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# light gathering

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How much more light will a 150mm scope gather over a 114mm......tried to search for an answer  but couldn't find one..?

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(150x150)/(114x114) - ignoring the difference in the secondary obstruction.

Edited by Demonperformer

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Its a simple calculation to perform.  Given the area of a circle is pi * radius squared, we can ignore pi as they cancel and just compare the square of the radius.  So the 150mm scope has a radius of 75mm and the 114mm is 57mm.  Divide the square of 75 by the square of 57 and the result is 1.73, which means 73% more light collected.

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You always lose a bit of light on the way, but
if you  compare 150 mm telescope to a well matured, dark adapted naked eye pupil (5 mm) you get

( 150 / 5 ) squared =
30 squared =
900 times as much light if you look through the telescope.

Have you looked at the Skywatcher Heritage-130p yet?

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But, an object will never be any brighter than naked eye, just enlarged to a bigger image scale at the same brightness (if the exit pupil matches your dilated iris).  You need to go to night vision technology to increase the brightness of truly faint objects over their naked eye brightness.

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Thanks guys.......Im 65 so my exit pupil may not be too good ( I can walk about without glasses after 2 cataract ops now though  for first time in 28 years :-) )

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