When the first astronomical CCD cameras, intended for amateur astronomers, were introduced, they offered tremendous quantum efficiency, showing deep space objects in a fraction of exposure time compared to film emulsion (plus huge number of other advantages, like digital image processing etc.). But they suffered from one important flaw — limited sensor area compared to film and thus limited field of view.

This situation inverted these days. Cameras like G4-16000 or G4-9000 offer CCD sensor measuring 37 × 37mm, surpassing the typical film frame area by 50%. But it is really not easy to put together optics, capable to cover such giant sensor. And CCDs do not help the situation with its ability to precisely focus images (we have immediate feedback while focusing) and to digitally process them so every optical aberration is clearly visible. Newtonian telescopes need huge secondary mirrors, 3" focusers and coma-correctors and still fast setups suffer from vignetting in the edges of the field. ED and APO refractors also need 3" focusers and field flatteners else large sensors cannot be used without significant compromises.

Here comes the G3-16200 camera with the new KAF-16200 CCD sensor. While other astronomical cameras use CCD chips primarily designed for different application fields, KAF-16200 has “astronomy imaging” stated as the primary application in its birth certificate.

• Sensor dimensions 27.2 × 21.8 mm (35 mm diagonal) are designed for 2" focusers and correctors, often using M42 or M48 threads.

• Sensor aspect ratio 5:4 is very close to square to optimally fit aberration-free circle within the field of view, but also prolonged enough to allow optimal composition of frame, required by astro-imagers.

• Sensor can be used with 2" filters (od unmounted D50mm filters), which are more common and affordable compared to square 50 × 50mm filters. Also more filters can fit into the same filter wheel and the G3 design allow usage of internal filter wheel (the G4 cameras can use external filter wheels only, as the 50 × 50mm filters are too big to fit into camera head).

• 6 × 6μm pixels perfectly correspond to the typical focal lengths of amateur telescopes (between 50 and 150cm). Smaller pixels limit dynamic range and sensitivity at no added value, because resolution is limited by seeing (air turbulences) and optics, rather than by pixel size. At the same time greater pixels could provide under-sampled images if optics is good, mount perfectly tracks the stars and seeing is above average.

• Read noise around 10e-RMS is well beyond the sky background noise in the case of long exposures, even if the very best narrow-band filters are used (no to mention standard RGB filters).

• Dark current below 0.1 e-/s/px at 0 °C allows very long exposures, providing the sensor is used in camera allowing for proper cooling (like the G3-16200).

• Quantum efficiency reaching 60% surpasses the QE of very popular KAF-8300 CCD and is almost identical to e.g. KAF-16803. So it definitely allows capturing of stunning astrophotographs.

The G3-16200 camera continue in the tradition of Gx astronomical cameras, used for cutting-edge science as well as for the best astronomical images by professional and amateur astronomers all over the world. The G3 system contains models with internal or external filter wheels, wide variety of telescope adapters, off-axis guiding adapters, USB and Ethernet interfaces etc.

G3-16200 cameras are supported in the latest SIPS version 2.4 and newer and in the ASCOM drivers version 3 and newer.

For details and technical specification, download the G3 Camera User's Guide or visit the G3 camera description.