Almost all beginners want a colour camera and the attraction of colour images is obvious. Unfortunately, colour imaging comes at a cost in CCD performance, and you should be aware of this before making a decision. There are two common techniques used to create true-colour images. One of these is the classic ‘Tri-Colour’ technique of taking three images through red, green and blue filters and then combining the results into a single colour frame, using ‘Photoshop’ or a similar program. This method is used with a mono camera and so you can swap between colour and mono imaging at will, but you need a set of good quality colour filters and a filter wheel or holder is essential. You also must use at least three sequential exposures to capture the data and so it may be difficult to create a good image of moving objects, such as comets and planets. On the positive side, this technique will not reduce the resolution of your images and you have maximum flexibility to use any filters that you choose – or none at all.
The second option is to use a ‘One-shot’ colour camera, such as the SXVF-H9C or SXVF-M25C. This is quite a lot easier than ‘tri-colour’, as you capture all three colours in a single exposure and there is no need to register the RGB images together to create the final picture. A filter wheel is not necessary, although an ‘infrared blocking filter’ might be found to improve the colour rendering of the results. On the negative side, your CCD is permanently filtered and so there is some loss of sensitivity (longer exposure times will be needed, compared with an unfiltered mono CCD) and there is a small loss of image resolution. Despite the filter matrix, it is still possible to take narrow-band (H-alpha, OIII etc.) images with a one-shot camera, so the limitations are not as severe as some experts might try to tell you.
Please note that our ‘One-shot’ colour cameras do NOT download a colour picture directly. The filter data is encoded in a mono image and this is extracted by software after image capture. This gives the best possible results, as the mono image can be fully ‘calibrated’ before colour extraction, unlike colour video cameras etc.
An important fact that you should note is that light pollution can cause major colour balance and gradient issues with one-shot colour cameras. If you image from a light polluted location, then you should seriously consider following the mono camera option. You can then use narrow band filters to combat the light pollution and achieve results that would be very difficult to obtain with a colour imager. A light pollution blocking filter (e.g. IDAS) will help a lot, but a truly dark sky is the best for colour imaging.