how does the length of a refractor affect the resolution and light-gathering ability of the telescope?
409559
The light gathering power and resolution are determined by the size of the objective lens, but not of its focal length. The ease of going to higher powers is determined by focal length.
169706
the angle between the incident ray and the perpendicular to the reflecting or refracting surface at the point of incidence
492923
The eye it not limited by distance;\n\nit responds to photons hitting the retina, it does not care how far the photons have travelled.\neg you can see a bright star further away than a dim one because it emits more photons. A telescope serves to collect more photons.\nIn a dark room you cannot see even close objects.
166306
You need to know the focal length of the eyepiece as well.  The magnification is the ratio of these focal lengths; e.g., 48 if you have a 1 cm eyepiece.  The apparent distance is the actual distance divided by the magnification.
138088
The hubble telescope it up above all the atmospheric disturbance, allowing for much higher quality photos.\n\nFor the same reason stars twinkle, land based telescopes have a limited resolution power, after a certain size, it doesnt really help any (unless you want to build a complicated atmospheric correction machine to adjust the mirror to compensate).
126059
Magnifying mirrors are concaved inward and work by focusing the light on a point such that the image is larger than the original object.\n\nhttp://physics.bu.edu/py106/notes/Spherical.html
254369
Ahhhhhhh...A fledgling Amateur Astronomer!!...WONDERFUL!!\n\nThe first and foremost thing to consider is APERTURE..This is the SIZE of the opening of the telescope...The reason is, except for the moon, astro objects are dim...the larger the aperture, the more LIGHT will be gathered and focused into your eyepiece, so the clearer the image and the higher magnification you can use without blurring.\n\nYou mention a price range of $2000...That much money will buy a GREAT telescope, however, I suggest you start with a less expensive Dobsonian telescope for your first purchase.\nThis will give you some experience, HOURS of enjoyment, and will let you see if you are REALLY interested enough to upgrade to a more expensive piece. Dobsonians ( or NEWTONIAN...Same principle, REFLECTORS ) of good quality can be purchased on E-bay for around $300-$500.\n\nIn the $2000 range, look for a 'Schmitt-Cassegrain' with ' Go-To' electronics...Readily available
901312
b) is the correct answer, as others have said. You know, telescopes are a lot easier to understand if you look at a diagram.\n\nYou can find some here: http://en.wikipedia.org/wiki/Reflector_telescope
982426
That depends what consideration you have.  Reflecting have the advantage of having less chromatic aberration than refractor, and tend to be larger for a given weight.  The most important aspect for a telescope is the size of the primary mirror, because it defines the light gathering capability, so this is a case where bigger is better (as long as the quality is there, evidently)\nCassegrain is a variation of the reflector, where a secondary mirror sends the light back through the center of the primary; the other style is Newtonian where a diagonal mirror sends the light t the side.  For moderate size telescope Newtonian is more comfortable.\nA very important aspect to consider is also the mounting.  If you only want to do optical observation, then a Dobsnian mounting is very cheap, as it forgoes the tracking mechanism.  If you would want to do astophotography with long exposure, then you would need an equatorial mount with a drive that can track a star.  Recent models rely on computerized motorization, which as most electronics, have allowed the advanced capabilities for an relatively acceptable price.\nMy suggestion is that you document yourself, perhaps buy a couple of issues of astronomy magazine, like Astronomy or Star & Telescope, and get acquinted with the market.  You will be able to decide what you want, and what you can afford.\nAnd I hope you have access to clear sky and dark night.\nHappy observations!
567526
The same reason why a pinhole camera works.  As light passes therough the pinhole, it refracts and is focused.
140884
The only disadvantage of the telescope is cost.  The fact that they need motors to track stars is a cost factor.  The field of view degredation with magnification can be compensated for with high cost eyepieces.  The fact that they can only see light that penetrates the atmosphere isn't a disadvantage because we can't see that anyway.  There are disadvantages to different types of telescopes.  Some of the catadioptric scopes do not have as wide a contrast range on the Moon and planets as a refractor.  Refractors suffer from chromatic aberration (or "spurious color"). This is an optical defect that produces a faint pale violet halo around bright stars, the limb of the Moon, and the planets.  Reflectors, because of the parabolic shape of their primary mirrors, all have coma – an optical defect in which stars appear triangular or wedge-shaped at the edge of the field. Where as Dobsonian Reflectors give you the best aperature for your money, there size and maintenance (collimation) are considered by some as drawbacks.
491826
Pretty much any telescope will see 'to' Uranus. Occasionally it can even be seen without any optical aid. That said, do not expect to see more than a small blue dot, even with a fairly big scope (one past what you are willing to pay).\n\nGenerally speaking, refractors are better for planetary viewing because they allow a higher magnification (longer focal length). The problem is that they are subject to chromatic abberation (little rainbows around bright objects) unless you spend a lot to correct it with good quality lenses. Reflectors will more often have spherical abberation, which tends to blur out features, so they tend not to be as good for planets.\n\nNext, are you talking about just the telescope or is the $600 for the telescope AND eyepieces? The right eyepieces can make a huge difference, so don't neglect them when shopping. For planets, get a couple of medium to high power Plossl eyepieces.\n\nBelow is a site with some good refractors. Disclaimer: I am not in any way affiliated with Orion Telescopes.
1049049
The Focal Length (distance from the Focal Point to the lens) is VERY different.  The Focal Point of a Telescope may be very far away.  But the Focal Point of a Microscope may be only a fraction of an inch away.\n\nAlso, the Telescope has a much larger aperature (lens diameter) to allow it to capture the tiny amount of natural light at the Focal Point.  A microscope usually illuminates the Focal Point with artificial illumination.\n\nHere's a good discussion of Focal Point and Focal Length:
64464
It's nearsightedness.  The convex lens formed by the eye's own lens and the curvature at the front of the eyeball determines the focal length.  A concave lens corrects the problem by increasing the focal length.
417677
For refractors, the most common problem is chromatic aberration. In this, you get little rainbows around bright objects and a blurrier image around others. This happens because the lenses act like prisms. All refractors are subject to this, but some *very* expensive ones have it less. They fix this by using more than one type of glass.\n\nFor reflectors, the main problem is spherical aberration. This is caused by the mirror not being a perfect paraboloid. It is much easier to grind a sphere than a paraboloid, and most mirrors are first ground to a spherical shape. If the subsequent grinding isn't done right, the resulting images will be blurrier than need be. For decent images, the mirror's shape has to be within 1/4 of a wavelength of light, and for a good image it should be correct to within 1/10 of a wavelength. Considering how small the wavelength of visible light is, you can see how hard that is.
474015
As the focal length was not mentioned it's impossible to measure the distance between primary mirror and diagonal. I calculated that it should be more than a meter if the f ratio is high enough.\nI don't need be an Indian to see Indian movies. DVDs are released worldwide. However, I am neither from S.P.A.C.E nor from Galileo. I run an astronomy organization myself. I'm associated with many other international organizations.
394180
It has to do with refraction due to different densities of air-in cooler climates, there tends to be much warmer air near the surface, with colder air in higher altitudes, plus the colder air is much more dense, so acts like a magnifying lense- The very largest moon-views are always seen close to the horizon because of this.