|
Meade Super Plossl
Eyepiece is the most cost effective Meade eyepiece. Meade Super Plossl
Eyepiece are good quality at reasonable price. I have an entire
collection of Meade Super Plossl Eyepieces.
Magnification or power of the Telescope with a certain eyepiece can be
calculated as the result of the focal length of the telescope divided by
the focal length of the eyepiece.
M = Telescope focal length / Eyepiece Focal Length
Meade Super Plossl 26mm eyepiece on an ETX-90EC (1200mm) telescope
gives you a 48X magnification. Meade Super Eyepiece 6.4mm
eyepiece on the same telescope gives you 195X magnification.
This does not mean you can have higher magnification by putting
in shorter focal length eyepieces without limitation. The
limitation is often the image gets darker and darker as the
image gets bigger and bigger. Since the same amount of light
collected by the telescope must spread over a larger image
area, the image gets darker. Every time the image size is
doubled, the light becomes 1/4 as bright. Very high power
magnification is only sensible on very bright stars or planets
like the moon.
There is a maximum magnification for any telescope beyond which the
image would be too deteriated to count. The practical rule
is 2 times the aperture in mm or 50 times the aperture in
inches. Therefore the ETX-125EC has a maximum useable magnification
of about 250X. the ETX-90EC about 180X. You have to have perfect
observing condition to get to that kind of manigication.
Bigger image also mean the image will not be as sharp and depends on
the quality of the telescope optics,
|
