|The problem |
The popular and excellent Philips ToUcam and its successor, the SPC900NC, are now no longer available as new items, though you may still be able to get them on eBay. If so, they are well worth having and are superior to most webcams currently available. This is because they contain CCD chips rather than less-sensitive CMOS chips.
The ToUcam had a lens which could be easily unscrewed and replaced by a 1¼-inch adapter which was readily available from a number of suppliers for its 12 mm x 0.5 mm thread. The SPC900NC had the same thread though the lens was less easy to remove, but it was still an easy job.
Imaging with the ToUcam was therefore a simple matter of focusing the telescope, ideally using an eyepiece with a graticule and with a parfocal ring, then swapped it for the ToUcam the object would be in the centre of the field of view and close to focus.
I suspect that the Celestron NexImage uses the same chip as the ToUcam. It is considerably more expensive though it includes the adapter. Even so, it is lower cost than the purpose-built planetary imaging cameras described below ($159/£134). Stocks are available from David Hinds in the UK as well as from the States as of March 2009. Vista drivers are available.
Webcams are cheap to buy and still give some sort of a result, particularly on the Moon. So here is an account of webcams I have tried and the results.
The cheapest webcams available from PC World and Tesco look identical and cost around £5. I tried the PC World PCL 100K model (right). The lens does in fact unscrew and has the same 12 mm 0.5 mm pitch thread as a standard ToUcam adapter, though the adapter requires a long thread to fit. The 'on' LED needs sticky tape over it when used for astro-imaging.
Results with this camera were not bad considering its low cost. This picture of Petavius was made using an undriven 70 mm f/10 refractor, using just a few frames. However, the colour balance was hard to control.
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