More Information  · Recommended Accessories  · Images of Some Features

Also, the ST-8XME is well suited to TDI (Time Delay Integration) imaging. TDI lets you image large areas of the sky without guiding – so any telescope will do. In TDI, you point the camera at an area of the sky and turn off the telescope drive to let the stars drift across the field of view. The imaging detector is clocked in sync with the rate of stellar drift to keep the accumulating charge underneath the star’s image until the star reaches the edge of the CCD, and the readout register. The resulting image has an exposure time equal to the amount of time it takes the stars to drift across the CCD. Depending on the focal length of the scope, this can be many minutes. Because the scope itself is not moving, there is no periodic error and no guiding error during the exposure! Furthermore, the image you are recording scrolls as the sky moves past, so the image file can be 1020 pixels tall by 1000 pixels in width, or 2000 pixels wide, or 3000, etc.

The ST-8XME uses two CCD detectors. One is a 1530 x 1020 pixel Class 2 detector without anti-blooming for collecting the image. The other is a 657 x 495 pixel detector for guiding. The detectors are mounted in close proximity to each other within a single camera body. They are focused at the same image plane. This patented guiding method allows you to focus both taking and guiding detectors simultaneously. Some competitive cameras require a separate guiding detector in a separate housing that mounts in an off-axis guider body. Such a two-housing system requires more setup time to focus each detector independently than the one-time focus of the ST-8XME. Still other cameras have one detector, but use a portion of that detector to guide while the balance of the detector collects the image. By using a separate CCD for guiding, the ST-8XME allows 100% of the primary CCD to be used to collect the image, an improvement over this latter type of single chip design.

The imaging CCD is the new enhanced KAF-1603ME chip with microlens technology from Kodak for much higher quantum efficiency (QE) across the entire UV to IR spectrum than previous detectors. The high QE makes the ST-8XME perfect for imaging deep space objects such as dim galaxies and emission nebula. Peak QE occurs very near the H-alpha emission line at 656 nm, making this camera extraordinarily sensitive at this photographically important wavelength. It could be said that the ST-8XME was “made” for capturing H-alpha. Previously, this level of QE was achievable only through the process of thinning the detector wafer and illuminating the image sensor from the backside. However, thinned and back-illuminated CCDs are very expensive to make and buy. With the KAF-1603ME front illuminated detector, similar performance to a back-illuminated CCD is achieved with lower dark current and superior cosmetic specifications (the number of pixel defects) – and at a much lower cost. Peak quantum efficiency is almost 85%, making this camera the most sensitive in its class. In order to provide the largest full well capacity for linear response scientific measurements and the widest dynamic range for imaging, the ST-8XME does not have built-in antiblooming (ABG).

Kodak classifies their imaging detectors according to the number and type of pixel “defects” found on the chip. “CCD Point, Cluster, and Column Defects” are defined in the “Astronomical Terms” section above left. The Class 2 chip of the ST-8XME has no more than 10 point defects in its entire 1.5 megapixel imaging area (no more than 5 in the central 600 x 800 pixel area); no more than 4 cluster defects (a maximum of 2 in the central 600 x 800 pixel area); and no column defects. The few point and cluster defects of the ST-8XME are easily removed from an image during processing.

No special orientation of the SBIG camera is needed for proper guiding with the built-in guiding detector. In tests, even when randomly pointing the telescope toward objects in relatively star-poor areas of the sky away from the Milky Way, stars on the guiding detector of the ST-8XME were bright enough to be used for guiding 95% of the time. In those few cases where a bright-enough guide star might not be immediately apparent, TheSky software from Software Bisque (supplied with the ST-8XME) can print finder charts showing the correct orientation of the guiding detector’s field of view relative to the imaging CCD's field of view for proper guide star acquisition.

Carefully guided exposures up to one hour are possible with the ST-8XME, enabling a standard 8” Schmidt-Cassegrain to capture images showing 19th magnitude stars from typical background observing sites. Pixel binning modes (1x1, 2x2, 3x3) allow the user to match the pixel size to various focal lengths ranging from long focal length refractors and SCT's to short focal length camera lenses. The imaging camera includes a mechanical shutter, 16-bit analog to digital (A/D) converter, regulated temperature control, and has all of the electronics integrated into the CCD head. Communication to your PC is through new high speed electronics and a high speed USB 1.1 interface. Data transfer rates are up to 420,000 pixels per second, allowing a full frame download in 3.7 seconds (images download at approximately 2 per second in the focusing mode).

The standard cooling configuration is a single stage thermoelectric cooler with an active fan and a newly designed heat exchanger. It includes an inlet and outlet for water circulation should the user desire to maximize the cooling performance in warm climates. Typical cooling without water assist is -35° C from ambient (-30° C minimum). With water assist, the cooling increases to a typical -45° C. Even without water cooling, the new single-stage cooling design offers similar performance to previous two-stage cooling with much less current draw than a two-stage cooler. It is therefore less demanding on battery capacity when operating in the field. A circulating water pump and tubing are available as optional accessories.

There’s a new I²C accessory port that adds bi-directional communication capability for the coming development of a new family of "smart" accessories. A standard accessory port is also provided to maintain compatibility with the customer's existing telescope interface cables and backwards compatibility with SBIG’s existing accessories – such as the CFW8 color filter wheel, AO-7 adaptive optics system, and relay adapter box for telescopes that do not have a dedicated CCD guider input.

There is also a remote guide head port for using an optional external guider instead of the built-in guiding chip. This is sometimes helpful during color imaging through a color filter wheel. In some areas of the sky that have few reasonably bright stars to use for guiding, the color filters will dim the only available guide stars to the point where guiding with the camera’s internal guiding chip may become erratic as seeing conditions fluctuate. The use of an optional separate external guiding head will eliminate any such issues.

The camera body has rack handles that make for easier and safer handling of the camera, particularly in cold weather when wearing gloves; a high-speed USB 1.1 interface port; a user-rechargeable desiccant plug (there’s no need to return the camera to the factory for frosting problems); an internal shutter for automatic dark frames; a 2” nosepiece (a 1.25” nosepiece is optional); a T-thread ring for attaching to T-mount photo accessories; a 1/4”-20 thread side plate for tripod mounting; a 15-foot USB cable (third party USB extenders with a CAT5 cable are available for cable runs up to 300 feet); an adapter plug for the telescope interface cable; a telescope interface cable for autoguiding; a universal 90-240VAC power supply with a remote on/off switch; and a custom designed hard carrying case with pre-cut foam. You also get full working versions of SBIG's CCDOPS version 5 camera control software, Software Bisque's CCDSoft Version 5 image processing/camera control software, and Software Bisque's TheSky version 5, level II, with telescope control for Windows. All software and operating manuals are on CD-ROM.

While the software supplied with this camera is designed for use with a Windows-based PC, SBIG can also supply software to let Apple Macintosh owners control the camera. The software is available free from SBIG upon request to any new SBIG camera purchaser with proof of purchase. Simply send SBIG a copy of your invoice with the camera serial number and request the EquinoX Planetarium Software with SBIG Camera Control. The EquinoX software requires a Apple Macintosh computer (G3, G4 or G5), OS X 10.2 or later, 30MB of free RAM, and 92MB of hard disk space. The software can control all SBIG ST-series cameras and Ethernet cameras. OS X drivers for the cameras are also required and can be downloaded from SBIG at no charge.

Detector specifications are as follows:

Imaging Detector: Kodak KAF-1603ME, Class 2.
Pixel Array: 1530 x 1020 pixels.
Pixel Size: 9 x 9 microns.
Total Pixels: 1,560,600.
Full Well Capacity without ABG: ~100,000e-.
Dark Current: 1e-/pixel/second at 0 degrees C.

Guiding Detector: Texas Instruments TC-237.
Pixel Array: 657 x 495 pixels.
Pixel Size: ~ 7.4 x 7.4 microns.
Total Pixels: 325,215.

Readout specifications are as follows:

Shutter: electromechanical.
Exposure: 0.11 to 3600 seconds, 10ms resolution.
Correlated Double Sampling: yes.
A/D conversion: 16 bits.
A/D gain: >2.3e-/ADU.
Read noise: 15e- RMS.
Binning modes: 1x1, 2x2, 3x3.
Pixel digitization rate: up to 420,000 pixels per second.
Full frame acquisition: 3.7 seconds.

Optical specifications with 8” f/10 (2000mm focal length) scope are as follows:

Field of view: 24 x 16 arc minutes.
Pixel size: 0.9 x 0.9 arc seconds.
Limiting magnitude: magnitude 14 in one second.
Limiting magnitude for 3 arc second FWHM stars: magnitude 18 in one minute.

System specifications are as follows:

Standard cooling: single stage thermoelectric, active fan, water assist ready, -35° C from ambient typical (-45° C from ambient typical with water assist).
Temperature regulation: +/-0.1 degree C.
Power requirements: 5 VDC at 1.5 amps, +/-12 VDC at 0.5 amp desktop power supply included.
Computer interface: USB.
Computer compatibility: Windows 95/98/NT/2000/Me/XP.
Guiding: patented dual CCD self-guiding.

Physical specifications are as follows:

Optical head: measures 5 inches diameter x 3 inches deep (12.5 cm diameter x 7.5 cm deep), weighs 2.2 pounds/1 Kg.
CPU: no separate CPU required, all electronics integrated into optical head.
Supplied mounting methods: T-thread, 2” nosepiece.
Back focus needed: 0.92”/2.3 cm.