Its objective is a single lens of 53 cm diameter and 8 meter focal length, the effective focal length is 12 meter by means of an auxiliary optical unit, so the observed diameter of the solar disc is about 12 cm.
(the observed diameter of the solar disc; is; about 12 cm) (the effective focal length; is; 12 meter by means of an auxiliary optical unit) Context(the effective focal length is,List([75, 104))):(Its objective; is; a single lens of 53 cm diameter and 8 meter focal length)
the effective focal length is,List([75, 104))
the observed diameter of the solar disc the effective focal length Its objective
is is is
about 12 cm
12 meter by means of an auxiliary optical unit
a single lens of 53 cm diameter and 8 meter focal length