Questions tagged [telescope]

Questions related to the physical instruments for astronomical observations.

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9
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3answers
198 views

Why are telescopes positioned in Lagrange points?

In this Wikipedia article about the list of space telescopes to be launched (which I assume is exhaustive), of the 11 telescopes yet to be launched, 6 will be positioned at the Sun-Earth L2 Lagrange ...
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1answer
120 views

How does diffraction occur in a reflecting telescope?

It's understandable how diffraction occurs in refracting telescopes, because the lens itself is a small aperture for light to pass through. But what about reflecting telescopes? Since light is ...
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2answers
185 views

Why are Cassegrain telescopes shorter than Newtonian reflecting telescopes?

Many websites say this is because the effective focal length of the objective is increased by making the secondary mirror convex. This allows a Cassegrain telescope to be shorter than a similarly ...
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4answers
411 views

How do focal length, angular magnification and field of view relate?

The larger the focal length the larger the angular magnification The smaller the focal length the larger the field of view. I don't understand why this applies. I'm talking specifically about ...
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2answers
116 views

Why are larger hex mirrors round and the smaller aren't?

Per this diagram why are the larger (30 meter and European) mirrors filled out to nearly a full circle, while the smaller mirrors composed of hexagons retain a hexagonal border limit instead of ...
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3answers
2k views

Astronomical telescope making

I am thinking about making a telescope. I have a 100cm focal length lens which I can use as objective lens in my telescope. So which is the best focal length I can use as eyepiece in my astronomical ...
3
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2answers
112 views

Is looking through a telescope to do astronomy a thing of the past?

Do astronomers actually look through a telescope with the naked eye or do they mostly look the the data generated by telescopes on computers? Are they mostly working behind the computer and pencil ...
8
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2answers
755 views

Which telescope's model is being shown to Albert Einstein in this file footage? What event might this be?

In the Economist video Why does time pass? there is some file footage of Albert Einstein attending some event where a model of a large telescope is on display, and being described to Prof. Einstein. ...
6
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2answers
251 views

Why not us interferometry to take a picture of Pluto?

Interferometry is among the best ways (if not, the best way!) to have an image of a very distant object. Recently a picture of the black hole at the center of M87 was released. It is the result of ...
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1answer
72 views

lousy mirror corrected by software

Would it be possible to get a terribly shaped mirror, like a large sheet of something reflective, give it a general shape like a telescope mirror, but not anywhere near as precisely shaped as in a ...
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2answers
2k views

Space telescope located in outer solar system

I want to pose a question from someone who's astronomy knowledge would fit neatly onto a single piece of paper so please bear this in mind with any comments or answers. I am interested and want to ...
3
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1answer
73 views

What could I resolve with my Telescope

I recently won a Common 50mm refracting telescope with Solar Filter too.. I'm trying to Understand things I can skygaze with it. It's pretty basic and I should have known. Unfortunately, I don't ...
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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 ...
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0answers
44 views

How was astronomical data meant to be handled on HST precursors?

The first drafts for a large space telescope such as Hubble were made in the 60's, and the idea of a space observatory originated long before that. From Wikipedia: In 1968, NASA developed firm ...
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3answers
203 views

What's the cheapest lens to buy for showing ISS to a flat earther?

Recently I entered a discussion with someone that has a relatively popular YouTube channel which says among other things that the earth is flat. I said that earth isn't flat because you can see the ...
6
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1answer
216 views

How does the black hole at the center of M87 look like in the visible spectrum?

I learned here that the picture of the black hole we saw all over the news was a false color image, based on the radio spectrum emissions. How would the black hole at the center of M87 look like when ...
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4answers
7k views

What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

Would that person go blind? Neutrino detectors and the abundance of Neutrinos would detect the upcoming visible show about 3 hours before any visible signs, so there would be time to point certain ...
0
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1answer
177 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
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1answer
115 views

Verifying refractor lens about scratches

I found an used Skywatcher 70mm telescope for buying, but its lenses are a little suspect about harming. In one photo, it looks clearly a scratch, but in the another, it is not visible. Could it be an ...
2
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1answer
382 views

DSO in a 60mm telescope

I am thinking about buying a telescope, but here in Brazil they are very expensive and hard to find where to buy. So, the better telescope I can pay for is a Celestron Powerseeker 60AZ. My main ...
1
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1answer
312 views

Is moisture harmful to a Newtonian Reflector?

It is often cold outside, especially in the evening. So when I take my Newtonian Reflector back in my house, it starts condense. Can the water destroy my telescope? or the mirrors? Do I have to clean ...
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1answer
50 views

mirror image of the earth in the past [duplicate]

For example, if there was an object somewhere in the room, say 100 light years away, which would have to be very large and have the surface of a mirror, you could theoretically point the telescope at ...
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0answers
52 views

How to pick a telescope? [closed]

I am trying to find a started telescope for my high school sister and my goals are to have awesome pictures and to let her explore her interest in the stars! They live in a clear night sky area so Im ...
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2answers
2k views

Second Telescope: Maksutov Cassegrain vs Refractor

I bought my first telescope, a 3-inch refractor a few weeks ago. It has been a wonderful experience seeing the Moon, Jupiter, Saturn magnified and Andromeda, M33, M81 and much more for the first time. ...
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1answer
64 views

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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0answers
81 views

Methods for testing a refracting telescope lens

I have an old (nearly 50 years old)alt-azimuth three-inch (7.6cm) refracting telescope that someone else made. They ground the lens, created the cylindrical body and added a rack and pinion style ...
4
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1answer
133 views

What are the benefits of a large refracting telescope?

Currently, refractor telescopes are limited in aperture because gravity will deform the main lens over time. According to Wikipedia the largest practical refracting telescope is 1m. If we were to ...
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2answers
1k views

What (actually) is the “ deprojected half-light radius” of this almost-all-dark-matter Galaxy?

The recent news of the Ultra Diffuse Galaxy (UDG) Dragonfly 44 is an excellent example of what could be termed 'observe different' thinking. The dragonfly telescope is noted not for the size of its ...
3
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0answers
49 views

Is it possible to build a ground-based telescope that can directly image Earth-like planets orbiting in the habitable zone of sunlike stars?

In the following discussion I will refer to Earth-like exoplanets planets orbiting in the habitable zone of sunlike stars simply as “Earth-like exoplanets." NASA is currently developing or ...
3
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1answer
132 views

Would a 1000 km telescope be able to resolve microscopic detail?

I have calculated that a 100m telescope can resolve 16m on the moon. Does that mean a 1000km telescope is 10000x better and can resolve 1.6 mm objects on the moon and even smaller closer? Or is there ...
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0answers
31 views

How to determine Az-El pointing of a telescope spiral scan?

I am writing a simulation of an automated telescope observation program. One part of this is to run a spiral scan pattern on and around objects of interest. I would like to tile this scan pattern so ...
3
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1answer
62 views

Beneficial astronomical uses of satellite constellations like Starlink?

Has any thought been given to software that would use predictable occultations by Earth-orbiting satellites to improve (rather than degrade) astronomical observations? Potential challenges I could ...
4
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1answer
119 views

If we've only observed Oumuamua as a single pixel, how can we know its shape?

On a separate Oumuamua question (Oumuamua alien space junk?), I was confused how shape could be inferred from a single pixel, per another user's (@Uwe) comment. It was suggested I ask this question ...
3
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1answer
109 views

What are criteria to compare and evaluate different 12 inch truss Dobsonian telescopes?

What are criteria to compare and evaluate different 12 inch truss Dobsonian telescopes? I'm primarily interested in comparing mirror quality and weight (price I can do myself of course). Two examples ...
6
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3answers
2k views

Chromatic aberration in lens

Is there a way to prevent chromatic aberration without using an achromatic lens in refracting telescopes or in any other instruments...?
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0answers
98 views

Does it make more sense to upgrade our existing telescope or to buy a new one?

We're at a bit of a crossroads here, since we're faced with what appears to be a tough choice. We've got a Celestron 11" SCT tube with a Losmandy G11 equatorial mount, all bought in 1996. The mount ...
4
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1answer
526 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
98 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 ...
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2answers
266 views

What kind of telescope should I get my husband?

I'm very much an amateur when it comes to telescopes. My husband wants one for his birthday. I'm willing to spend up to $900 on one. Can any of you gurus give me advise as to which one I should buy? ...
3
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1answer
486 views

Is there any site with telescopes data?

Is the data gathered from telescopes "open source"? If so, is there any website that group it all?
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2answers
657 views

What soviet telescope is this?

A friend has a vintage telescope with a broken lens, I asked him to send me its catalog so I can see if I can buy him a new one, he gave me what looks like a Russian catalog, it seems a soviet ...
2
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1answer
318 views

Why is this telescope so short? How hard is it to make such a fast primary?

The recently discovered object C/2019 Q4 (Borisov) is in the news because it might have an eccentricity greater than one, which means it might be from outside the solar system, though not necessarily. ...
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2answers
2k views

I need help using this telescope!

The telescope I'm using is a National Geographic 76 Diameter, 700 focal length, Equatorial Mount. It's hard to use the equatorial mount, as this is my first telescope it's hard to use. Everything I ...
3
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2answers
140 views

How can I obtain raw observation data of stars surrounding Sgr A*?

Are there any publicly available telescope that offers the sensitivity to observe the stars surrounding Sgr A*? If not, is there any raw data available that I could download?
8
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1answer
838 views

How can I observe Sgr A* with itelescope.net

I've been experimenting with itelescope.net and tried to observe Sgr A*. I was wondering if there are any suggestions how I can best observe the surrounding stars.
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3answers
272 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
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1answer
106 views

What's the origin of Clyde Tombaugh's 9-inch Newtonian telescope?

Astronomer Clyde Tombaugh is shown in a now-famous photograph at the age of 24 with his "homemade" 9-inch Newtonian telescope in this image also shown in Elva R. O'Hara's Clyde W. Tombaugh: ...
5
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2answers
12k views

How many celestial bodies can I see with a 90x telescope?

I am a 9th class student so I'm a beginner at using a telescope, hence please help me. How many bodies can I see using a 90x telescope? How will I know when and where I should point a telescope to ...
2
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3answers
431 views

Meade ETX-90 with computerized mount slews too far during auto-alignment

I've been trying to get my new ETX-90 to properly align itself these past few nights, but without success. I've mostly been using the Easy align functionality, which has been choosing Arcturus and ...
2
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1answer
154 views

Difference between first (focal length (fl.) 500 mm, ocular (o.) 10 mm) and second telescope (fl. 1000 mm, o. 20 mm)? (both 50 x)

Magnification is defined as $f_{objectiv}/f_{ocular}$. If I had the first telescope with the focal length of 500 mm, ocular 10 mm and second telescope with the focal length of 1000 mm, ocular 20 mm, ...

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