To calculate an eyepiece's magnification, divide it's
mm number into the focal length of your scope. For example, an
8" SCT with a focal length of 2000mm will yield the following
magnifications:
52mm = 38x
40mm = 50x
32mm = 62.5x
26mm = 76.9x
20mm = 100x
15mm = 133x
12.4mm = 161x
9.7mm = 206.2x
6.4mm = 312.5x |
We recommend the use of a Barlow lens, which
effectively doubles an eyepiece's power by cutting the mm number in
half, while also increasing eye relief, a plus for any observer.
Choose your sets carefully, though, because you may get little
benefit, for example if, you bought a 40mm, 20mm, and 10mm. With a
Barlow, the only new power you'd get would be 5mm. But choosing a
40mm, 26mm, and 15mm, in this case, would give you a wider range
with a Barlow. You would effectively end up with a 40mm, 26mm, 20mm,
15mm, 13mm, and 7.5mm, giving you smooth increases in power without
repetition and waste!
That's 50x, 76.9x, 100x, 133x, 153x, and 266x-- a nice assortment!
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