The Art of Astrophotography by Ian Morison

Author:Ian Morison [Morison, Ian]
Language: eng
Format: azw3, pdf
Publisher: Cambridge University Press
Published: 2017-02-01T16:00:00+00:00

Figure 19.1 The PrimaLuce Lab 700Da cooled sensor DSLR camera

The alternative is to purchase a custom made astronomical camera incorporating a colour APSC sensor. The lowest cost of these OSC cameras currently on the market is the QHY QHY8L costing around £1000 as shown in Figure 19.2. The camera uses a 6 megapixel Sony sensor employing 7.8 micron square pixels and, most importantly, incorporates ‘set point cooling’ to cool the sensor to a specified temperature such as −20° Celsius. This makes the taking of dark frames at the same sensor temperature as the light frames far easier. The camera uses 16-bit digitisation and provides for 2×2 and 4×4 (monochrome only) binning modes. The 4×4 mode, which averages over 16 pixels, is significantly more sensitive and is used for rapid initial alignment on the selected object. The sensor is mounted in a slim body just 63 mm across, so making it perfect for use with a ‘HyperStar’ imaging system when the camera is mounted in the centre of the corrector plate of a Schmidt–Cassegrain telescope. To achieve this, the multiple power supplies required for the sensor electronics and Peltier cooling system are contained in a small separate unit connected to the camera with a multi-core cable. This is powered by a supplied mains adapter or 12 volt battery taking up to 4 amps current. As seen in Figure 19.2, the USB2 type B and power supply sockets are at the rear of the camera. As is often found with the USB2 type B connector, its placement in the socket of the QHY8L is not very secure. To overcome this problem, as also seen in Figure 19.2, a bracket (made using 3D printing) is supplied to mount on the camera in order to hold the connectors tightly in place. At somewhat greater cost, QHY manufacture a 10 megapixel version to give increased resolution. The ability to use the monochrome binning modes for initial alignment on faint objects makes these cooled CCD colour cameras – and those made by other manufactures such as the SBIG STF-8300C (which is the colour version of the STF-8300M monochrome camera that will be discussed in Chapter 20) – somewhat more practical than modified DSLR cameras. Many employ the rather smaller (17.96 × 13.52mm), 8 megapixel, Kodak KAH-8300 CCD array, which has superb low noise characteristics. The Moravian Instruments G2-8300 Colour CCD Camera has a very similar specification as does the Atik camera’s 383L+.

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