CELESTRON PIXCEL 237/SBIG ST-237 CCD CAMERA

CELESTRON FASTAR 8 AND FASTAR 11

Celestron International's foray in to the world of CCD cameras began with the introduction of the PixCel 255.  This camera was subsequently replaced by the PixCel 237.  In June 1999, Celestron discontinued sales of the PixCel 237, relying upon SBIG to market their identical ST-237 for use with the Fastar system.  The 237 is reasonably priced,  and represents one of the best investments in the rapidly changing arena of CCD cameras.  The camera utilizes a Texas Instruments TC-237 chip with an array measuring 640x480 pixels (4.7 by 3.6 mm).  The chip contains a total of 307,200 7.4 by 7.4 micron picture elements, making it about twice as big as the PixCel 225's TC-255 chip with four times as many pixels.  The PixCel 237 enjoys perhaps the highest quantum efficiency of any amateur CCD camera (nearly 50% in the green and blue, and peaking at 75% in the H-alpha).   The smaller pixels and correspondingly smaller full well capacity make for efficient use of a 12 bit A/D converter, instead of a 16 bit unit.  It should be noted that this converter offers no loss of quality for this chip.  The 237 has 100% antiblooming and up to 3x binning, and features built in electric TE (thermoelectric) cooling.  A color internal filter wheel is an option.  Most of the control electronics are housed in a separate CPU box, with parallel port connection to any PC.  Image download times are very quick.

The PixCel 237 works beautifully in combination with the new Celestron Fastar-compatible Schmidt Cassegrain telescopes. (It should be noted that the original Fastar telescope has been discontinued by Celestron.  Now all 8 and 11 inch Celestar/Nextar and Ultima series scopes, and the C-14, have the Fastar option built in.)  These scopes have the unique ability to be used in many photographic configurations.  They can be used at f/10 (or f/6.3 to f3.3 with optical reducers), at f/20 and higher with appropriate Barlow lenses, and at f/2 prime focus.  The latter is the most exciting.  By actually removing the secondary mirror from the corrector plate, and attaching a set of special optics, the telescope can be used for wide field imaging, by CCD standards.  Think of it as a CCD Schmidt camera.  In this configuration the field of view of the Fastar 8 is approximately 30 by 40 minutes of arc, or nearly two-thirds of a degree wide.  For such a small chip, this field of view is astounding.  With the CCD camera attached to the front of the telescope at prime focus (and owing to the fast f/2 ratio), images that would ordinarily take many minutes can be achieved in seconds.

Fastar and PixCel 237 Imaging Tips

Links to Other Fastar Web Sites


Celestron Fastar Imaging Group
 


CELESTIAL IMAGERY

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