The PixCel 237 can easily be converted for use as a color CCD imaging camera. Utilizing an internal color filter wheel, the camera can be used to obtain the red, green, and blue components necessary for RGB composite full color imagery. Unlike its larger cousins the ST-6/7/8, and their correspondingly bulky CFW-8 color filter wheel, the small CFW5C wheel fits neatly inside the camera housing. By simply replacing the generic clear/opaque wheel, there is no additional weight or bulk added to the camera. Users of the PixCel 237 (and PixCel 255/ST-5C) should be aware there are two color filter wheels for these cameras. SBIG recently began selling a new filter set, designed to give better color balance with the PixCel 237/255 cameras. By using filters with a broader blue passband and narrower red passband than the old filters, and with IR blocking coatings the RGB filters, this new wheel affords better color rendition. The old filter wheel required the use of a threaded IR rejection filter which had to be removed prior to imaging in black and white. The new set makes it is easier to switch from RGB to B&W images, where you may wish to capture the IR by simply selecting the clear filter which does not have an IR block coating. When purchasing a filter wheel, make sure to specify the new band pass filter set. Transmission data for the filter set can be viewed at http://www.sbig.com/sbwhtmls/filterchart.htm.
Installing the CFW5C is easy and straightforward. The links below detail the process.
INSTALLING THE CFW
CHANGING THE PIXCEL 237 DESICCANT PACK
Most all CCD cameras (the PixCel 237 included) contain some type of silica desiccant. This desiccant absorbs water vapor from inside the camera. Since CCD cameras utilize a thermoelectric (TE) cooler to lower the operating temperature of the chip, any water vapor inside the camera can condense as frost on the chip itself. The desiccant pack will eliminate this, but will age over time. The average life expectancy of a desiccant pack is about one year. After that, or whenever frosting is noticed, the pack should be replaced. Replacement packs are available from Celestron and SBIG for a nominal fee. The old pack can be rejuvenated by baking the desiccant sans packet in a conventional oven at 400 degrees Fahrenheit for four hours. This should be viewed as a short term solution to replacement.
