Which is better, a refracting or a reflecting telescope?


by Sniperman724
Tags: reflecting, refracting, telescope
Sniperman724
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#1
Nov7-10, 04:37 PM
P: 66
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?
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jnorman
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#2
Nov8-10, 12:00 PM
P: 308
a refractor has no obstacles in the image path which can cause diffraction. reflectors have "spiders" (newtonians) and/or multiple optical elements which result in diffraction and lower respective image quality. both types have their advantages and disadvantages.

given any specific objective size, the refractor design is generally more expensive, and at a certain point (about 40"), refractors become infeasible due to the weight of the primary objective lens and the length of the tube. reflectors can, these days, be built to any dimension via multiple objective mirrors all controlled by computer to perfect alignment (well, within a reasonable degree of accuracy at least).

refractors are generally considered to be the instrument of choice for planetary viewing due to the pureness of the image path. reflectors are the instrument of choice for deep space and wide field viewing, due to the affordability of superior light gathering power of large mirrors vs smaller objective lenses for a given cost. a large folded reflector is far more portable than a large refractor, as well as more affordable.

so a determination of "which is better?" becomes dependent on what type of viewing you wish to do, how portable the system needs to be, and what your budget is.
turbo
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#3
Nov8-10, 12:39 PM
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Quote Quote by Sniperman724 View Post
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?
You are asking a question fraught with potential misunderstandings and more questions. If you have been looking at the literature, you might think that RC optical tube assemblies are the cat's meow because their hyperbolically-figured primary and secondary mirrors do a good job minimizing coma. Plus, the manufacturers all tell you that the really nice, big professional telescopes tend to be RC designs. What they don't tell you is that for amateurs, a REALLY nice apochromatic refractor with no central obstruction can be a lot cheaper, and provide detailed views, even at smaller apertures. They also don't tell you that mechanical limitations restrict the really big telescopes to reflecting designs - a limitation that you don't face as an amateur. There are some pretty big truss-style Dobsonians out there, but I'm pretty happy with my 6" refractor. When skies are steady, planetary views are stunning, and when they are not, it's still good fun to chase the faint fuzzies.


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