Flamsteed AS Ian King Astrophotography

Flamsteed Astronomy Society

Astrophotography & wide-field CCD imaging

— Ian King November 7, 2005

Ian says he takes ‘pretty pictures with no scientific value’. Hmmm. Ian’s astro-photography images are stunning. If his pretty pictures don’t take your breath away then nothing about the night sky ever will. Ian gave us a rundown of his efforts starting with a tour of his annual trips to La Palma in the Canaries. For some five years Ian and party have been decamping to Roque de los Muchachos and working right beside the Isaac Newton Group of telescopes on the mountain top. The view is breathtaking. 70 miles away, Tenerife stands clear floating in the sea of cloud tops. The telescope domes provide dramatic props for Ian’s scenery shots and for his night-time star trails. The clarity of the air and the sunset colours are captivating. But none of it comes easily. The excess baggage bill alone must be considerable! And the weather isn’t all balmy breezes either. There’s a very real risk of being marooned on the mountain by snow storms which can turn the mountain roads into icy death traps.

Ian gave us a rundown on the stages of astrophotography starting with film and using conventional cameras with 50mm and upwards lenses. Ian can get spectacular results, but the long continuous exposure times mean this is a mainly job for La Palma. The light pollution in the UK rules out many of the superb shots possible in the Canaries and one slip can ruin a long exposure. The image post-processing needed with complex film shots is daunting.

Enter CCD technology. Digital CCD chips have transformed astrophotography just as they have our family snaps. It’s now possible to build up very long total exposure times in many short bursts — much less chance of ruining a continuous long exposure. And CCDs capture every photon, unlike film which suffers from ‘reciprocity failure’ — its sensitivity falls off sharply during long exposures. Image processing software has mushroomed. Not that it’s easy to produce images like Ian’s. The skill and time invested in his pictures is awesome.

Ian shared a host of images made with different kinds of technology: CCDs and filters, and took us into some of the details of monochrome v. colour CCDs. Narrow-band filters have opened up a whole new range of options. Using filters like Oxygen O-III and Hydrogen H-alpha brilliant new views of the sky can be made. Narrow-band filters used with suitable CCD devices are also impervious to light pollution.

But let the images speak for themselves …

MRD