The QSI 660wsg-8 model camera employs a 6.1mp Sony CCD image sensor. This new generation of Sony sensor offers remarkable sensitivity with peak QE of over 75%. The high senstivity, wide dynamic range, dual read rates, low noise performance and internal 8-position color filter wheels make the QSI 660wsg-8 ideally suited to a broad range of demanding scientific, medical, astronomical, and industrial imaging applications.The 2758×2208 sensor in the QSI 660wsg-8, provides extremely high resolution with its 4.54µm pixel.
The compact design and internal color filter wheel of the QSI 660wsg-8 allows unvignetted, filtered images even with very fast optical systems.
The QSI 660wsg-8 camera employs a Sony ICX694 6.1 megapixel interline transfer CCD image sensor with microlens technology. The Sony ExView sensor has exceptional sensitivity across the visual band with peak quantum efficiency of 77% along with remarkably low dark current. The sensor has antiblooming protection and a fast electronic shutter. Micro lenses cover the surface of the CCD to focus the light into each 4.54µm pixel to increase optical response.
Key in the compact design of the 600 Series cameras is a very efficient custom 2-stage thermoelectric cooler (TEC) subsystem. Intelligent, programmable cooling fans are integrated into the rear of the camera body to remove the heat generated by the cooler. Typically, forced air cooling lowers the regulated CCD temperature by up to 45°C below ambient utilizing 85% power. Tight +/- 0.1°C temperature regulation is maintained at temperature settings of 10°C below ambient and lower. A slim liquid heat exchanger (shown at right) can be attached to the rear of the camera body to increase the cooling further, up to 55°C below the temperature of the circulating fluid.
The cooled CCD image sensor is positioned in a hermetically sealed environmental chamber covered with an anti-reflection coated precision optical window. The chamber is purged with an ultra-dry noble gas to increase heat conduction and eliminate the possibility of frost forming inside the chamber. To extend the useful period before re-purging is required, a user-rechargeable microsieve desiccant is employed to scavenge water molecules that enter the chamber. It is located behind a sub-micron, gas-permeable membrane to prevent particulate contamination of the CCD chamber.
Cooling and Dark Current
Effective cooling of the CCD image sensor is essential for long-exposure imaging, especially in astronomy. Thermally generated electrons accumulate in the pixels over time and compete with the photo-electrons that make up the image. This accumulation of thermal electrons is known as ‘dark current’. It lowers the dynamic range of the sensor and reduces the signal-to-noise ratio. Eventually, the thermally generated electrons will swamp the image.
Fortunately, dark current can be reduced dramatically by cooling the CCD. Sony ExView CCD sensors accumulate thermal electrons at a rate of roughly 4 electrons per second per pixel at 25°C. With every approximately 6°C decrease in temperature, the dark current is reduced by half. Where a 10-minute exposure might generate 2400 thermal electrons at 25°C, it will produce only about 10 at -25°C. This is a very small number when compared to the CCD read noise and pixel full well capacity.
The sensor employs a true two-phase charge transfer technology with a transparent gate that significantly increases optical response compared to traditional front-illuminated full-frame sensors.
CCD Cooler Subsystem
Key in the compact design of the 600 Series cameras is a very efficient custom 2-stage thermoelectric cooler (TEC) subsystem. Intelligent, programmable cooling fans are integrated into the rear of the camera body to remove the heat generated by the cooler. Typically, forced air cooling lowers the regulated CCD temperature by up to 45°C below ambient utilizing 85% power. Tight +/- 0.1°C temperature regulation is maintained at temperature settings of 10°C below ambient and lower. A slim liquid heat exchanger can be attached to the rear of the camera body to increase the cooling further, up to 55°C below the temperature of the circulating fluid.
The cooled CCD image sensor is positioned in a hermetically sealed environmental chamber covered with an anti-reflection coated precision optical window. The chamber is purged with an ultra-dry noble gas to increase heat conduction and eliminate the possibility of frost forming inside the chamber. To extend the useful period before re-purging is required, a user-rechargeable microsieve desiccant is employed to scavenge water molecules that enter the chamber. It is located behind a sub-micron, gas-permeable membrane to prevent particulate contamination of the CCD chamber.
Cooling and Dark Current
Effective cooling of the CCD image sensor is essential for long-exposure imaging, especially in astronomy. Thermally generated electrons accumulate in the pixels over time and compete with the photo-electrons that make up the image. This accumulation of thermal electrons is known as ‘dark current’. It lowers the dynamic range of the sensor and reduces the signal-to-noise ratio. Eventually, the thermally generated electrons will swamp the image.
Fortunately, dark current can be reduced dramatically by cooling the CCD. Kodak CCD sensors accumulate thermal electrons at a rate of roughly 4 electrons per second per pixel at 25°C. With every 6.3°C decrease in temperature, the dark current is reduced by half. Where a 10-minute exposure might generate 2400 thermal electrons at 25°C, it will produce only about 10 at -25°C. This is a very small number when compared to the CCD read noise and pixel full well capacity.
Electronic Shutter
The QSI 660 utilizes the electronic shutter built into the Sony ICX694 CCD image sensor to control exposures. Shutter timing is very precise and can range from as short as 100 microseconds up to 240 minutes. The very fast-acting shutter is possible due to two key features of the interline transfer architecture.
Any existing electrons can be removed from the pixels instantly with a single electronic pulse, beginning the exposure.
After the specified exposure duration, the entire image field can be instantaneously moved into a light-shielded holding area on the CCD. The image is then read out at the normal rate without being contaminated by any light still illuminating the CCD surface.
Mechanical Shutter
The QSI 660wsg-8 model incorporates the optional internal, even-illumination mechanical shutter in the ‘mid-size’ camera body configuration. When operating with an interline transfer CCD, the mechanical shutter is not used to actually make the exposure. This is still the responsibility of the electronic shutter. The mechanical shutter is employed to cover the CCD and simplify the creation of Dark and Bias frames for subsequent image processing.
Filter Wheel
The Model 660wsg-8 adds an internal eight-position filter wheel to the camera in a ‘full-size’ camera body. Even with the large 6.1mp sensor, the short back focus and close spacing provided by the internal color filter wheel allow the 660wsg-8 to work even with optics as fast as f/2.8 with no vignetting. The filter wheel accepts any standard threaded 1.25" or unmounted 31mm filters.
The filter wheel can be easily removed and replaced to change or clean the glass filters. Additional filter wheels can be purchased allowing quick interchange of different filter set configurations.
Integrated Guider Port
Selecting the best guiding solution for deep-sky imaging has always required a compromise. The available Integrated Guider Port (IGP) solves many of the problems associated with existing guiding solutions.
The Right Guiding Solution
Guiding with a separate guide scope provides the most flexibility, but differential flexure can be an issue, especially with long focal length scopes. With an internal guide chip, you’re forced to guide with light through your filters and you can’t guide at all while the shutter is closed or an image is being downloaded. This is especially problematic for narrowband imagers. To get around those issues, you could add an external off-axis guider, but a traditional OAG can add an inch or more of back focus plus more weight, and two new mounting surfaces that need to be held rigidly.
Guide with Light From in Front of the Filter Wheel
The QSI 660wsg-8 model solves the problems with other guiding solutions by integrating a Precision Off-Axis Guider directly into the camera body with the pick-off prism positioned in front of the integrated color filter wheel – right where it belongs.
Never Struggle With Finding a Guide Star
One of the main challenges when using a camera with an internal guide chip is to find a star bright enough to guide by within the limited field of view of the internal guide sensor. When shooting through red, green or blue filters, a small percentage of the available light is blocked by the filter and not transmitted to the internal guider chip, guaranteeing lower signal-to-noise stars for guiding. This problem is compounded with narrowband filters where as little as 1% of the total light from a star reaches the guide chip. By positioning the pick-off prism in front of the filters, you always have all the star’s light available for guiding.
Integrated Guide Port Supports Fast Optical Systems
By integrating the Off-Axis Guider into the camera, we’re able to position the pick-off prism very close to the internal filter wheel adding minimal back focus and eliminating any possibility of flexure or rotation compared to a traditional OAG. The large ½” square pick-off prism is optimally positioned close to the internal filter wheel, supporting the use of guide cameras with large sensors, while preventing any vignetting of the main sensor even with very fast optical systems.
Flexible Guide Camera Options
The Integrated Guide Port (IGP) built into QSI 660wsg-8 model is designed to support any camera with 12.5mm of back focus or less that can be attached using C-mount or T-mount threads. Many cameras are designed with 12.5mm of back focus to be compatible with CS-mount lenses. CS-mount lenses use the same thread as C-mount (1" x 32tpi) but with 12.5mm of back focus as opposed to 17.5mm for C-mount.
Easy, Rigid Guide Camera Focusing
The guide camera attaches to the WSG using a C-mount or T-mount threaded adapter (specified at time of order). The threaded adapter sits on top of the focus ring and allows the guide camera to be rotated to any position. The focus ring threads onto the focus base to allow 3mm of travel when focusing the guide camera. Once focus is achieved, the focus ring is locked with a set screw. The guide camera can still be rotated manually if desired without changing the focus. The end result is a rigid, easily focused guide camera that will not move or flex while your mount tracks the apparent motion of the night sky.
USB Interface
All QSI 600 Series cameras utilize High-Speed USB 2.0 port (USB 1.1 compatible) for connection to the host computer and imaging application software. Read and transfer time for an entire 6.1mp image frame is typically approximately one second in High-Speed mode and less than 12 seconds in High-Quality mode. The frame rate can be further increased by reading just a portion of the image (ROI) or with flexible on-chip binning.
Guider/Control Port
A four-channel optically isolated control port is accessible through a standard 6-pin modular connector. The signal pin-out is compatible with most modern telescope mount drive correctors and is intended to be used for telescope guiding under MaxIm/DL and CCDSoft. The outputs can also be used for other control purposes when developing your own applications with the 600 Series ActiveX software development toolkit. The outputs are common emitter, and open-collector, and can sink up to 50ma. The maximum voltage should not exceed 50v.
Power Requirements
One of the defining features of the 600 Series cameras is power efficiency. A fully configured 640ws camera operates from a single 12v DC supply and consumes less than 24 watts at full cooling, with both fans at maximum and the filter wheel moving. Other camera model configurations have power consumption as low as 5 watts. Included with each camera is an approved 12-volt DC power supply with an input voltage range of 90-240V, 50-60HZ.
Notification
Both visual and audible notification is built into all 600 Series cameras. A multi-color LED status display provides a visual indication of the various states of camera operation. The behavior of the indicator is configurable and can be disabled by the user command. A unique internal beeper provides audible feedback on camera operation and status. Like the visual display, the beeper can be configured and disabled by the user.
SKU: qsi660wsg-8