This week was another joint Zoom talk hosted by Beeslack Penicuik Camera Club. Paul Money, an astronomer and ‘Reviews’ editor of the BBC ‘Sky at Night’ magazine, connected from Lincolnshire to give us a guide to astrophotography. Paul has written a book on astrophotography called “Nightscenes: Guide to Simple Astrophotography” and mentioned that a new version of that book is about to be published.

Paul began by describing his early forays into astrophotography, using a Zenit film camera and high ISO slide film. Those were difficult days for astrophotography because the relatively low ISOs meant you needed long exposures, and you couldn’t see what you were getting until the film was developed. Paul was enthused by the latest developments in digital photography. His latest Canon camera can go up to 120000 ISO, and even modern mobile phones can now capture hand-held images of the night sky! Canon and Nikon cameras seem to be equally good at capturing good images of the night sky. We were given the following hints and tips for good astrophotography:

• Turn off the noise reduction in your camera settings. Faint stars look like noise and will be removed.
• Set your camera to manual exposure and manual focus. Most night shots are too dark for your camera’s autofocus to work properly. You can focus on a bright street light at least a mile away or use the “live view” option on your camera to adjust the focus to make the stars look as small as possible.
• Most exposures will need a high ISO setting, but Paul recommends going no higher than ISO 1600 to get the best quality. Shots of the Moon or bright planets can be done at lower ISO settings.
• Use a wide aperture, ideally a stop down from the widest setting of your lens. Paul tends to use f/5 but recommends stopping down to f/11 for scenes which include the full Moon or bright lights.
• Use a decent tripod so you can take long exposures without camera shake. You can fit the tripod with a ball and socket bracket that allows you to point the camera upwards at any angle.
• Also use a remote shutter release; preferably one that can make a timed exposure or take several exposures at regular intervals.
• Don’t use a filter. You need to get as much light into your camera as possible through as few glass surfaces as possible.
• Use a red light to help you see without spoiling your night vision. You can buy a special red torch or just cover an ordinary torch with a red wrapper.

Paul then gave us a quick introduction to the night sky. The stars rise in the east and set in the west and appear to rotate around the north celestial pole. If you point a camera north and take a long exposure you will see star trails revolving around the pole. The stars tend to move more slowly in the sky around this point, so you can get away with longer exposures before they start to trail. If you point your camera away from the pole the stars will move across the sky more quickly and you’ll need a shorter exposure. The exposure also depends on the kind of lens you are using, with telephoto lenses requiring the shortest exposure. Paul gave us the following guide to maximum exposure time before the stars start to trail:

• Wide angle lens (18mm): Near the pole (60 seconds), Away from the pole (40 seconds)
• Standard lens (50mm): Near the pole (30 seconds), Away from the pole (20 seconds)
• Telephoto lens (135-300mm): Near the pole (20 seconds), Away from the pole (10 seconds)
• Super telephoto (500mm): Near the pole (2 seconds), Away from the pole (1 second)

Paul took us on a quick-fire, enthusiastic and fascinating tour of various types of astrophotography, ranging from wide-angle shots of the constellations, star trails with foreground objects, telephoto views of the planets, a lunar eclipse, Earthshine on the Moon, noctilucent clouds and shots of the aurora borealis. Paul mentioned that, although most photographers like Adobe Photoshop, he prefers PaintShop Pro. He also recommended StarStax software for combining multiple images of the night sky.

If you would like more information here are some of our previous talks on astrophotography:

Ford Renton: Practical Astro-photography

Andy Bennetts: Astrophotography & Action Photography

Next week we have a Digital Photo Feedback session. This session replaces our old “Photo Advice Night”, which was based on prints. Please bring along up to 6 digital images (or email them to me) to get feedback and advice from other members. See you on Thursday.

Steven