The camera software will keep the camera at that temperature, which results in much higher quality dark frames and, for that reason, less noisy final images. Like the ST402, most of SBIG's more expensive cameras use monochrome chips. Black and white chips are more sensitive than color chips but require three separate exposures through three filters (red, green, and blue) to produce color images.
In the opinion of some amateurs, the real meat of the SBIG line lies in its more advanced cameras. One favorite is the ST-2000 (Plate 75). The nicest things the 2000 brings to the table are a large 11.8mm x 8.9mm (1600x1200 pixels) CCD and, for the most expensive version, a separate guide chip. Telescopes must be guided— have their aim fine-tuned—during imaging if they are to produce round stars. The ST-2000 can be purchased with an additional, smaller CCD chip mounted alongside the imaging chip that allows the camera to guide and image at the same time (most cameras can do one or the other but not both). That makes it amazingly easy to get well-guided pictures with the ST-2000, even with less robust and less expensive mounts. For users wanting color pictures but not wanting to mess around with tricolor imaging, SBIG offers a one-shot color version of the ST-2000 that is gaining quite a few fans, including amateurs who previously disdained one-shot color.
The other long-time CCD player in the mid-range ranks is Starlight Xpress in the U.K. Although Starlight has never been as popular in the U.S. as SBIG (the situation is reversed in the U.K.), the company has plenty of fans on this side of the water, and, like SBIG, sells cameras all the way from the beginning to the near-professional level.
The junior member of the Starlight family, and the one that best carries on the tradition of the popular MX5 of yore is the SXVF-M7 ($1,600), with a monochrome 6.3mm x 4.76mm 752x580 chip. This camera features a regulated cooler, and, when this is coupled with its very low thermal noise characteristics, some users may be able to get by without taking a single dark frame. We described Starlight Xpress as being "innovative," and this little camera is one of the offerings that really shows that spirit of innovation, in this case with its "STAR 2000" interface.
The only CCD cameras on the market that feature separate guide chips are the SBIGs, since that's a proprietary and patented invention. In some ways, though,
Starlight's STAR 2000 system is even better; it allows guiding and imaging with the same chip at the same time. The optional STAR 2000 cable and interface box connect between the laptop and the mount's autoguide port and keep the scope positioned on the chosen guide star. How can it guide and image at the same time? The chip used in the M7 can alternate guide "fields" with imaging fields. Essentially, half a frame is imaging and half is guiding at any given time, with everything being reassembled by the computer when the exposure is over. The only drawback is that this unavoidably reduces the sensitivity of the chip, and the M7's chip is already less sensitive than that of the comparable SBIG ST-402.
Earlier it was said that Starlight cameras are not as popular as SBIG in the U.S. That's true, but Starlight's SXVF-H9 ($3,000) seems to be threatening to even the score. More and more of these are appearing at star parties, anyway. The H9 is a monochrome camera with a good-sized 9 x 6.7mm 1392x1040 pixel chip. Like the M7, it's got excellent noise characteristics, a regulated cooling system, and is capable of producing beautiful pictures. Since it is not compatible with the STAR 2000 system, Starlight offers a separate guide camera head for use with an off-axis guider or separate guide scope. Starlight Xpress has long been a leader in one-shot color cameras and makes color versions of the M7 and the H9, the M7C and H9C, respectively.
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