QSI  Home Page

QSI 516
  Home > 500 Series > QSI 516

  • Full-frame 1.6 megapixel KAF-1603 sensor
  • Low noise, wide dynamic range
  • Up to 45C CCD cooling
  • Built-in mechanical shutter
  • Available internal 5-position color filter wheel
  • Available integral Off-Axis Guider (OAG)>>
  • Available MaxIm LE camera control and image processing software
  • CCDSoft and MaxIm DL Drivers
  • ASCOM-compatible Windows API
  • Linux drivers and API 520i

QSI 516 Scientific
Cooled CCD Camera

The standard 516 model camera employs a 1.6 megapixel Kodak Enhanced Response full-frame CCD image sensor with microlens technology. The high quantum efficiency, wide dynamic range and low noise performance make the 516 ideally suited to a broad range of demanding astronomical, scientific and industrial imaging applications.
The 500 series sets a new benchmark for compact design and power efficiency in a high performance, full-featured scientific CCD camera. With optional features and upgradeability, the 516 can be tailored to fit your needs today and in the future.

The 516 camera system is supported by industry leading image acquisition software and development tools are available for creating custom Windows or Linux imaging applications.

The QSI 516wsg is now available with an integral Off-Axis Guider allowing you to guide using the light from your main telescope while picking off the light from the guide star in front of the filters.
Learn more about the available built-in OAG>>

Starting at POA  
Configure Camera

"The results speak for themselves."

Read the full review of the QSI 516ws
from AstroPhoto Insight (pdf) 1.9mb >>

Refined Design
High Performance CCD Image Sensor
Leading Edge Technical Performance
Efficient, Low Power CCD Sensor Cooling
Compact Shutter and Filter Wheel
Innovative Integrated Off-Axis Guider
Connectivity and Notification
Extensive Software Support
Innovative, Aesthetic Body Design

Small enough to practically hide behind a CD-ROM, the medium format QSI 500 Series family sets new standards for full-featured, high performance scientific CCD cameras. The striking appearance, refined design and superior fit and finish only hint at the advanced technical performance lurking inside. Some have described it as a work of art.

A defining feature of the 500 Series is the flexible design that permits three progressively configured body styles with a minimal impact on overall size. The relative sizes of the three body configurations, Slim, Medium, and Full, can be seen in the image to the right. A camera's body size depends on the internal features installed. The Slim body is the thinnest version and can be used with CCDs incorporating an electronic shutter. The Medium body provides addition space for an internal mechanical shutter. The Full body allows the installation of both the shutter and a five position filter wheel with interchangeable filters.

Engineered with extensive use of sophisticated CAD-CAM design tools, the 500 Series is CNC machined from aircraft grade aluminum alloy. The finely finished anodized body components are assembled with corrosion resistant stainless steel hardware throughout.

Small, Light-Weight and Thin

The 500 Series is designed to support image sensors with a maximum diagonal measurement of 22mm, characterizing the family as Medium Format cameras. For this class of camera they are surprisingly compact. At just 4.45" square, the Slim body camera is just 1.68" deep, occupying less than 30 cubic inches and weighing in at under 26 ounces. Even a Full body camera with shutter and color filter wheel is only 2.5" deep and a mere 40 ounces. In fact, the small footprint is the practical limit for a camera with a 5 position filter wheel using standard 1.25" interchangeable filters.

Keeping the depth of the camera to a minimum was an early design goal. Not only is backfocus minimized, but the camera moment-arm is reduced resulting in greater stability. Tight spaces, like through the forks of an SCT telescope, are no longer a problem. The shutter and filter wheel were placed inside the body, very close to the image sensor reducing backfocus and overall depth. The motion control electronics are actually buried in the 0.12" thick shutter/filter mounting plate to reduce depth further. Pulling the cooling fans and heatsinks into the body resulted in another significant reduction in depth. Finally, having all electrical cables and the optional liquid heat exchanger recirculation hoses exit the body in the same direction and perpendicular to the optical axis insured an interference-free fit in tight spaces.

More Camera and Application Photos >>

1.6 Megapixel CCD Image Sensor

The standard 516 model camera employs a Kodak KAF-1603ME 1.6 megapixel Enhanced Response full-frame CCD image sensor with microlens technology. The KAF-1603ME sensor has a photoactive array of 1536W x 1024H pixels. It has excellent quantum efficiency between 350nm and 1000nm with significant enhancement at the blue end of the spectrum. Low dark current and high pixel charge capacity result in a dynamic range exceeding 76db. 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. Micro lenses cover the surface of the CCD to focus the light through the transparent gate to further increase optical response. See the Specifications tab for more detail.

Two other CCD configurations are optionally available. The KAF-1603E image sensor does not include micro lenses but is otherwise identical to the standard image sensor. A KAF-1602LE with anti-blooming protection is also available. Anti-blooming prevents charge spillover into adjacent pixels under high illumination. This protection technology consumes about 30% of the pixel area with a proportional decrease in saturation signal and quantum efficiency. The chart above illustrates the difference in quantum efficiency between these three CCD imager sensors.

All three types of CCD image senor are available as either Class 1, or Class 2. A Class 1 imager has very stringent limits on possible pixel defects while a Class 2 relaxes these limits somewhat for a lower cost. All 516 cameras employ a Class 2 CCD imager as standard and can be upgraded to a Class 1 at the time of purchase.

  High Performance Design

"The QSI 500 Series scientific camera family was designed from the ground up to attain the highest possible imaging performance from Kodak's KAF and KAI CCD image sensors."

  • Sophisticated mixed-signal design practices are utilized throughout the camera. This permits a very compact design while eliminating interference from conducted and radiated noise. All of the many internal clock and bias voltages are set via high precision Digital to Analog Converters (DACs) under computer control, allowing automated optimization during manufacture. ROHS compliant multi-layer circuit boards and surface-mount components are used exclusively. A unique circuit board stacking methodology eliminates interconnecting wires that could reduce reliability.
  • Arguably, the most important aspect of a CCD camera design is the video processing subsystem. This is where almost all of the camera's performance characteristics are established. The 500 Series video processing begins with a very low noise, precision preamp to accurately amplify the microvolt level pixel signal from the CCD image sensor. This signal is then processed through a Correlated Double Sampler (CDS) to reduce temporal read noise in the pixel signal. Subsequent signal conditioning then feeds the pixel level to a high-speed, precision 16 bit Analog to Digital Converter (ADC) where it is converted to a digital value between 0 and 65535.

    The Read Noise contributed by this entire subsystem is exceedingly small. So small in fact, that it is virtually undetectable, contributing less than 1/30 of the combined read noise of a typical KAF image sensor. The low read noise and carefully chosen camera gain yield excellent Dynamic Range. Linearity is also outstanding, limited only by the CCD image sensor itself.
  • An internal pipelined data architecture with a large FIFO memory buffer is employed to achieve a constant 500,000 pixel/second read rate from the CCD. The multi-controller design effectively decouples the camera pixel read operation from the USB transfer process while ensuring maximum throughput.
  • A carefully designed and isolated switching power supply generates all of the voltages needed to operate the camera from a single 12VDC power source. Low noise design practices and advanced filtering techniques completely eliminate any measurable impact on camera noise performance.
  • All significant performance characteristics, including Linearity, Read Noise, and Photon Transfer (Gain), are tested and confirmed during manufacture. Each camera's timing and voltages are carefully set during manufacture to ensure maximum Charge Transfer Efficiency, and to minimize charge injection and other secondary noise sources. QSI's exclusive ResearchSpec� profiling ensures optimal performance in every camera.

CCD Cooler Subsystem
Key in the compact design of the 500 Series cameras is a very efficient 12 watt thermoelectric CCD cooler 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 38�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 45�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 minimize the frost point and heat conduction. 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, 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 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 KAF 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 of 15 electrons and the pixel capacity of 100,000 electrons. At -35�C, a 1 hour exposure will generate less than 20 thermal electrons per pixel!

Shutter and Filter Subsystem
The 500 Series achieves its compact size and unique configuration flexibility though an innovative shutter/filter subsystem. Both the mechanical shutter and filter wheel can be installed internally while keeping the growth of the camera dimensions at a minimum. This results in minimal loss of backfocus as these features are added. The compact design also reduces vignetting with fast optical systems.  


The Model 516s camera incorporates the internal mechanical shutter in the 'mid-size' camera body configuration . The shutter is not only used for timing exposures, but can be left closed to produce 'dark frames' for subsequent image processing. Exposures can be as short as 0.03 seconds or as long as 240 minutes.

Filter Wheel  

The Model 516ws adds an internal five position filter wheel to the camera in a 'full-size' camera body. The filter wheel accepts any standard 1.25" filter and can be purchased with various filter configurations. The filter wheel can easily be removed and replaced to change or clean the glass filters. Additional filter wheels can be purchased allowing quick interchange of different filter set configurations. (Note how the RGB filters reflect the complimentary color in the picture at the right.)

LRGB Filter Set
Astronomik Type IIc LRGB filters are the standard filters available with the 504ws camera (filter sets from other manufacturers are available by request.) The Astronomik filters are optimized for astronomical color imaging and the bandpass is designed to accurately match the color sensitivity of the human eye. Infrared cutoff down to 1150nm is integrated into each filer eliminating the need for an extra IR filter. These thickness-matched filters are par-focal with excellent transmission to nearly 100%. The chart below illustrates the bandpass characteristics of each filter.

Integral Off-Axis Guider
QSI 500 wsg Selecting the best guiding solution has always required a compromise. The available, integral off-axis guider (OAG) 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.

QSI 500wsg Prism closeup

Guide with Light From
in Front of the Filter Wheel

The QSI 500 Series "wsg" models 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 intenal guide sensor. When shooting through red, green or blue filters, ⅔ 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 OAG 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 backfocus 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 Off-Axis Guider (OAG) built into 500 Series "wsg" models 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.

Click here for a list of guide cameras known to be compatible >>

Easy, Rigid Guide Camera Focusing

QSI 500 wsg Adapters

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.

The connector panel, shown above, is thoughtfully recessed into the body of the camera for protection and provides access for all external connections. The two threaded holes on the back of the body are used to attach an optional cable restraint system to support the electrical connections as well as the recirculation hoses if the liquid heat exchanger is employed.

USB Interface

All 500 Series cameras utilize a standard USB 2.0 (USB 1.1 compatible) port for connection to the host computer and imaging application software. Read and transfer time for an entire 1536x1024 image frame is typically less than four seconds.

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 500 Series ActiveX software development toolkit. The outputs are common emitter, open-collector and can sink up to 50ma. The maximum voltage should not exceed 50v.

Power Requirements

One of the defining features of the 500 Series cameras is power efficiency. A fully configured 516 camera operates from a single 12v DC supply and only consumes 18 watts at full cooling, with both fans at maximum and the filter wheel moving. Other camera model configurations have power consumption as low as 3.5 watts. Included with each camera is an approved 12 volt DC power supply with an input voltage range of 90-240V, 50-60HZ.


Both visual and audible notification is built into all 500 Series cameras. A multi-color LED status display provides visual indication of the various states of camera operation. The behavior of the indicator is configurable and can be disabled by user command. A unique internal beeper provides audible feedback of camera operation and status. Like the visual display, the beeper can be configured and disabled by the user.

Comprehensive Software Support

Every 500 Series camera is accompanied by a collection of software applications and tools that allow you to begin imaging immediately or develop custom camera control applications to precisely match your requirements.

MaxIm LE

MaxIm LE is based on the award winning MaxIm DL version 4.5 from Diffraction Limited providing the fastest and easiest way to image the night sky. All QSI Series 500 cameras are supported for imaging and auto-guiding, plus most popular guider cameras are supported as well. MaxIm LE is available with any 500 Series camera. You can upgrade to MaxIm DL/CCD for an attractive price at the time of purchase. Details >>

Drivers for Software Bisque's CCDSoft

Realizing that one shoe doesn't fit all, QSI also supplies the necessary drivers for CCDSoft, the popular Image Processing and Camera Control Software from Software Bisque.

Windows Custom Application Development

QSI provides an ASCOM-compatible API (Application Programming Interface) enabling users to write their own custom camera control applications. The camera control API is an automation component that communicates with the camera device driver and exports a COM automation interface. COM automation provides an interface which Microsoft Office, VB, VBA, C++, and other Windows applications can use to control the camera. The API is available as part of the QSI Software Development Kit (SDK), available for download from the QSI website.

ASCOM Learn more about the ASCOM Initiative.

Linux Custom Application Development

QSI provides a camera control C++ API for Linux users on Intel x86-compatible platforms. The API provides full camera control and image capture capabilities via the USB interface. The API is implemented as a shared library providing an easy to use camera object that exposes all of the features and capabilities of the camera. It is well suited for both simple scripting, and more sophisticated imaging application development.

View complete 500 Series Software details >>.

Field Upgradeable Firmware

All 500 Series cameras can be upgraded to the latest firmware in the field. The latest firmware is always available for download from the QSI Software page. QSI supplies a simple fail-safe Updater application that handles all the details.

Model 516 Available CCD Image Sensor Specifications
Feature Standard Optional Optional
CCD Manufacturer & Model     Kodak KAF-1603ME        Kodak KAF-1603E        Kodak KAF-1602LE
CCD Architecture Full Frame Full Frame Full Frame
     Blue Enhanced Yes Yes No
     Microlens Yes No No
     Anti-blooming No No Yes
300x suppression
Imager Size: (WxH) 13.8mm x 9.2mm 13.8mm x 9.2mm 13.8mm x 9.2mm
Pixel Array (WxH): 1552x1032 total pixels,
1536x1024 active (visible)
1552x1032 total pixels,
1536x1024 active (visible)
1552x1032 total pixels,
1536x1024 active (visible)
Pixel Size: 9µm x 9µm 9µm x 9µm 9µm x 9µm
  Typical Values
Pixel Full Well Depth 100,000 electrons 100,000 electrons 50,000 electrons
Absolute Quantum Efficiency Peak: 77%
400nm: 45%
Peak: 65%
400nm: 30%
Peak: 35%
400nm: 20%
Pixel Dark Current <1.0 electron per second at 0�C
<0.1 electron per second at -25�C
Dark Current Doubling 6.3� C 6.3� C 6.3� C
Intrinsic Read Noise 15 electrons RMS 15 electrons RMS 15 electrons RMS
Dynamic Range 76db 76db 70db
Charge Transfer Efficiency >0.99999 >0.99999 >0.99999
Manufacturer's CCD Imager Specifications
KAF-1603E/ME (PDF) KAF-1602LE (PDF)

Model 516 Camera Specifications
  (See additional 516wsg specifications>>)

Feature Model 516s Model 516ws
Standard CCD Image Sensor KAF-1603ME KAF-1603ME
Shutter Mechanical, exposure range: 0.03 seconds to 240 minutes
Internal Color Filter Wheel No Yes - 5 Position, 1.25" std filters
Camera Body Configuration Medium
Dimensions W4.45” x H4.45” x D2.00”
(add 0.23" for T-Mount)
W4.45” x H4.45” x D2.50”
(add 0.23" for T-Mount)
Weight, without Nosepiece 34 oz.  /  950g 40 oz.  /  1120g
Optical Back Focus
(without Filters in path)
0.90" with T mounting adapter
0.68" with C mounting adapter
0.68" w/o mounting adapter
1.40" with T mounting adapter
1.18" with C mounting adapter
1.18" w/o mounting adapter
Thermoelectric CCD Cooling Temperature regulation +/- 0.1�C, @ 0�C  to -40�C CCD temperature
     In free air, Fans @ Full Speed Typically 38�C below ambient air with 85% cooling power
     With Opt Liquid Cooling - Fans Off Typically 45�C below circulating liquid with 85% cooling power
(adds 0.75" to camera depth)
Cooling Fan Control Intelligent, user configurable
Camera Gain 2.6 electrons per ADU
Digital Resolution 16 bits
Total System Read Noise Typically <15 electrons RMS (CCD specification limited)
Pixel Dark Current <1.0 electron per second at 0�C
<0.1 electron per second at -25�C
Full Image Read and Download Time Typically <4 seconds (host computer dependent)
Binning Modes Symmetrical on-chip 2x2 and 3x3, user selectable
Status and Notification User configurable multi-color LED status indicator and multifunction
audible beeper. Over-temperature and high/low voltage alarms.
Power Consumption 12v, 1.5A (18 watts) at max cooling, max fans and filter moving
(25 AC watts max with included 90-240V AC power supply)
Operating Environment Temperature: -20�C to 30�C, Humidity: 10% to 90% non-condensing
Computer Connectivity USB 2.0 (USB 1.1 compatible)
Other Ports Optically isolated 4 channel control port for telescope guiding
or other application specific control
T Mounting Adapter Standard adapter - T-Thread, 42mm x .75mm
C Mounting Adapter
(1" x 32TPI)
Optional, C-Mount lens focus
compatible (17.5mm backfocus)
Optional, for non-lens adapters and
accessories (standard C-Mount lens
does not reach focus)
Nosepiece Standard, T-Adapter to 2" nosepiece
Optional, T-Adapter  to 1.25" nosepiece
The following standard items are included
with every QSI 516s and ws camera:

    (See 516wsg standard items>>)
  • T-Mount Camera Adapter*
  • T-Mount Adapter Cover*
  • T-Mount to 2" Nosepiece*
  • 12VDC / 90-240VAC power supply
  • 10' USB 2.0 Interface Cable
  • 10' Standard Guider Cable
  • QSI Software Installation CDROM
  • Drivers for MaxIm DL/CCD and CCDSoft
  • ActiveX Developer's Toolkit
  • Custom Fit Pelican Storage Case

View all Accessories >>
* Other options are available at
the time of purchase. See Configure Camera page...

Options and Accessories
MaxIm DL/CCD Upgrade
Upgrade to MaxIm DL/CCD at time of camera purchase and save substantially over regular retail price.
Liquid Heat Exchanger
Provides up to 10�C additional CCD image sensor cooling. For use in warm weather conditions.
Color Filter Wheel
Replacement five position color filter wheel. Ideal for quick change of additional filter sets. Accepts all standard 1.25" filters.
Recirculating Pump
Water recirculating pump for use with liquid heat exchanger - 115VAC. Twenty five feet of clear vinyl tubing included.
1.25" Nosepiece
1.25" nosepiece to T-Mount adapter. Optional
SLR Lens Adapter
Designed for full-size QSI "ws" cameras with T-Mount adapter. Available for Canon EOS and Nikon F lenses.
2" Nosepiece
2" nosepiece to T-Mount adapter. Standard on all 500 Series QSI cameras.
T-Mount Adapter
T-Mount adapter plate. Standard on all 500 Series QSI cameras.
Power Supply
Replacement 12v DC power supply for all 500 Series cameras. Input: 90v-240v AC 50-60Hz.
C-Mount Type II Adapter
C-Mount Adapter plate. Fits all Medium body QSI 500 Series cameras.

 Shopping Help
 Privacy Policy
 Terms of Use
 Contact QSI
Copyright © Quantum Scientific Imaging. All Rights Reserved. Part of the SDI Group.