APERTURE...THERE IS NO SUBSTITUTE.

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Telescope Aperture Comparison Chart

Take a look at how much more light a telescope gathers with just a small increase in diameter:

Primary Mirror Size        Square Inches of Aperture

                       4"      12

                       6        28

                       8        50

                     10        78

                     12      113

                     13      133

                     14      154

                     15      177

                     16      200

                     17      227

                     18      254

                     20      314

                     22      380

                     24      452

                     25      490

                     28      615

                     30      706

                     32      803

                     36    1017

       Meter(40")    1256

  Telescope Aperture Formula:

R²*Pi

R = The Radius of the mirror.

Pi = 3.14

So, for a 26" diameter mirror we take half of the Diameter to get the Radius :

26 / 2 = 13

and square it (multiply it times itself)

13 * 13 = 169

and finally multiply it by Pi (3.14)

169 * 3.14 = 530.66

so we would say a 26" mirror has 531 square inches of aperture.

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