ASTRO-IMAGING
18 SEPTEMBER 2008
The first meeting of the 2008/2009 Session of the ASG takes place at 7:30pm pm on Thursday 18 September, 2008 in Room R3.45, RoyalCollege, University of Strathclyde. Enter from Montrose Street.
We are delighted to welcome Dr Giles Hammond to talk about 'Webcams and CCTV Cameras: Affordable Imaging Tools for the Amateur Astronomer'.
The past ten years has seen a revolution in low cost astronomical imaging tools available to amateur astronomers. For example, the Charge Coupled Devices (CCD’s) found in the Philips SPC900NC webcam and the RF Concepts 1004X CCTV camera are identical to those used in high cost professional cameras from manufacturers such as Starlight Express. However, there are three areas in which these low cost cameras are inferior to their significantly higher cost professional rivals. Firstly, in their off-the-shelf form the cameras are limited to a maximum exposure of 1/5s by an electronic shutter and are therefore of little use for imaging deep sky objects. However, with minor modifications to the circuit board it is possible to disable this shutter and control the clock pulses which are used to readout the CCD using the parallel port of a PC. The ultimate length of the exposure is then limited to the fact that the cameras are un-cooled and thermal noise begins to dominate. This is particularly evident in a weak infra-red emission from an on-chip charge amplifier which produces a strong emission for exposures greater than about 20s. Furthermore, hot pixels also become significant and require the use of dark frames. Finally, the cameras are only 8-bit monochrome which results in the digitisation from black-white in 256 levels of greyscale. When imaging deep sky objects, where significant dynamic contrast can be present, this can become somewhat of a limitation.
This talk will explore the modifications which need to be performed on a 1004 x CCTV camera in order to make it suitable for astronomical imaging. The topics of basic long exposure modification, amp off modification and peltier cooling will all be discussed. Furthermore, the ability to do mosaic and narrowband imaging will also be considered. It is also hoped that a couple of modified cameras (a Philips SPC900NC and 1004X) can be brought along and demonstrated.
Dr Hammond obtained his PhD in Experimental Gravitational Physics from the University of Birmingham in 1999. His thesis concerned the development of a low temperature superconducting torsion balance
to perform precision tests of gravity and quantum field theory. Giles then moved to JILA, University of Colorado , for a couple of years where he was part of the team developing active/passive seismic isolation systems for the LIGO gravitational wave detectors. In 2001, Giles returned to Birmingham to take up a postdoctoral research position. During this time, together with a couple of colleagues, he was able to place new limits on interactions coupling spin to gravity and also perform preliminary measurements of the casimir force at 4K. Both of these are firsts for the field. In late 2007 Giles moved to the University of Glasgow and currently holds an RCUK academic fellowship in the Institute for Gravitational Research. His day to day work concerns the development of techniques to measure surface charge on optics as well as produce fused silica suspension elements for the next generation of gravitational wave detectors.
Giles is a keen amateur astronomer and when possible does imaging from the back garden with modified cameras and a recently procured 16-bit imaging camera.
The Observing Group wil meet at 6:45pm prior to the main meeting.