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[Pic Mike Dryland] |
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Tony (L) explains a webcam adapted for astrophotography [pic Mike Dryland] |
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Flamsteed Astronomy Society |
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“Getting started in Astrophotography” workshop with Tony Sizer — April 20, 2009 |
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page 3 of 3 |
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CCD Imagers Purpose-made CCD imaging cameras are now available at all prices from about £100/150 upwards. They are offered by most major telescope manufacturers and several specialists. The cheaper types are based on modified webcams. At the expensive end, CCD imagers have cooling systems to reduce the electronic noise which would otherwise compete with low-level signals from very dim objects. Like webcams, CCD imagers must be connected to a laptop or PC to control them and store the images. Imaging deep-sky objects will be best done with a webcam or CCD imager. Software Much astrophotography is now done under software control from a laptop or PC. Webcams and CCD imagers require software control, and DSLRs can also be controlled via a USB connection. Software control provides a significant improvement to overcoming the problems of ‘seeing’ — atmospheric disturbance. Movements in the air cause the magnified image to appear to jump and shimmer. With film photography and long-exposure digital imaging, this would lead to blurred images. Under software control the answer is to take many short-exposure images (sometimes hundreds of images), maybe 0.2 or 0.1 secs duration each, then process them afterwards to add them all together. The free software “Registax” is a favourite tool to do this. Other software tools are used to help control and process the images — IRIS to subtract ‘dark frames’ and eliminate constant noise in the CCD chip; K3CCD tools to control the webcam and generate .avi format images for Registax processing. Imaging will soon produce gigabytes of data which might overwhelm less capable PCs. Telescope and Mount As with visual observing, the choice of telescope depends on the subject to be imaged. For lunar and planetary work, short focal length refractors, like those by Williams, are becoming popular and are very good value. A decent telescope mount is needed for astro-photography beyond the most elementary steps. Either a good equatorial mount with a polar-finding scope and smooth motor drives, or a goto mount possibly with auto-tracking software. An electric focuser will also be helpful. With remote software control for the focus, mount, and webcam or CCD, there is the possibility of observing from the comfort of indoors while controlling the kit through long extension leads! Brings new meaning to the term “arm-chair astronomer”. MRD
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Saturn, April 10, 2006 10-in reflector and Meade LPI camera by Tony Sizer |
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Mars, October 23, 2005 7-in Mak and Philips TouCam, by Malcolm Porter |
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Comet C/2006 P1 McNaught, Jan 10, 2007 Canon Rebel with 100-300mm lens, 0.5 secs by Francisco Diego |
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[Pic Mike Dryland] |