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Difraction Rings

Posted: Mon Apr 05, 2021 5:19 am
by Jones
Why does my 6"f6 GSO newt show a prominent 1st difraction ring,
while the Edmund 6"f8 reveals just a faint one?

Neither could see the 'f' star in the Trapezium.

Re: Difraction Rings

Posted: Mon Apr 05, 2021 4:50 pm
by Bigzmey
I believe it has to do with F-ratio and size of the central obstruction. The larger central obstruction the more light is distributed from the airy disk to the first diffraction ring. Faster newts tend to have lager secondary mirrors compared to slower.