This week we had a visit from Ford Renton of Galashiels Camera Club. A few years ago a Ford visited the Royal Observatory in Edinburgh for an introductory workshop in astrophotography organised by Eric Titley. Ford was inspired by that workshop, and this evening he took us on his journey from the practice shots he made after the workshop to his more recent spectacular starscapes and deep sky images. Ford’s photographs ranged from simple, single long exposures taken at night to multi-exposure stacked star images. Ford had this basic advice for all photographs of the night sky:
- Mount your camera on a sturdy tripod and turn off image stabilisation.
- Set your camera to manual mode (M).
- Set your camera or lens to manual focus and focus on a bright but distant object (such as a street lamp or tower several miles away). If your focus ring is likely to drift when you move the camera, fix it with some electrical tape.
- Go into your camera settings and turn off long exposure noise reduction, otherwise this will remove the stars.
- You will get the best results with a simple, prime lens.
For the simple starscapes, Ford recommended a wide angle lens, set to a wide aperture (f4 to f2.8), a high ISO setting (3200) and an exposure time of about 15-20 seconds. Longer lenses need a shorter exposure time (e.g. less than 1s for a 400mm lens) to prevent the stars trailing. To make star trails deliberately, you would use a lower ISO setting and a longer exposure. An exposure time of 90 minutes can be created by taking 60 successive 90 second exposures, stacking them in Photoshop and using the “lighten” blend more to merge them. Alternatively, a software package called StarStax can also be used. A “median” stacking technique can be used to reduce the background noise in the high ISO images.
For the deep sky images, Ford recommended investing in a star tracker, such as the iOptron SkyTracker Pro Camera Mount with Polar Scope. This device allows the camera to track the stars and make long exposures without trailing them. The best results can be obtained by stacking several images to lengthen the exposure time and reduce the noise. Ford uses a wide variety of software packages, such as RegiStax or Deep Sky Stacker. Ford ended his talk with a spectacular shot of the Horse Head Nebula, obtained without the aid of a telescope.
Ford has also compiled a comprehensive guide to astrophotography, covering the many other techniques he mentioned which I haven’t mentioned. Click on the link below for a copy of the guide: