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This webpage is to provide information on the optical elements of the Cassegrain Acquisition and Guidance Box WHT.
CASS A&G box
NEW (Dec 2012): Display this Vignetting Technical Note ('Save link as...' to save the PDF) on previously unknown contribution from the baffle at the secondary mirror.
Vignetting at the
various foci. The curves show the percentage transmission as a function of
field radius. For accurate photometry, this should be used only with caution
(see text). These curves refer to the area outside the constant central
obstruction of 8.4 per cent (Table II) and supporting vanes obstructing
0.6 per cent.