What is Telescope: Definition and 513 Discussions

A telescope is an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. The first known practical telescopes were refracting telescopes invented in the Netherlands at the beginning of the 17th century, by using glass lenses. They were used for both terrestrial applications and astronomy.
The reflecting telescope, which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.

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  1. O

    Stargazing Most powerful telescope system of the future?

    What do you suppose would be the limiting resolving power of this telescope system? Assume it's built on Earth or nearby with money no object. Could it, for instance, detect a butterfly flitting about on a planet 100 LY from us? If not, what are the limiting factors? Thanks!
  2. 1

    Stargazing What's a good, affordable telescope for someone who's never owned one

    What's a good, affordable telescope for someone who's never owned one, and just likes the sky?
  3. B

    Destructive Interference: radio telescope, ocean, galaxy

    Homework Statement My solution isn't working out for this question. Radio waves of wavelength 125 m from a galaxy reach a radio telescope by two separate paths. One is a direct path to the receiver, which is situated on the edge of a tall cliff by the ocean, and the second is by...
  4. W

    Radio telescope parabola question

    If a particular radio telescope is 100ft in diameter and has a cross section modeled by the equation x^2=167y, how deep is the parabolic dish? What is the location of the focus? can someone show me some steps to solving this? I have (167/4,0) as the focus for the second part but I am not...
  5. Ryan_m_b

    Stargazing Telescope Limitations: What to Know

    Hi there, I was reading a novel recently where a character was using telescopes to watch vehicles moving on a planet at many light hours distant. The 'explanation' for his telescopes awesomeness is that it is designed to see distant stars and so seeing people moving on a planet in the same...
  6. D

    Optical Telescope Set-Up: Objective & Eyepiece Combination

    I am trying to prepare a telescope with the following lens combination. Can someone suggest if it is any good? :confused: I am intending to notice the planets and the moon in detail. Objective: Plano convex - 50cm focal length Eye-piece: The lens supplier suggested I use a Ramsden's...
  7. DaveC426913

    Stargazing When was the first telescope used to view the stars?

    Many stories (including most internet accountings) tell of Galileo using the first telescope to look a the stars in 1609. Some reports suggest it was used earlier. What is the accepted truth re: first use of a telescope to view the stars?
  8. D

    Stargazing Pleasure of owning a telescope a telescope

    i think everyone should have the pleasure of owning a telescope a telescope can clearly put a lot of things into perspective
  9. U

    Stargazing Objects Visible with Telescope & CCD Camera - Focal Length 100 cm

    How to determine the obejcts that are possible to be captured with a telescope ( focal length 100 cm, lense diameter 10 cm) and a CCD camera (matrix: 1530x1020 pixels and the length of each pixel 9x9 nanometers). For example the objects could be the moon, Mars, Andromeda galaxy... And what would...
  10. Drakkith

    Stargazing Mastering Telescope Collimation: Tips and Tricks for Perfect Alignment

    Hello! I purchased a 130 mm reflecting telescope a few months ago. I recently have had to try to collimate it due to the mirrors being out of alignment, but I'm not sure I'm getting it 100% correct. I follow the directions in the instruction manual, but it seems that even when I think it's...
  11. S

    Stargazing OECSYAZ2D114/F900 Telescope Help.

    I have recently received a OECSYAZ2D114/F900 Telescope. It appears to be set up correctly, however when I look through it, I cannot see a thing at all! I really need some help, as I can't find a website that assists in this matter. :confused:
  12. Z

    Stargazing How to estimate distance by a telescope

    Guys I don't know if people could estimate distance to a target object by looking through a telescope. I believe telescopes for this kind use must be calibrated some how. When the time people sailed in the ocean and when they spotted another boat by the telescope, how did they tell the...
  13. A

    Astronomical telescope refraction problem, an easy one

    Homework Statement 1.a) Design an astronomical telescope with an angular magnification of +5 (pay attention to + sign !) and length of 16 cm, i.e. compute fobjective and focular). Homework Equations M=-(f_objective/f_ocular) L=f_ocular+f_objective The Attempt at a Solution...
  14. nukeman

    Stargazing What features of Andromeda Galaxy can you make out with an Amateur Telescope?

    What features of Andromeda Galaxy can you make out with an Amateur Telescope?? With an amateur telescope, (field of view of 2 degrees) what features can see you see in and around the andromeda galaxy? Just curious.
  15. B

    NASA NASA'S Fermi Telescope Discovers Giant Structure In Our Galaxy

    Sorry if someone already posted this link but did anyone see this in the news? http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-295_FERMI.html What are people's opinions on what this might be?
  16. S

    Stargazing Which is better, a refracting or a reflecting telescope?

    I just thought I would ask on this forum because I was curious to see how the experts in the field feel about each type of telescope. I understand a reflecting telescope can be more compact than a refracting telescope, but are there any advantages or disadvantages to one over the other?
  17. nukeman

    Stargazing Looking for images of same object, but with different telescope sizes?

    Hey guys, Iv been looking for this, but can't seem to put it together. Mainly I am looking for images of the same object, like Jupiter or andromeda, with various sizes of telescopes, showing the difference in image of small telescopes to large ones. Like, a small dob, to a 6, to a 8...
  18. S

    Exploring the Resolving Power of Green Bank's 300-ft Telescope

    Question: Before it collapsed in 1989, Green Bank's 300-foot diameter telescope mapped the sky in H I. What was its resolving power? I believe the formula you would use is resolving power = (wavelength in microns) / (diameter in meters) So the diameter in meters would be about 91.44 m, but...
  19. L

    Stargazing Best Telescope Under $400: Top Picks and Recommendations for US Shoppers

    with about 400$, any suggestion for me ? what i should buy, pls me a store or brand in US pls :D
  20. I

    Stargazing Increasing the resolving power of a telescope

    I have a toy telescope, very poor objective aperture like 30mm, the image is very poor. I was wondering if I could increase it's resolving power by placing a convex lens with a larger aperture in front of the objective lens? The larger lens should converge more light rays onto the...
  21. K

    Stargazing Pictures I took at a 2.5m telescope in the Canary Islands

    Hi there, physics nerds! I'm studying astrophysics in Copenhagen, and I had the opportunity to visit a telescope in the Canary Islands (just off the west coast of Africa). It's called the Nordic Optical Telescope, and I was there for a week in August. Among other things, I managed to get 4...
  22. N

    Stargazing Heyy, i've had a telescope before and know how to use them.Has

    Heyy, I've had a telescope before and know how to use them. Has anyone got any advice on a second model that I could get for my second telescope. Between the price range of £100-£200. thanks guys :P
  23. N

    Stargazing Telescope in range of £100-£250

    Can anyone guve any idea of a good model telescope to get? I've had previous telescopees, but I am now lookign for something that is as good as you can get from the range of £100-£250. Thanks Guys :-)
  24. P

    Stargazing What is the Best Catadioptric Telescope for Portability and Versatility?

    I am in New Mexico and currently planning a telescope purchase but quite confused with all that is available. Seeking a catadioptric, 6" size and currently looking at Celestron NexStar 6 SE and Meade LS 6 ACF. I selected these for their ease of portability, as well as their convenience of use...
  25. T

    Plotting Intensity in Airy Pattern of Telescope - 1D

    How would I come up with an equation (in one dimention), for the airy pattern of a telescope with a given diameter observing at a given wavelength? something that looks like this http://upload.wikimedia.org/wikipedia/commons/9/93/Airy_Pattern.svg I want to be able to plot Intensity in the...
  26. H

    Stargazing Which Telescope is Best for Viewing Planets and Nebulae on a Budget in Wales?

    I live in Wales, UK, I am doing my GCSE's now and I am really interested in astronomy, I've asked my parents for a telescope for my birthday in december, I am looking for one around £80-£120, i want one that can see planets like jupiter, saturn and maybe star constellations, galaxies or nebulae...
  27. M

    Stargazing Trying to pick out a telescope (Need help)

    I'm an Astronomy major with an emphasis in Astrophysics. So my career is going to be in studying the sky and deep space objects. I have owned several telescopes in the past but never really learned how to use an equatorial mount (I was about about 8 years old at the time and didn't have the...
  28. J

    Stargazing Best compromise for portable telescope?

    so, for best resolving power, the objective lens of a telescope needs to be as large as possible, and have the fewest optical elements. for portability, the physical size and weight of the system needs to be as small as possible. within these two disparate parameters, what do you consider the...
  29. E

    Optical Better DIY planetary telescope: 8 or 6

    better DIY planetary telescope: 8" or 6" Hey all, I'm starting to design my first home built telescope. I already own a 10" dob which works great but I've decided I would like something more transportable that is easier to take camping or wherever else. So right now I'm leaning towards a 6 or...
  30. C

    Stargazing Exploring the EPR Sky: Detecting Matter Beyond Our Visible Universe

    Suppose that we focus our optical or radio telescope on a star or galaxy R light years away. If we continually measure the polarity of the photons received and continually get definite results, then we know that at the location 2R from us, the location is empty of matter; ie, no detection...
  31. Chronos

    Stargazing My Telescope Adventure: Meade LXD75 SN10

    I recently acquired a Meade LXD75 SN10 telescope [Schmidt-Newtonian]. It has been an adventure. It is big, heavy, awkward, etc. I only have to lug the beast about 15' to set it up, so despite my age and feebleness I can manage the task in about 15 minutes. I thus far have made the following...
  32. russ_watters

    Stargazing How big of a difference have you noticed with cooling your telescope mirror?

    Anyone have any experience with cooling a telescope mirror for image quality improvement? I have my C11 disassembled for some other upgrades and before putting it back together am considering adding a cooling fan. Anyone have opinions on how big of a difference it can make?
  33. P

    Fermi Gamma Ray Telescope: Ruling Out Lorentz-Violating Theories

    The almost simultaneous detection of low energy and high energy photons puts tight constraints on models predicting linear dependence of c on E. But it's very far from ruling out quadratic dependence. My question is, why do Lorentz-violating theories commonly predict linear rather than quadratic...
  34. cronxeh

    Stargazing Need advice on telescope for astrophotography

    So I am finally getting out in the wilderness on vacation and I thought it would be a great idea to do some astrophotography. I thought of getting a simple enough Nextstar 4SE, but I have a bigger budget and maybe I can get a bigger diameter and aperture. So my question is, which telescope...
  35. A

    Calculating Angular Size of Moon with Telescope

    Homework Statement The moon is observed using a telescope that has an objective lens with a focal length of 3.0 m and an eyepiece with a focal length of 7.5 cm. What is the angular diameter of the moon if the earth-moon distance is 3.85 × 108 m and the diameter of the moon is 3.48 × 106 m...
  36. L

    Stargazing Oops, I didn't read the post good enough, sorry!Last edited: Oct 30, 2016

    I have a question that I could really use some help mathematically on. At its closest to Earth, Pluto is 28.6 AU from Earth. Can the Hubble Space Telescope distringuish any features on Pluto? Justify your answers using calculations. Please help! I know that the diameter of Pluto is...
  37. C

    Stargazing Mars' orbital telescope and ice rock

    Might one place a telescope in Mars orbit, in order to obtain 6" to 1 ft resolution, looking for closeup geological views; such as mars' stromatolytic fossils, or mars' ice (rock) on the surface, in form of a smooth surface that seems a bit odd? Might billions year old Mars' ice be opaque to...
  38. Z

    Stargazing Telescope size and wavelengths

    I have been reading an article that refers to telescopes but I don’t really understand telescope sizes; http://www.eso.org/public/news/eso0226/ For instance take the 3.5-m New Technology Telescope. I assume that the 3.5m refers to the diameter of the parabolic mirror. Does the 3.5m...
  39. B

    Design a Telescope Optics for Spy Satellite- Angular Resolution & Mirror Size

    Homework Statement This is a question on my final review. Imagine you are given the task of designing the telescope in a spy satellite that is going to be launched into an orbit 500 km above the surface of the Earth. The agency you are working for wants to be able to clearly see objects...
  40. Z

    Stargazing What are the Limits of Wavelength Detection in Modern Telescopes?

    What are the longest wavelengths that todays telescopes can detect for?
  41. r.vittalkiran

    Stargazing Galilean Telescope: Taking Photos with Digital Camera

    I have an Galilean telescope with me...with 1Ox EYEPIECE and 100cm Focal lengthlens at the other end... I can see the craters of the moon properly with it, i require to take a snap of it using my digital camera... but not able to get a proper image in camera. What can i do? any Idea?
  42. P

    Stargazing Suggesting a beginners telescope

    Can you recommend me the telescope for beginners Is Skywatcher Heritage 76 mm is good for beginners thank you
  43. S

    Find resolution and size of telescope dish.

    Homework Statement From the shape of the Sun’s emission in the plot, estimate the resolu- tion of the telescope (the full width half maximum of the Gaussian shape) and from this calculate the size of the dish. The sharp bell represents the sun's emission and hydrogen is used as the...
  44. S

    Solar/Sidereal day/SpiralArm/Orbital Speed With Radio Telescope

    Homework Statement Hello, I have 48-hour data from a radio telescope on Earth, and my goal is to answer these four questions: 1) Calculate the length of a solar day. 2) Calculate the length of a sidereal day 3) Explain how to locate a spiral arm on one of your plots and how to determine its...
  45. C

    Managing Telescope Aiming: a Sky-Watcher Challenge

    ..sucks. I have the Sky-Watcher 10" dob (got it for xmas). All around, it's a great scope for the cost, and produces some very crisp visuals of surprisingly distant objects... when it can center on them. I find myself having to constantly aim higher than the object so my telescope will "fall"...
  46. MotoH

    Stargazing Celestron Astromaster 114EQ Reflecting Telescope: A Beginner's Guide

    I am starting to get into looking at far off objects in space, and have decided to purchase a reflecting telescope. I am looking at a Celestron Astromaster 114eq. http://www.telescopes.com/telescopes/reflecting-telescopes/celestronpackageastromaster114eqreflectortelescope.cfm" The explorer...
  47. T

    Stargazing Could a very large telescope see a star as a disk?

    Hi When I was a kid, the largest telescope was Mt Palomar, a little over 5 meter diameter mirror. In spite of its large size, I always read that stars appeared as points of light through the scope if it were used visually, i.e. stars are too small and too distant to appear as disks. However...
  48. T

    Stargazing Buy Telescope: Tips for Amateurs

    Hi guys! I am planning to buy a telescope for a descent price. You see I'm totally amature and buying this telescope would be my first telescope itself. I sure have observed the night sky with binoculars and home made kinda simple telescopes but now I want to switch to something better. So...
  49. W

    Stargazing Building Telescope Signting Laser

    Hello! I recently purchased a basic 6-inch Equatorial Reflector telescope. I bought it because I loved doing astronomy with large binoculars, and I assumed the next step was a small reflector telescope. However, I find myself barely using the new scope because the bulky Equatorial mount is...
  50. S

    Stargazing Amateur telescope eyepiece filters

    So, I have a relatively small (6") Orion Dobsonian with a 25mm and 7.5mm Plossl eyepieces and live in a somewhat light polluted area. Because of this, I am considering purchasing an eyepiece filter to reduce light pollution and enhance nebula/planetary viewing. I was wondering how this would...
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