LIGHT-RECORDING POWER OF A SYSTEM

[Coco]

Can any boffin's here please point to a calculator that I can use to work out the text below, i want to work out how much much more light recording power my scope has at 110mm f/4.72 vs 110mm f/5.9... am rubbish at this type of math.

LIGHT-RECORDING POWER OF A SYSTEM: Power = r^2/f^2

(the light-recording power is directly proportional to the square of the radius of the objective and inversely proportional to the square of the f-number)

• where Power is the light-recording power of the system
  r is the radius of the objective
  f is the f-number (f/) of the system
  

Example: a 200-mm f/8 system compared with a 100-mm f/5 system

(100^2)/8^2 compared with (50^2)/5^2

156.25 compared with 100, or 1.56 times more light-recording power

[Freddie]

Hi, I make it 543.12 against 347.6. so the f4.72 is just over ona and a half times greater or 1.563 to be accurate.