A folded Newtonian reduces the tube length of a telescope and as a result also the dimension of the observatory.
In addition the height of the eyepiece is at a much lower level than the standard Newtonian.
An extra provision is made by ASTROFOX by making the upper cage turnable to create optimal accessibility at
the eyepiece. By using a computer program the obstruction ratio caused by the round flat and the elliptical secondary could be held as small as possible, and depending on the focus length are in most cases the same as the Schmidt/Cassegrain type telescopes, about 30%.
An electric focusing unit with stepper motor control, with manualpanel designed with digital output and RS-232 port for computer editing, is installed on the round flat instead of on the eyepiece holder to guarantee backlash free motion and a superb accuracy. It also avoids Long tubes on the eyepiece holder that might cause instability.
To correct for coma a special designed corrector can be used, or a tele extender when a longer focal length is desirable.
This telescope is especially advisable from a diameter of 20" and up, and therefore is much cheaper compared to the short tube systems like the Schmidt/Cassegrain types. Recently a 20 inch folded Newtonian was installed for a university in Thailand, and a 36 inch folded Newtonian is in progress and will be installed in May at URSA observatory in Finland.
The equatorial mounting
Any type of mounting can be used, but because the tubelength is smaller, a fork mount is now advisable.
The mounting for the 36 inch has a fork mount, and the polar axes are fixed.
The fork has internal bearings and is driven by friction drive by an 800mm diameter wheel, as well as the declination axes.
A microstep control system from AWR made in England will give all the necessary movements and control and can be linked to the most Astronomical computer applications, like "The Sky".
