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The KAF-8300 CCD is approximately 18 x 14mm and has a diagonal measurement of about 22 millimeters. This is about 1.6X the image area of an ST-10 and nearly the same area as the STL-4020C. With its relatively small pixels and large image area it is ideal for wide field imaging with short fast telescopes and camera lenses and at the same time is flexible enough to be used on long focal length Schmidt-Cassegrains. The STF-8300C color camera can be used with a filter wheel in any of several binning and partial frame modes for narrowband imaging. Binned 2x2 the pixels are 10.8 microns square and binned 3x3 they are 16.2 microns square. At 2x2 the array is still 2 megapixels and at 3x3 just under one megapixel. This feature makes it possible to match the pixel size to your seeing and scope, from a small refractor to a large SCT. With the STF-8300M monochrome camera binning will not only help optimize the sensitivity of the CCD with the user's optics and seeing conditions, but also speeds up the download rate. SBIG software drivers allow the user to combine any of several binning modes and partial frame in various ways to suit the user's optics, seeing conditions and objects of interest. For example, when imaging planets the sensor can be used in high resolution (5.4 micron pixels) mode while downloading only a quarter frame to speed up the data collection process. On nights of less than good seeing, or when used at longer focal length scopes such as Schmidt-Cassegrains, the sensor can be binned 2x2 or 3x3 in full frame mode to match the conditions while maintaining the full field of view of the CCD. These frame and binning modes, coupled with the large sensor area and 8.3 megapixel array make the STF-8300 cameras extremely versatile and adaptable to a very wide variety of telescopes and conditions. For these reasons, plus the camera's small size and breakthrough price point, we feel the STF-8300 is an ideal camera for those stepping up to a cooled low noise astronomical CCD camera from a DSLR and a superb backup camera for even advanced users.
A mechanical shutter is included to facilitate dark frames. This is a necessity for anyone operating remotely, even if remotely means a few feet away from the telescope. Adding a shutter to a camera design increases the cost and size of the camera body but we feel these trade-offs are worth the added convenience and functionality. Since the early days of the original ST-7 camera, SBIG has been providing even-illumination shutters in our cameras, something not found in the majority of other cameras made for astrophotography."Even-illumination" means that the shutter mechanism is designed to open and close in such a manner that it does not change the proportion of light falling on the sensor due to the shape or motion of the shutter itself. This is what one finds for instance with an iris type of shutter that opens-up starting at the center and closes over the center last. In the STF-8300 we use a simple and very robust shutter wheel with a fan-shaped aperture of the same design that we have employed in the ST series cameras for the past 15 years. The STF-8300 shutter sweeps over the CCD without leaving any area of the sensor exposed for a different period of time than any other area. Another benefit of the rotating disk type of shutter is that it has only one moving part - the motor. These motors are extremely reliable and can operate for millions of exposures without failure. In 15 years with thousands of cameras in the field taking millions of exposures, this shutter design has proven itself better than we can describe. Our design is proven and reliable.
In our tests of production samples, the camera reached a maximum of -40 degrees C below ambient in a warm room in less than 3 minutes after the cooling was turned on. It was allowed to stabilize and after a few more minutes the regulation was enabled A few degrees were then given up for regulation with the camera running at only 80% TE cooling power to maintain -36 degrees C below ambient. Because of this CCDs extraordinarily low dark current, great temperature deltas are not required to achieve a dark current low enough that it becomes relatively insignificant compared to the read noise and sky background (See dark current data below). For example, in a test, one 15 minute dark frame taken at -10C was subtracted from another 15 minute dark frame taken at the same temperature. The total noise in the remaining image was ~15 electrons which included both dark current noise and read noise.This is exceptionally low.
According to Kodak, the dark current of the KAF-8300 is less than 200e- at 60 degrees C with a dark current doubling temperature of 5.8 degrees. This means that for approximately each 5.8 degrees C that one warms the CCD, the dark current is doubled, and for each 5.8 degrees C one cools the CCD the dark current is halved. Extrapolating this to -10C we can calculate the maximum dark current we can expect to find at that temperature. In fact, Kodak's specifications are usually very conservative when it comes to dark current, and this value can vary from chip to chip by 50% or more and still remain within the allowed specification. When we measured the 8300 CCDs we found many to be less than half of Kodak's allowed specification. This is also typical of what we have seen in other Kodak CCDs. In our tests we measured the dark current in some samples to be as low as 0.01 electrons at -10C. Again, these are extremely low dark current values for a full frame CCD. The Dark Current chart on this page has been updated using the average of the first production run of cameras. Even at zero degrees C the typical dark current is well below 0.2 electrons! At -10C the average of our current production units is around 0.04 electrons making it the lowest dark current of any camera currently made by SBIG.
In the past, one of the drawbacks in using sensors with small pixels and antiblooming structure has been the trade-off of some quantum efficiency. However, Kodak's microlens technology has largely made this trade-off a thing of the past. The KAF-8300 uses microlenses to focus more light on each pixel that would otherwise be lost due to the opaque antiblooming gate structure of the sensor. As a result, the KAF-8300 antiblooming protection can handle up to 1000X the full well saturation and at the same time this CCD has a quantum efficiency comparable to that of a full frame sensor without ABG. Moreover, the QE curve for this full frame sensor has a peak in the middle of the visual spectrum and good sensitivity well into the red and near IR. The QE at the important wavelength of H-alpha is nearly 50%.
Linearity is measure of how flat the CCD response is to light with increasing exposure times. For instance, an ideal CCD will record exactly twice the signal in a 20 second exposure as it does in a 10 second exposure from a constant light source. This is particularly important in photometric studies where the CCD is used as a tool for measuring light at various wavelengths to determine the temperature of stars. The sample we measured is about 10X better than Kodak's allowed specification, with a response that is within about 1% of linear (up to approximately 50,000 counts (binned 2x2).
The STF-8300 will download a high resolution, full frame image in less than 1 second, and focus with screen updates faster than once per second in planet mode (a high resolution 20 x 20 pixel box located anywhere on the CCD by the user) when connected to a high speed USB 2.0 port. Full frame low resolution, high sensitivity finding and focusing may be used to increase the update rate. The camera is also compatible with USB 1.1 ports albeit at a slower download rates.
A feature first introduced in the STF Series, and found on no other astronomical CCD camera, is user selectable internal image processing. For those times when you want quick results, and don't want to spend a lot of time post-processing you images, the internal image processing feature can make your raw, unprocessed images look great. Simply select the level of processing you desire (0-8) and the images are automatically cleaned of hot pixels.
The 9-pin I2C port allows the use of our filter wheels with the same interface. The power and commands for the filter wheel all come from the camera through this port, so there are no other cables or power supplies needed to operate the filter wheel. Also, the same software that controls the camera also controls the filter wheel. SBIG offers two custom filter wheels for the STF-8300M camera, a 5-Position wheel and an 8-Position wheel. Both are thin enough to accept a Nikon lens adapter for shooting filtered images through any Nikon 35mm lens. In both cases, automatic exposure sequences may be set in advance for hands off acquisition, or the user may control the filter wheel for each exposure if desired.
The guider port on the STF-8300 is the same as on the other ST cameras, using a modular telephone type 6-pin jack to connect the STF-8300 to the user's mount when using the camera as an autoguider. The internal relays used in the STF-8300 design are opto-isolated, so that no external relay box is required with any mount if the camera is being used as an autoguider or if it is being used to control the telescope in Track & Accumulate mode. Of course, a relay box can still be used, although not required, for convenience if the user already has one wired to a mount for another camera.
Although small and light, the camera is built to last. The front plate, main body and rear plate are each machined from solid aluminum block for maximum strength and then hard anodized over a special bead blasted finished for durability. Connector labels are laser etched and will never wear off.
The STF-8300 comes with its own universal AC power supply. This supply will operate from 100-240VAC and provides 12VDC at 3.75A to the camera. The STF-8300 also has a built-in voltage regulator and can therefore be powered directly from any unregulated 12V (10 - 14 volts) source such as a battery for operation in the field. The universal AC power supply is relatively small (1.2x2.3x5.2 inches, 30 x 58 x 132mm) and light weight (9 ounces, 254 grams). SBIG also sells a 12VDC battery cable with alligator clips and a cigarette lighter adapter plug.
- Rugged camera body with rack handles and 2" nosepiece
- KAF-8300C imaging CCD
- High speed USB 2.0 interface
- I2C bi-directional accessory port for integrated filter wheel control
- Standard guider output port (ST-4 pinout compatible with internal opto-isolated relays)
- Internal mechanical shutter
- Large Cooling Fan
- User rechargeable desiccant plug
- Tripod mount 1/4-20 threaded side plate
- 15 foot USB cable (third party USB extenders available)
- Telescope interface cable (for guiding)
- Universal 100-240VAC Power supply
- SBIG's CCDOPS version 5 camera control software
- Printed Operating Manual
- Hard carrying case with pre-cut foam for your camera and small accessories
- Demo CD-ROM with sample images and software
|Type:||Camera CCD raffreddata|
|Resolution||3326 x 2504|
|Sensor dimensions (mm)||17.96 x 13.52|
|Sensor diagonal (mm)||22.6|
|Pixels dimensions (µm)||5.4|
|A/D converter||16 bit|
|Cooling||-40°C rispetto a T ambientale|
|Readout Noise (e-)||~9.3e-|
|ST4 integrated autoguide port||Yes|
|Telescope interface||Female T thread (42x0,75)|
|Connection to PC||USB 2.0|
|Power||External 12V 3A|