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M4lcs67

Another daft question from yours truly!!!!

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Hey fellas,

Mearly inquisitive, but what constitutes the maximum usable power of a given telescope/eyepiece combination (apart from the obvious blurred image). But what constitutes the maximum usable power? Why is this? Why can't you go up and up? What is the usual rule of thumb? For my scope for example. It has an apeture of 127mm and a focal length of 1500mm. If I tried to put a very high powered eyepiece into it why wouldn't it work (apart from the blurred image again)??????

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Hi Malc,

These two articles may help:

Starizona's Telescope Basics

Magnification

They are both based on rules of thumb at around 50-60x the diameter of your scope in inches - e.g. 6" reflector -> 300 - 360x max mag.

If you do a search on the internet there are more in-depth articles that give the physical concepts as to why these rules of thumb hold. But also remember - they are absolute max mags in perfect seeing conditions!

Clear Skies!

Jim

Edited by JimBobs63

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Partly to do with resolution of image not being much more than resolution of retina ??

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I find the optimum balance between detail, brightness and resolution comes at about x1 per mm on most nights. For my scope that's x235.

Quite a few nights I use x294 and on those very rare steady nights x392.

So although it's true larger scopes take more magnification, atmospheric conditions won't allow you to get anywhere near on most nights.

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As to why the image degrades beyond a certain power, I can only think that you are effectively just 'blowing up' the object from the central portion of the lens/mirror, so are enlargeing any imperfections. After all the objective lens/mirror size remains the same, it is the eyepiece that then does the work, so in theory the image remains the same it is just that the EP enlarges it.

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I find the optimum balance between detail, brightness and resolution comes at about x1 per mm on most nights. For my scope that's x235.

Quite a few nights I use x294 and on those very rare steady nights x392.

So although it's true larger scopes take more magnification, atmospheric conditions won't allow you to get anywhere near on most nights.

I seem to be alone in the habitat of using high magnification because even when the atmosphere is unsteady there are usually moments of steadiness however brief.

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