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Questions tagged [telescope]

Questions related to the physical instruments for astronomical observations.

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-4 votes
1 answer
117 views

Which galaxy has the best view of Earth using telescopes like the ones we have?

By best view I mean most detailed view of Earth but I suppose you could also include the general surroundings such as the solar system.Perhaps this question also asks from where would aliens most ...
3 votes
0 answers
69 views

How to find the minimum range at which some imaging payload/instrument can produce a clear image?

JWST's NIRCam can image deep sky objects so clearly. However if we notice the images of planets like Mars, Saturn or Saturn's's Moon-Titan, they don't appear to be much clear. Hence considering the ...
5 votes
3 answers
620 views

Difference in field of view between JWST and Euclid

I was watching this video about the Euclid telescope. At the 8 minute mark he compares the field of vide of Euclid with that of the JWST, showing that the Euclid field of view is much larger. While I ...
0 votes
1 answer
34 views

Celestron X-Cel Barlow 2x magnification or Celestron X-Cel LX eyepiece 5 mm for 250P Dobsonian Sky-Watcher Telescope

I have recently gotten a Dobsonian 250P Sky Watcher Telescope and just wanted to ask whether it would be better to get a Celestron X-Cel Barlow 2x magnification or Celestron X-Cel LX eyepiece 5 mm, ...
13 votes
4 answers
2k views

Vera C. Rubin's LSST's ginormous camera's shutter; why does it open/close 1000 times a night & is this typical for large-format survey telescopes?

CNET's April 23, 2024 World's Largest Camera, the 3.2-Gigapixel LSST, Is Complete says after about 02:19 That shutter is actually so big it had to be broken down into two pieces just to fit inside ...
1 vote
2 answers
180 views

Given our current level of a technology, how far could we send a signal that we could detect?

I'm interested in both what we can do with things we've already built as well as things we could build (including with serious, but not insane amounts of funding). This would be a deliberate signal ...
1 vote
1 answer
82 views

What was the first nebulae of the first class?

On Wikipedia, it describes the Tarantula nebula as the second of the "Nebulae of the First Class", Wikipedia says that a Nebulae of the First Class is a Nebula with no other stars visible ...
4 votes
1 answer
406 views

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 ...
2 votes
1 answer
97 views

C8 Finder Rotates Freely

I have a Celestron C8 circa 1985 that I haven't used in about 20 years. The diagonal on the finder freely rotates. There is virtually no friction, so it won't stay where I want it. I don't see any ...
0 votes
0 answers
95 views

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 ...
1 vote
0 answers
29 views

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 ...
2 votes
1 answer
247 views

Telescope selection for concrete uses

Suppose I want to build or buy a telescope for the following uses: Astrophotography (mainly galaxies and nebulae). Transits of exoplanets and binary systems like Cygnus X-1. To search for BH+star ...
1 vote
1 answer
82 views

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 ...
0 votes
0 answers
159 views

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 ...
2 votes
3 answers
329 views

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 ...
1 vote
0 answers
71 views

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 ...
6 votes
1 answer
265 views

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 ...
5 votes
2 answers
218 views

What are the technological advancements that made it possible for modern large telescopes to work with alt-az mounts instead of equatorial mounts?

The video Earth's Rotation Visualized in a Timelapse of the Milky Way Galaxy - 4K (linked below) and discussion below this answer to Why does a timelapse video of a stationary Milky Way make the ...
2 votes
0 answers
58 views

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 ...
6 votes
1 answer
454 views

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 ...
6 votes
3 answers
598 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 £...
6 votes
4 answers
2k 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-...
2 votes
2 answers
103 views

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 ...
0 votes
1 answer
118 views

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 ...
4 votes
2 answers
3k views

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?
12 votes
1 answer
3k views

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 ...
1 vote
0 answers
53 views

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'...
5 votes
1 answer
565 views

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 ...
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 ...
1 vote
2 answers
375 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 ...
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 ...
1 vote
0 answers
133 views

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?
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 ...
8 votes
1 answer
566 views

General process of calculating what a telescope's diffraction spikes would look like?

I was reading this question about the JWST's diffraction spikes, and I was rather surprised by the magnitude of the 4 sets of diffraction spikes. The large hexagonal spike pattern I believe is formed ...
3 votes
1 answer
797 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 ...
3 votes
1 answer
539 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 ...
3 votes
0 answers
78 views

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 ...
3 votes
1 answer
315 views

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 ...
6 votes
1 answer
225 views

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 ...
2 votes
1 answer
75 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, ...
2 votes
1 answer
114 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 ...
2 votes
1 answer
187 views

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 ...
10 votes
2 answers
4k views

Why aren't reflector telescopes built with an offset secondary mirror?

Reflector telescopes (normally?) have a parabolic primary mirror that reflects the light to a secondary mirror which is placed at the center of the telescope. The construction holding that mirror and ...
3 votes
0 answers
137 views

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 ...
2 votes
2 answers
5k views

Black dot visible when looking into the telescope

A few weeks a go I bought a telescope. The problem is I am a total beginner. I was able to setup the telescope correctly and I already saw the moon very clearly. Then I moved on to jupiter. When I ...
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 ...
3 votes
3 answers
319 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 ...
6 votes
1 answer
413 views

Is seeing the Apollo Moon landers via an Earth-based telescope that hard?

There are interferometers that fuse the images produced by multiple telescopes and achieve a resolution of 0.001 arcseconds. With changes, couldn't these observe the Moon landers? Is the reason why ...
18 votes
1 answer
5k views

Is there any telescope on Earth that can see the lunar rovers on the Moon?

If I have the right numbers, it seems to me that even the Hubble telescope might barely be able to make out a carcass of a blue whale on the surface of the Moon, which puts objects as small as the ...
1 vote
1 answer
302 views

Can the interferometer called "Gravity" measure "a few centimeters on the Moon"?

Phys.org's Very Large Telescope sees star dance around supermassive black hole, proves Einstein right links to several ESO videos, including Interview with Reinhard Genzel (in English). After ...

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