Starlight Xpress SX User Manual

Handbook for the SX Universal Filter Wheel - Issue 1, May 2009

Handbook for the Starlight Xpress Universal Filter Wheel

Thank you for your purchase of a Starlight Xpress Universal Filter Wheel. We hope
that you will enjoy using this advanced SX unit, which offers many unique features.
This handbook will help you to put it into operation and to understand its capabilities.
Please read it carefully.

Description:

The SX Universal Filter Wheel has several important advantages over older and less
sophisticated designs:

1) The wheel uses an internal sub-miniature DC motor drive to turn the filter

plate. This consumes far less power than the more typical stepper motor and
allows wheel operation directly from the USB input, thus eliminating the
cumbersome power supply and extra power cable. The DC drive also produces
a quiet and vibration-free filter translation and eliminates a significant amount
of bulk and weight.

2) The filter locations are encoded by 3 Hall-effect magnetic sensors, which

permit up to 7 unique filter positions to be defined. The control software can
specify a particular filter without prior knowledge of the location of ‘position
1’ – so the filters can never get out of sequence. The lack of any infrared

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Handbook for the SX Universal Filter Wheel - Issue 1, May 2009

optical sensors also prevents stray infrared light from entering the CCD
camera and causing strange image artefacts.

3) Although USB operation is the normal mode, the extra RJ12 socket also

permits serial port control or ‘handbox’ manual control. The Universal Filter
Wheel truly is ‘Universal’!

4) The input and output adaptors are both removable and also may be oriented at

any rotational angle to set the wheel and camera into optimum positions. The
standard ‘T’ thread adaptors may be replaced with other versions for ‘SCT’
thread etc. simply by unscrewing three fixing bolts.

5) Two interchangeable filter plates are available – one with seven x 32.5mm

filter positions and the other with five x 48mm filter locations. These are
easily swapped by removing 6 ‘thumbscrew’ fixings and simply dropping the
plate into place. There are no gears or belt drives to engage and the plate drops
directly into contact with the motor drive drum. Easily done, even by
flashlight!

6) The ultra-slim design of the SXUFW minimises the loss of optical back focal

distance to only 29mm overall (including the T thread adaptors).

Here is a simplified cross-sectional view of the filter wheel

Loading the filters:

Open the wheel by unscrewing the 5 small thumbscrews from around the periphery of
the wheel chamber and the single large thumbscrew from the central pillar. Carefully
lift off the side wall and put it in a safe place. You will now see the filter plate and
you can lift it off the centre bearing and place it down with the magnet screws facing
upwards. Your filters may now be screwed into the plate from the magnet screw side,
placing them in the desired numerical order according to the engraving on the plate.
Assemble the wheel by reversing the sequence of operations above.

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