Celestron Nightscape 8300 CCD
A one-shot colour CCD camera based around a tried and tested imaging sensor, the Nightscape 8300 produces impressive images with natural colours and plenty of intricate detail
The Celestron Nightscape 8300 is a cooled, one-shot colour camera built around Kodak’s KAF 8300 CCD chip. The chip has already made a good impression in astrophotography, having been used in a range of established products.
There are a number of interesting facilities on the Nightscape 8300, including a hardware shutter that clicks out of the way when an exposure is being taken and a 32MB buffer memory to ensure the image is properly stored before being downloaded. The KAF 8300 sensor is large, approaching DSLR dimensions with its 8.3-megapixel array. But unlike a conventional DSLR, the Nightscape 8300 can cool its imaging chip to 20°C below ambient temperature, which helps keep noise to a minimum.
Infrared-blocking filters are often used to prevent pixel saturation at these wavelengths but they can be a problem in commercial DSLRs because they block some of the all-important hydrogen-alpha wavelength (656.28nm), which is predominant in emission nebulae. The Nightscape 8300 uses an infrared-blocking filter that’s hydrogen-alpha friendly and permits up to 94 per cent of this wavelength to pass through. By doing so it allows emission nebulae to be recorded with the correct colour balance and retains their intricate but tenuous detail.
Catching a tricky target
We tested the Nightscape 8300 on the North America Nebula, NGC 7000 – a huge region that resembles the shape of North America (hence its name). It’s filled with stars and hydrogen gas that glows in hydrogen-alpha, but capturing it can be hard because it’s so large; it measures a full 2° across.
We coupled the camera to a wide-field setup – a 2.6-inch refractor with a 0.63x focal reducer-flattener, giving us a focal length of 244mm (focal ratio of f/3.7). This provided an image scale capable of recording the entire nebula, with enough border space to give it some context. To perform the capture sequence we used the AstroFX control software that comes with the camera.
Like most colour-imaging devices, the Nightscape 8300 captures in monochrome through a matrix of tiny colour filters. The greyscale result is then interpreted using a special software routine that reinstates the full-colour image.
Crisp and colourful results
While taking our 300-second exposures the camera’s protective shutter could be heard opening and closing. This mechanical device is useful for taking dark frames, as you don’t have to cap the front of the telescope first. A request via AstroFX to take a dark frame simply instructs the camera to image without opening the shutter first.
The results were impressive. The nebula colour looked natural and there was plenty of detail in the shot. Star colours were also excellent. The cooled KAF-8300 sensor showed little noise.
The Nightscape 8300 is a good next step if you’ve been using a DSLR for astrophotography. Its pictures give less noise, better colour and respond better to hydrogen-alpha light than a DSLR. It’s also a good choice if you’re starting out in imaging thanks to the helpful AstroFX control software.
At the higher end, the Nightscape 8300 has to compete with mono CCD cameras with arguably better sensitivity. However, getting full-colour results with a mono CCD requires filters, which add to the cost and complexity. Some prefer this route as it gives greater control and flexibility, but the Nightscape 8300 can deliver the goods without the headaches. This is a capable camera that’s capable of producing stunning results.
The Nightscape 8300’s core is the Kodak KAF-8300, low-noise imaging chip. At full resolution it can record a 3,326x2,504 (8.3-megapixel) image that takes around 12 seconds to download. A region of interest (ROI) can be defined with presets for full, half or quarter frame; smaller ROIs are quicker to download. A small ROI around a star, for example, can generate rapidly repeating images for focusing.
A 2x2 binning mode makes four pixels work as one ‘super-pixel’. This increases sensitivity but limits the image to monochrome. Exposures can be from 0.001 seconds to 24 hours (2x2 binned), or 0.01 seconds to 24 hours (no binning). The Nightscape 8300’s sensor has a stated 33 per cent quantum efficiency in the blue and red part of the spectrum, rising to 40 per cent in the green. Images are output from the camera as 16-bit data saved in the FITS (Flexible Image Transport System) format. The AstroFX software can process and convert these files to other types.
Camera body - The Nightscape 8300’s body is roughly cylindrical. Normally used at the business end of a telescope, this solidly built unit can also be fitted to a Fastar compatible Schmidt-Cassegrain telescope, replacing the secondary to produce a very fast setup. Its body is rear-vented and T-threaded at the front. All the main electrical connectors, including 12V input, are located on the side.
AstroFx - The Nightscape 8300 is supplied with a control program called AstroFX, which guides you from image capture to the generation of your final masterpiece. AstroFX is well thought out, save for the slightly cumbersome floating control window. A supplied ASCOM driver allows the camera to be used with other image acquisition packages if you prefer.
Cooling - The camera has a regulated thermoelectric cooling system and fan to remove excess heat. Together, these allow the imaging sensor to be cooled to 20°C below ambient temperature. A cooler sensor means less noise from the already low-noise KAF-8300 sensor. The desired sensor temperature is set via software, and cooling is quick and efficient.
Mechanical shutter - The Nightscape 8300 has a mechanical shutter that helps keep dust out of the sensor cavity and provides a useful way to take dark-calibration frames. When the AstroFX software is instructed to take a dark frame, the sensor images with the shutter closed. This eliminates the need to manually fit the telescope’s lens cap.
Infrared-blocking filter - Commercial imaging chips can be quite sensitive to infrared light, which can lead to loss of definition and incorrect colour balance. DSLR manufacturers often fit an infrared-blocking filter, but this can also remove important hydrogen-alpha light. The Nightscape 8300 uses an infrared-blocking filter designed to be hydrogen-alpha friendly.
This review originally appeared in the October 2013 issue of BBC Sky at Night Magazine