Handbook for the SX remote control Spectrograph Issue 1, 17/8/20
The T2 thread is part of a removable barrel that is normally locked into a fine-focus sleeve by an M4 setscrew (accessible
when the box cover is removed). The fine focus sleeve is itself driven by the large ring gear, which is seen surrounding the
T2 adaptor. One rotation of this ring, moves the camera in or out by 0.75 mm, and permits the accurate focussing of the
spectrum onto the camera sensor.
As the spectrum is too long to be completely imaged with a typical CCD sensor, the focus assembly may be moved along
the spectrum, by rotating the drive screw gearbox that is seen at the right hand end of the cross slide. This function is pro-
vided in the Spectrograph control software.
As the grating is designed for a compact optical system, the available back focal distance for the imaging camera, is some-
what limited. It is typically about 20 mm maximum, and this is sufficient for most compact astronomical CCD cameras, but
not for a DSLR. We recommend using either the SX-694 or SX-814 mono cameras for high resolution imaging with good
sensitivity. Almost complete colour spectra may be recorded with an SX-M25C. The camera is screwed onto the T2 adaptor
and the correct spectral orientation achieved by loosening the focus lock screw and rotating the T2 adaptor. The approxi-
mately correct focal position can also be achieved by setting the T2 adaptor extension and fixing it with the lock screw. Fine
focusing is done via the spectrograph control software.
