Optec 6-position Filter Wheel for 50mm Square Filters with mounting tabs

Starting Price: $345.00
Price as Configured: $345.00
Brand: Optec / SKU: OP-17362
Wheel design allows for up to 6 filters of 50mm square size to be user installed. The 50mm square filters are not available from Optec but are commonly available from other astronomical filter suppliers. Wheel can easily be inserted into the filter wheel selector without removing anything from the instrument train. Tab and spacer kit #17585 is included. This configuration requires the Rear 3” Cover plate #17367 and the Telescope Adapter for 3” #17368.
Price as Configured: $345.00
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The new 58mm square filter standard from Optec offers a clear diagonal measure of 79mm or 3.1 inches. This size makes full use of the aperture available with the 3-inch line of Optec instruments. The large 35-37 mm square CCDs are covered without vignetting with these filters.

These filters have the same quality and transmission specifications as our popular 50mm round LRGB H-alpha and OIII filters. Scratch and dig is held to 60-40, wavefront distortion to less than 1/4 wave, and peak transmissions greater than 90% in the pass band. Filter thickness is 2mm.

Finally, the price of the Optec 58mm square filters is less then the premium 50mm square filters available from others. A complete set of LRGB and H-alpha filters to fill one of the 58mm square 5-position filter wheels for the IFW 3" cost only $1590.00. This set includes The LRGB set #17274 and the H-alpha filter #17275.

Shown above is a diagram based on the new PlaneWave CDK 12.5 inch telescope which has a f/8 cone and a wide well corrected field. Cameras with the KAF-09000 CCD have a diagonal image area that is 52mm accross. A 50mm square filter would have to be mounted within 5.4 inches of the CCD to avoid vignetting the corners. This would not allow the use of TCF-S3 to be used between the filter wheel and the camera since its back-focus distance alone is 5.5 inches to the mid point of travel. The use of 58mm square filters provide about 9.5 inches between the filter and CCD which allows the TCF-S 3-inch to be used. Having the filter far from the CCD avoids shadows from dust spots or filter defects from effecting the image. In addition, the ghost images and halos from multiple reflections between the filter and the CCD surface are also reduced.