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. S

    Stargazing Telescope Advice: 6" vs 8" Dobsonian

    Hi I had posted here for some advice a couple of months ago in the past, and it was very helpful. I have yet to buy a scope; however, I am on the presently on the verge and wanted a little more advice. I have basically come down to a decision that I will bet getting one of two dobsonian...
  2. vincentm

    Stargazing Building a telescope ( from another one )

    Hello, I'm looking to build my first telescope from http://www.apogeeinc.com/product.asp?itemid=766 (PDF file). My question is this, is this a suitable guide in doing so? If not what steps should i take to successfully complete this task?
  3. D

    Stargazing Discover the Wonders of the Night Sky with WorldWide Telescope

    So what do you guys think of this software? Do you use it often? Like it? Hate it? By some strange chance haven't heard of it or downloaded it? Here's a link to the website: http://www.worldwidetelescope.org/ I was astronomically challenged before using the software, but it's been...
  4. W

    Hubble Space Telescope Orbital Period

    Use Kepler’s laws to determine the period of the Hubble Space Telescope which orbits the Earth at an altitude of 610 km. I'm using the equation i know to find the period of an object revolving around another object T^2=Kr^3 T^2=(4pi^2/GM)*r^3 G=6.67 x 10^-11 M=5.98× 10^24 (Mass of...
  5. D

    Building a Telescope for Physics Class: Choosing Lenses & Mirrors

    Hi, I need to build a telescope for my physics class. I need to use any 3 lenses(converging or diverging) and 1 mirror. I was thinking of using an achromatic telescope design for that. However I am not sure what kind of lenses to use and whether I should make the eyepiece from two lenses or just...
  6. S

    What is the Worldwide Telescope Project and how does it compare to Google Sky?

    Microsoft is launching a new online virtual telescope project called Worldwide Telescope. It is an evolutionary step above Google Sky, and is located at http://www.worldwidetelescope.org. Both Google Sky and Worldwide Telescope have great potential for exploration and education in astronomy...
  7. S

    Stargazing Telescope Advice: Get Good Views for a Cheap Price

    Hey everyone, I am thinking about buying my first scope and I am not really sure what I should be looking for and what a good deal is. I am trying to get a decent scope for not much money; I would not like to spend over 350. However if you could get significantly better images with a little...
  8. F

    Calculating Angle of Saturn from Earth Using a Refracting Telescope

    Homework Statement Saturn is viewed through the Lick Observatory refracting telescope (objective focal length 18 m). If the diameter of the image produced by the objective is 1.7 mm, what angle does Saturn subtend when viewed from earth? Homework Equations \theta = -y'/f1, where...
  9. B

    What is the approximate focal length for a 10X telescope with a 20 cm length?

    Test TOMORROW PLEASE HELP ME! Telescope! Homework Statement I need serious help! I have a test tomorrow and I am having trouble with microscope/telescope questions... A person is designing a 10X telescope is limited to a length of 20 cm, what is the approximate focal length of the...
  10. Saladsamurai

    Stargazing Telescope alteration (Russ or turbo-1)

    I'll take any information, I just know that Russ and Turbo have helped me before. Okay, here is the rundown: I have a really inexpensive ($150) Meade reflector telescope. Here are the specs: 114 mm primary, F=1000mm, f/8.8 I am not quite sure what the F=1000mm, f/8.8 means. Now...
  11. W

    Telescope Resolution for AGN Accretion Disk

    [SOLVED] Telescope Resolution Homework Statement An Active Galactic Nucleus (AGN) is fueled by gas and dust in a rotating accretion disk that is streaming onto a supermassive black hole in the center of the galaxy. These accretion disks are typically a few pc in diameter and are best detected...
  12. M

    Stargazing Finding the Perfect Telescope: A Guide for First-Time Buyers

    I Am Looking At A Meade Ds-2130at Goto I Don't Know Anything About Telescopes It Will Be My First Please Help If This Is Not A Good One What Should I Look For
  13. X

    Solve Antique Telescope Homework: Find Fe Focal Length

    Homework Statement On one of the shelves in your physics lab is displayed an antique telescope. A sign underneath the instrument says that the telescope has a magnification of 20 and consists of two converging lenses, the objective and the eyepiece, fixed at either end of a tube 60.0 cm...
  14. P

    Stargazing Why Do Telescopes Have Long Focal Lengths?

    Hi all, Do you know why the lense (or mirror) of telescope often requires that the focal lengh be rather long? What is different between a backyard telescope and a normal camera? Thanx.
  15. T

    Stargazing Buying a Telescope , guide me.

    hi i am completely naive when it comes to astronomy, telescopes and all that stuff. I'm looking forward to buy a telescope. What would you suggest ? I'd like to keep it under 150$. oh and ya, i just got a copy of "deepsky astronomy software" ! so i'd like to get a telescope that's compatible...
  16. Y

    Stargazing Viewing Saturn from a 6 telescope

    Viewing Saturn from a 6" telescope Hello I am not quite sure what resolution i am suppose to see if i look through saturn in my Orion 6" Newtonian reflector at 300X. Can anyone show me a picture of saturn from a 6" telescope that is not editted? Thank You Scott
  17. E

    Stargazing Can we see human history through a telescope?

    In the same way every time we look at the stars we see the past of the universe. Can we see our history placing a extremely powerful telescope pointing towards the Earth an arbitrary number of light years away? I know that would require faster than light travel, but maybe we could shortcut...
  18. J

    Stargazing Can i use a watch glass as a primary mirror of dobsonian telescope?

    can i use a watch glass as a primary mirror of dobsonian telescope?
  19. J

    Stargazing Magnification of dobsonian telescope

    how can i get the magnification of dobsonian telescope i made??
  20. J

    Stargazing Primary mirror for dobsonian telescope

    can i use a concave aluminum mirror as an objective mirror of a dobsonian telescope??
  21. Y

    Stargazing Optic Quality and Useful Magnification of the Orion Skyview Pro 6 Telescope

    Hi I am slightly confused... Many books and website says that your telescope's useful magnification ranges from 20X per inch to 100X per inch according to the optic quality. How do i find out the optic quality and useful magnification for my own telescope? (p.s. i am using a Orion Skyview Pro 6")
  22. E

    Stargazing Want to run out and buy a better telescope

    Man you guys make me want to run out and buy a better telescope. Don't laugh, but I thought I was doing good with a Baytronix Newtonian. (You know the ones on ebay for a few hundred bux) I regret it now, I didn't know any better back then. What would you recommend for a budget of around...
  23. J

    Stargazing Objective mirrors for telescope

    is there anyone know how to make a parabolic mirror at home?
  24. Y

    Stargazing What kind of telescope to buy?

    I am very new to this forum and even to any astronomy discussion. I have been just fascinated by it and always wanted to learn more. Just never got time. But now I feel I have to manage time otherwise I will never be able to. Anyways, I want to buy a telescope. How should I go about it. I am...
  25. G

    Stargazing Meade 10" Starfinder EQ Telescope - Buy Now on eBay

    http://cgi.ebay.com/MEADE-10-STARFINDER-EQUATORIAL-TELESCOPE_W0QQitemZ250200702977QQihZ015QQcategoryZ28181QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Is this a good deal? I'm not too familiar with older telescope models such as Starfinder... now if only that was a LX200R for $350 :(
  26. P

    Noise Removal in Radio Telescope Observations

    while dealing with radio telescopes how can we remove the noise and other disturbances like microwave radiation etc.
  27. B

    Stargazing Telescope and astronomy questions

    My friend has a telescope that I think is controlled with a motor. Does this kind of telescope have to be hooked up to a computer or something. Were going out to look at Mars and I don't really know anything about setting up telescopes or anything. What kind of computer program would I need...
  28. W

    Stargazing Question on Refractor Telescope

    I am plan on building a small refractor telescope about 20 cm long, i need your guys help ! 1. What len is use for Objective len and what len is use for Eyepiece len ? (how is it look like) 2. How far should i place objective len and eyepiece len apart ? 3. If i make a 20 cm long refractor...
  29. A

    Stargazing How to make a telescope using simple steps?

    How to make a telescope using simple steps?
  30. R

    Stargazing Why isn't the magnification of a telescope (-)

    I was wondering why the magnification of a telescope is not considered negative since it is inverted. I know it doesn't really matter much since all you are trying to do is get a larger image but the sign convention should still be followed I think. The book I am using is Giancoli Physics for...
  31. S

    How Is the Focal Length of an Ocular Determined in an Astronomical Telescope?

    A Huygens ocular is constructed of two thin lenses of focal lengths 10cm and 5cm respectively, separated by 7.5cm. The ocular is used in an astronomical telescope whose objective is 30cm to the left of the front lens of the ocular. I need to find the position of the exit pupil, and then find...
  32. S

    Stargazing Solid angle acceptance of a muon telescope

    I am trying to work out the solid angle acceptance of a muon telescope. The telescope is comprised of two aligned square detector panels (of size x squared metres) set at a distance apart of L metres. The way I was initially working it out (by using the solid angle of a pyramid of base x...
  33. A

    Stargazing Looking for advice on telescope

    I'm looking to buy a telescope for casual viewing of planets and galaxies. One I saw is an 8inch *1000mm focal length reflector type on a motorised equatorial mount with an 8*50 finder scope. Does this sound like something suitable for seeing a decent amount of lunar surface detail and the rings...
  34. M

    Stargazing Non-Magnifying Telescope Lenses: Components & Effects

    The components of a telescope are essentially two convex lenses? Out of curiosity (boredom) I am trying to figure out if the addition of another lens could make the image non-magnified. For instance, what type of lens/other would you add in order to make the image look as if you were...
  35. P

    Stargazing Check the profile of a telescope mirror

    Hi all, I know some men, who are amater astronomers. They made themseves reflective telescopes which can see the crescent Venus and many others in the sky. They say they make the mirrors parapolic shape although the depth of the mirror is very thin (about 1 - 2 mm). The diameters are often...
  36. G

    Stargazing Build a Powerful Telescope at Home | Tips and Tricks for Optimal Magnification

    Please say me how...telescope I want to make a telescope with the magnification of more than 20 times. I want to make it in my own home. I tried to make one using two convex lenses one og focal length 100cm(objective) and other of focal length 10cm(eye piece). So according to theoritical...
  37. W

    Stargazing What beginner telescope should I buy for under $150?

    Hello everyone. Giant astronomy newb here. Some background: My sons 5th birthday was a few weeks ago and I told my wife I wanted to get him a telescope about a week or so before. I did some research and basically got the "dont buy at a department store" message. My wife however was out...
  38. E

    Optics - Diameter of moon viewed through telescope

    Homework Statement I've been stuck on this problem for a while now, and have tried it several different ways, but with no results. I'm sure I'm missing something obvious or simply approaching it from the wrong direction. The moon subtends an angle of 0.5 degrees at the objective lens of a...
  39. Saladsamurai

    Stargazing I Am Cursed Ack Fi My New Telescope hates me

    Step 1:take telescope out of box and assemble according to instructions. 2. Install Crayford focuser. 3. Collimate to the best of my ability/knowledge 4. Take scope outside and point at Jupiter 5. Become enfuriated because for the 2nd night in a row, all I have been able to see is a...
  40. J

    Stargazing Liquid Mirror Telescope: How to create a parabolic shape

    I recently read about a proposed liquid mirror telescope to be constructed on the moon. My question is one of mechanics, hence this not being in the astronomy section. My question is regarding the shape of the surface of a rotating liquid. The design will have a dish containing a thin layer...
  41. Saladsamurai

    Stargazing Finally Ordering New Telescope

    I have been talking on this forum with some folks about telescopes and it seems that this is where I have been getting the best info. I have been looking to purchase a new scope for a couple of months now. After some research, it seems that buying something under $400 is almost garaunteed to...
  42. Astronuc

    Stargazing Great Canary Telescope - First Light

    AP News Tests begin on Canaries telescope http://news.bbc.co.uk/2/hi/science/nature/6897293.stm
  43. Saladsamurai

    Stargazing About Parabolic Telescope Mirrors

    I have been looking through websites with the intent to build a telescope. I have been looking at mirrors today and there are many to choose from including prefabricated ones which I will use for my first scope. But my question is with regards to the the other non prefabricated glass...
  44. Saladsamurai

    Stargazing What can I get to improve telescope

    Hey there, I am new to this particular forum. I recently picked up a Meade starting level telescope (nothing electric). I caught a glimpse of my first planet last night and it was rad! I do not know which planet it was, but I assume it was Jupiter as it had some dots around it...they were...
  45. H

    Stargazing Refracting vs Reflecting Telescopes: Which is Easier to Build?

    (ah, sorry I was not 100% sure were i should post this in the homework help or here, =/) I am building a telescope for a physics project and was wondering if anyone would be willing to help. I'm not sure were to begin but i do know (or think that I know) that I should build a refracting...
  46. M

    Optimizing Telescope Lens Distance for Distant and Nearby Objects

    A telescope has lenses with focal lengths f1 = +25.7 cm and f2 = +5.5 cm. (a) What distance between the two lenses will allow the telescope to focus on an infinitely distant object and produce an infinitely distant image? (b) What distance between the lenses will allow the telescope to focus...
  47. S

    Telescope in Milikan Experiment

    Homework Statement Homework Equations My book mentions a telescope in order to measure velocities of electron.But does not explain why to use it?Plz. tell me why to use a Telescope?Thanks. The Attempt at a Solution
  48. Bob3141592

    Stargazing Leaving Telescope Out: Pros & Cons

    I have a C8 on a tripod that I don't use as much as I'd like. One thing is my proximity to Chicago (45 miles NW of the city - not quite far enough away). Also, as my yard is set up, it's a real pain to take it in and out of the house. I'm not ready to build a shed observatory around it, so I...
  49. S

    Stargazing High-Altitude Floating Space Telescope

    Would it be feasible/practical to construct a large floating space telescope that perhaps would be incorporated into the structure of a large dirigible, blimp or balloon. Or perhaps it would simply be carried aloft by the said buoyant platform? Has anyone ever before proposed the construction...
  50. A

    Cleaning a Cloudy Patch Inside Orion 120mm Telescope Lens

    I own an Orion 120mm f\5 600mm telescope . I bought it last year from Orion . I recently noticed a cloudy patch about 2in. round on the inside of the scope on the lens , it looks like condensation to me . I've always been careful when i bring the scope in the house fron the nights cold air and...
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