maximum magnification

opticsplanet.com · Posted: Thu May 19, 2005 1:31 pm Post subject:

Hi

This is a common question to which there is no quick answer, but the maximum visual power or magnification listed for any telescope is pretty meaningless. For one thing, most manufacturers vastly exaggerate this and, for another, the only magnification that counts is useable magnification. By useable, we mean magnification that still has enough clarity to show the detail you want.

The maximum useable magnification will vary with seeing conditions, the type of object being observed and the size of your scope. Bright objects such as the moon and planets can take much higher magnification than dim nebulae and galaxies. Since a basic law of optics states that image brightness decreases as magnification increases, it is possible in a small scope to crank the magnification so high as to make a faint object invisible!

For a scope the size of the 125, you will find that 150-200x on nights of good seeing will be your most used range - it's my favorite on my 5" Mak and I often use less for large clusters and nebulae or a bit more for double stars. I could, of course crank up the magnification much higher, but image quality would be so poor as to be useless and definitely not enjoyable.

Going to a larger scope will allow you to bump up the power, of course, but at the expense of portability and convenience. The ETX-125 is a wonderful scope that will give nearly as good an image as the big boys, but with much less hassle.

Enjoy the view.
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