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Old 28-06-2015, 09:47 AM
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Peter Ward
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Join Date: Dec 2007
Location: The Shire
Posts: 6,809
Reminds me of the Physicist who needs some dry-cleaning done...& spots a sign in a local shop (oddly, run by a Mathematician). The sign reads
"Dry cleaning done here".

So he walks into the store and plonks some laundry on the counter, and asks
the shop-keep to clean it.

"No!, sorry, we don't do dry-cleaning!" says the shop-keep to the now puzzled Physicist.

"We only make signs!"

My point being, while the F-ratio is an interesting measure of a systems "sensitivity"... fact of the matter is: you still need flux. The ability to capture flux is by-and-large determined by aperture.

The dragonfly 'scope is described by adding extra lenses, as making the system "faster"... but in reality this is being done by increasing the effective aperture (rather than reducing the focal length).....hence I pondering whether this is simply a bit of mathematical sleight of hand.
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