption lines in a spectra of the Sun?

Is it practical to build a DIY spectroscope that can clearly show absorption lines from the Sun? "Practical" means that the kit can be made at home or relatively cheaply bought (less than £...
Slarty's user avatar
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Could we hear alien radio transmissions using radio interferometry?

Suppose money and engineering wasn't a concern. Could we actually build a bunch of radio telescopes in space, and use radio interferometry, so that we could actually hear the sort of radio ...
Adrian's user avatar
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If 42000 Starlink satellites interfere with telescope observations from Earth would someone observing from another solar system detect them too?

SpaceX's Starlink constellation could place up to 42000 satellites around the Earth. Would aliens with their own telescopes notice them? They would be about 150 km apart and could reflect light of ...
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4 votes
2 answers
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Which place in the world should be best for astronomy with an optical telescope?

Would it be somewhere in a desert a long way from water and mist, or high on a mountain above the lower atmosphere? Where is the best location in theory or in practice?
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12 votes
1 answer
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Are there plans to detect life on Earth from the outer solar system?

This has been kicking around in my head for a while. We've been detecting planets for decades by observing regular dips in starlight from many light years away as a planet transits its host star. I've ...
Greg Burghardt's user avatar
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How do eyepiece mm values equate to telescope tube extension mm values?

I'm trying out a DSLR on my Celestron 70EQ refractor telescope with a DSLR T-ring. The first try didn't magnify very much, and I learned that I need to extend the focus length to magnify the image; I'...
KJ7LNW's user avatar
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Would it be possible to use existing radio-telescopes to do spot measurements of CMB?

With CMB peaking at roughly 158GHz would it be possible to create a more precise map of CMB just by sampling 'points' using existing Earth-based radio telescopes? I understand that large dish ...
user2820052's user avatar
21 votes
3 answers
6k views

How can telescopes see anything at all?

I'm impressed that we have any telescope imagery at all. Take the images we have from the "Pillars of Creation". The Pillars of Creation is in the Eagle Nebula, some 7,000 light-years away ...
Victor Debone's user avatar
1 vote
2 answers
331 views

Can telescopes under $200 help you see saturn clearly by eye without editing the image on a computer?

I had a telescope that only cost 50 dollars for viewing the moon and it was good for that but the planet's were always badly out of focus. I am thinking of getting a better telescope for up to $200 ...
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6 votes
2 answers
4k views

What kind of telescope would be needed to image a 10m dim object 1 million km away?

There's a 10m diameter object 1 million km away from you, stationary with respect to you. The object is dim: it is at 3K and is not reflecting any light towards you. So you have to pick it out by the ...
causative's user avatar
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How to spot Andromeda in a 130mm telescope?

I have no problem to spot orion nebula, I mean the blue splash caused by the gas on my 130mm reflector telescope but I can’t see the same on Andromeda, what I am missing?
David Bemerguy's user avatar
10 votes
3 answers
2k views

Why are segmented mirrors lighter than monolithic mirrors?

Everywhere I look, it is recited as a quasi-mantra that "segmented mirrors are much lighter than monolithic mirrors", and I can't manage to find an explanation anywhere no matter how hard I ...
David Cian's user avatar
3 votes
1 answer
626 views

Is there a maximum practical telescope aperture for viewing (through a filter) a solar eclipse?

I grew up stargazing through various telescopes of increasing aperture sizes, and now that I can afford it, I'm about to invest in a more serious telescope to suit me for decades to come. My primary ...
Nick Williams's user avatar
3 votes
1 answer
460 views

Why do planets just look like a dark ball in my telescope

I bought a Matsukov Cassegrain many years ago and now wanted to dust it off and use it. I had two young kids at the time so couldn't really find the time. Last night Jupiter and Saturn were both ...
Francesca Bahr's user avatar
3 votes
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What instruments do amateur astronomers use in their ground based telescopes in order to avoid atmospheric absorption/telluric contamination?

What instruments do amateur astronomers use in their ground based telescopes in order to avoid atmospheric absorption/telluric contamination? For example, when an astronomer observes a celestial body ...
Arjun's user avatar
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Attachment for viewing the sun with a telescope

In 2016 I got to see the transit of Mercury thanks to a group of volunteer astronomers. The astronomer had a device attached to the telescope eyepiece that allowed the light to project onto frosted ...
bugloaf's user avatar
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1 answer
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Mauna Kea versus Mauna Loa: Astronomy ethical considerations

There have been controversies and conflicts related to telescopes/observatories developed on Mauna Kea, as described here. However, there does not seem to be controversies related to observatories on ...
festivevanilla's user avatar
2 votes
1 answer
73 views

What eyepiece or other optics might improve image quality or observing experience for my Shilba Eclipse 60900 telescope?

I have an old Shilba Eclipse 60900 telescope. Specs: Object diameter: 60mm Focal Distance: 900mm. Optics: Barlow 3x 1.5x Erecting Eyepiece 4mm and 12.5mm eyepieces. I'm aware it's a basic one, ...
Facundo zanatta's user avatar
2 votes
1 answer
111 views

How are the Extremely Large and Thirty Meter Telescopes coming along ("planned 2027")

The graphic above is oft-cited in SE questions and answers. I was (a little) sad to see in it that the 100 meter telescope-engineering wunderkind Overwhelmingly Large Telescope or "OWL" has ...
uhoh's user avatar
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2 votes
1 answer
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Is there a reflecting telescope like as a Newtonian telescope but with a negative lens before the diagonal mirror?

A Cassegrain reflecting telescope contains a negative optical element between the main mirror and its focus. This increases it's focal length. Is there a reflecting telescope like as a Newtonian ...
Imyaf's user avatar
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Getting good images only when I cover the part of telescope opening

I have recently built a 4.5inch reflector telescope. The primary mirror is of 900mm focal length. The issue is, when I try to observe Saturn I am not getting good images. It looks like kind of double ...
sanoj's user avatar
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4 votes
1 answer
2k views

If the universe were infinite, how would it look through a telescope?

I assume there is some limit to how far our telescopes could actually see, and that this distance would be about the same in all directions. So, as a layman, I would assume that an infinite universe ...
hermancain's user avatar
14 votes
2 answers
1k views

What telescope is Polish astronomer Kazimierz Kordylewski holding in this April 1964 photo at the Jagiellonian University Observatory in Krakow?

The following questions touch on Kordylewski clouds Can dark matter accumulate at Lagrange points? Are dust-dust collisions necessary to explain Kordylewski clouds at Earth-Moon L4/5? Aren't the ...
uhoh's user avatar
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31 votes
1 answer
6k views

Why did it take so long to invent telescopes given glass was used 4000 years ago in Mesopotamia?

Is a telescope difficult to make? Does glass have to be polished and shaped very precisely? Or is a device using two or more lenses to magnify things just not obvious?
user avatar
2 votes
0 answers
125 views

How did people in Mali know that there were two stars appearing as one in Sirius before telescopes were invented?

Did they invent a telescope and keep it quiet? Given that glass has been around for 4000 years (made in mesopotamia in 2000 BC) was it technically possible to polish it and make convex shapes from it ...
user avatar
3 votes
3 answers
242 views

Apart from higher costs, drawbacks of catadioptric telescope vs Newtonians?

From what I've read, catadioptric telescopes seem to be superior to reflectors. They tend to require less frequent collimations, are generally shorter in physical length, and the combination of lenses ...
scijam's user avatar
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3 votes
1 answer
122 views

Trouble seeing Mars and Venus more than specks of light

Finally been breaking out the telescope to get a better look at things recently, and have been attempting to take advantage of Mars's and Venus's positions in the sky, but I haven't been able to see ...
BeardedChemist9's user avatar
5 votes
1 answer
493 views

Which telescope(s) did Charles Messier use to catalog his 110 objects?

Charles Messier is known for (among other things) a catalog of "Messier objects". Neither article shows an image of "Messier's telescope", though the latter includes: Since these ...
uhoh's user avatar
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2 votes
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35 views

Which value of the apparent magnitude do I use from a Supernova light curve

I am trying to get the distance modulus from a light curve of a supernova and obviously the apparent magnitude changes with time. Not only that but there are so many filters with different mags. So my ...
Abdullah's user avatar
1 vote
0 answers
72 views

Ritchey–Chrétien telescope with a short back focus

I have an observing project that requires a 30 -- 40 cm (12 -- 16 inch) diameter primary and no refractive/transmissive elements (i.e. lenses). Telescopes like this Ritchey–Chrétien has a back focus ...
Nicholas's user avatar
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2 votes
1 answer
196 views

Right ascension of a star and local sidereal time

If I'd like to watch star like Betelgeuse that has coordinates - right ascension 05h 55m 10.30536s and declination +07° 24′ 25.4304″. If my local sidereal time is 05h 55m 10.30536s does it mean that ...
pacman's user avatar
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25 votes
2 answers
7k views

Was Galileo expecting to see so many stars?

Beginner amateur here. I see mentioned many times that Galileo was surprised to see the moons of Jupiter and all that their existence proved, i.e. the Earth not necessarily being the center of ...
Theodore's user avatar
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1 vote
1 answer
92 views

Telescopes with equatorial mount and "catching" stars

I have a misunderstanding of principles behind using telescopes with equatorial mount (I don't have it yet, only trying to grasp the idea). For example, I would like to watch Betelgeuse in the ...
pacman's user avatar
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1 vote
3 answers
78 views

Is rayleigh's criterion only applicable to refractive telescopes?

Can we apply Rayleigh's criterion for the resolution of a primary mirror of a reflective telescope?
Tapan Gupta's user avatar
2 votes
1 answer
144 views

What is the diameter of a telescope lens that will capture the surface of Proxima Centauri b?

I been trying to find the way I can calculate the telescope lens diameter needed to see a star by the distance of the star or the planet from the earth. Is there any mathematical relation we usually ...
xone-a's user avatar
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1 vote
1 answer
77 views

Can we see the colorful patches or the strip of milky way galaxy with reflector telescopes?

As reflector telescopes gather light and make dimmer images brighter, so if I viewed through telescope with 1x magnification or viewed the horizon ,would I see the strip of milky way?
Tapan Gupta's user avatar
1 vote
0 answers
130 views

Can we use plain mirror as a secondary mirror in cassegrain telescope?

I was planning of making a telescope like JWST, just with plain mirrors, as bigger concave or convex are much expensive. The primary mirror would be totally made of plain mirrors configured like JWST. ...
Tapan Gupta's user avatar
6 votes
1 answer
752 views

For lenses, what is the practical difference between plano- and bi-?

I don't know if this is a trivially obvious question for astronomers. If so please forgive my ignorance. I've looked around at a lot of diagrams of lenses in telescopes. The plano-convex and bi-convex ...
DrZ214's user avatar
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3 votes
1 answer
352 views

Why does the altitude-azimuth mount have a blind spot near zenith?

I understand the subject mathematically. Azimuth of the celestrial object under track changes a finite 180 degrees instead of a infinitesimal amount as the body passes zenith. This would require ...
Cici Xu's user avatar
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2 votes
1 answer
128 views

Could two-way mirrors be used to completely eliminate obstruction for a reflector telescope?

The secondary mirror on a reflecting telescope obstructs some of the light coming in and the spider vanes that hold up the secondary mirror cause diffraction spikes when imaging. Some people prefer ...
chowder's user avatar
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4 votes
1 answer
221 views

What is the probability that a photon that enters the aperture is registered?

If I want to derive the probability that a photon that enters the aperture of a telescope is detected, how do I do that? This should be closely related to the quantum efficiency of a telescope, but ...
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