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Focal Ratio
F Ratio or Speed
want could this mean?
By Greg Walton MPAS/ASV
In astrophotography we are
usually pushing the camera and lens to the limit, running
high ISO settings for long periods of time. We very rarely
stop a lens down; in the diagram below all Lenses are the
same Diameter with different F ratios.
The bigger the patch of sky the more light it contains and
the brighter the picture will be.
I hear you say what is an F ratio? It is how
many times the lens diameter, can fit into the focal length
of a lens. See scale on left. The boxes at the bottom of the
page are a comparison of the amount of sky that can be seen
with a curtain lens F ratio.
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Public Viewing
Nights |
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Just to let
everyone know, public viewing nights are held
every first Friday of the month. Clear or cloudy
nights the public viewing night goes ahead.
Members man a number of telescopes of various
sizes and types, and for those nights where the
sky is cloudy, extended astronomical presentations
are presented in the MPAS Viewing Centre.
So please come
along and enjoy our nights sky.
How to
get Here
(Click Here)
Where are
visitors seeking from..
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