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Re: RE: RE: Upgrading From Meade 4.5

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Posted by Art Brown on November 4, 2000 15:43:46 UTC

Resolution and Definition.

These qualitites determine the sharpness of a telescopic image. Resolution is the ability to separate or resolve two adjacent point images. Definition is the clarity of extended images. Extended images include the surface of the moon, planets, etc. All stars are point images.

Resolution depends on aperture. The only way to improve resolution is to increase the aperature of the telescope. If you double the size of your telscope lens or mirror, you improve resolution twofold.

Definition depends to some extent on resolution, but also on the overall quality of the optics.

Also, there are limits to a telescopes capacity for magnification. The upper limit depends mostly on aperature. If you magnify an image too much, it becomes fuzzy and/or to dim to see. The general rule for extimating a telescopes upper limit of magnification is 60x per inch of aperature. Therefore a 2" telescope basically has an upper limit of magnification of 120x, a 6" is 360x, 8" 480x, etc.

A lot of factors enter into how much magnification you can find useful at any given time, such as air turbulence, quality of optics, etc.

Deciding on what size telescope to purchase involves a lot of factors such as portability, cost, where you will use it, etc. The best telescope you can buy, is the one that you will use. There are a lot of big scopes sitting in closets because they are to big to handle easily.

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