FILTER WHEEL

Andy Saulietis (e-mail: iss@pvtnetworks.net) designed and built a manual filter wheel to be used with a CB245 CCD camera and 25mm Edmund Scientific Filters. Al Kelly and I have been using this set up for our color imaging and have found Andy's Filter Wheel and the Edmund Scientific filters to work really well. So, here's some info for folks that might want to consider using the same system:

RGB Filter set: Part # D52,546 for three unmounted 25mm dia, 2mm thick, additive dichroic filters ($53.50+shipping)

CMY Filter Set: Part # D52,549 for three unmounted 25mm dia, 2mm thick, subtractive dichroic filters ($53.50+shipping)

IR Cutoff Filter: Part # D53,710 for one unmounted 25mm 1.1mm thick filter ($38.15+shipping)

Clear Filter: Part # D32,951 for one unmounted 25mm dia, 2mm thick filter, AR coated both sides, one wave flat ($13.00+shipping)

The filter wheel itself hold four filters (3 colored filters and a clear filter). Since all 4 filters are the same thickness, no refocusing is required when changing filters. Dichroic filters were used for both low cost and high transmissivity. The IR Blocker has, in my opinion, a much sharper and better high end cut off than the SBIG KG-5 (both filters were tested with a spectrophotometer here at the Johnson Space Center). My IR blocker is mounted in a plastic disk that fits into the cavity in the front of the camera face and remains in place for all images (color and clear) to insure good color balance.

The following pictures should help illustrate the configuration of the filter wheel and camera setup:

	LEFT: Exploded view of the Filter Wheel Assembly, including two interchangeable filter wheels (one used for an RGB filter set, the other for a CMY filter set, both have a 4th hole with a clear filter in it), IR blocker in a plastic disk/cell, 1.25" adaptor and t-thread adaptor, light shroud and filter wheel turning tool (a "pop-rivet" on a lanyard). The two long handled screws at the top and the small silver one clamp the camera into the filter wheel housing, the two brass knurled knobs hold the bottom of the assembly to the top, capturing the filter wheel itself and allow rapid changes between the RGB filter set and the CMY filter set.
RIGHT: Assembled Filter Wheel assembly with IR Blocker ready to be inserted into the face of the camera, and then the camera inserted into the Filter Wheel Assembly housing.
	LEFT: IR Blocker inserted into the face of the camera, Filter Wheel Assembly mounted (via the t-thread adaptor) onto the camera/eyepiece slide made by Roy "Dutch" Teagle, camera ready to be placed in the Filter Wheel housing and clamped in place with the screw knobs. The slide allows swapping between an eyepiece and camera.
RIGHT: Camera and IR blocker inserted and clamped into the Filter Wheel housing, light shroud and "pop-rivet" turning tool ready to be slid up and over camera/filter wheel. One of the water cooling line quick disconnects is shown in the lower left corner.
	LEFT: Filter Wheel mounted on an EP projection tube (bottom of filter wheel has female t-threads), IR blocking filter in its plastic disk/cell, and light shroud/turning tool lanyard. Filter wheel has small holes in edges to insert tool into for turning. Filters lock into place via ball spring detents. Filter position is identified by lettering on edges of filter wheel itself. EP Projection tube also can mount onto the filter slide in lieu of using the 1.25" adaptor shown on the end of the EP projection tube (VERY handy to use the slide with the much smaller FOV during EP projection imaging)