ASTRONOMICAL IMAGES WITH A DIGITAL CAMERA
By Shevill Mathers

At the July 2001 General Meeting of the AST, one of the cameras that I briefly demonstrated was a recently purchased Nikon Coolpix 995 digital camera. For some time I have been investigating digital cameras for another scientific purpose, a “Whole Sky” camera for recording daytime cloud cover and cloud types. The Nikon was one camera evaluated because of its 183 degree fisheye add on lens. Three other lenses are also available. An electronic cable release and timed interval recording was another important feature.

The Nikon Coolpix is a 3.34-mega pixel digital camera has a non-removable 4 x zoom lens with the facility to attach additional lenses. There are various image quality settings; Basic, Normal, Fine and Hi, which is uncompressed TIFF format of 9 MB file size with a maximum resolution of 2048 x 1536. Not all digital cameras have this feature, which is very important if one is looking for maximum quality pictures. Many cameras only use JPEG format, which is a lossy compression
format so image detail is lost. This Nikon digital camera is not in the professional range of 35mm digital cameras, which cost considerably more, however, the image quality gap between nonprofessional and professional quality is getting narrower. The manual that comes with the camera is about 10mm thick and is pretty intensive reading. The only things this camera cannot do is put the kettle on and make a cup of tea!

As a professional photographer with lots of expensive film cameras of various formats including a lot of Nikon equipment, I knew that the Coolpix 995 had to be pretty impressive. The list of accessories for the Coolpix 995 is quite extensive and also makes use of an existing Nikon flash units for multiple flash uses. An important accessory is a remote cable, which combines several functions. It is an electronic cable release, zoom control, and a timer for interval photography,
which allows for a programmed series of photographs from 2 minutes up to 24 hours. When set, the camera switches itself on takes the picture and switches off until the next shot. Perfect for time delay nature photography and astronomical applications!

Another very useful feature in manual mode is the ‘B’ setting, which allows exposures of up to one-minute duration. Another fantastic feature of this camera is the extensive amount of information saved with each picture. A sequential number, date, time, shutter speed, aperture, focal length, lens used, file size and a host of other information. It means being able to shoot off photo’s without worrying about remembering the where and when details. This information stays with the picture at all times – magic!

To use this camera on the Takahashi scope I decided to machine a matching thread on a Tele Vue 15mm Plossl eyepiece, which I then screwed into the front of the camera lens. The whole sky shots were with the standard and wide-angle lenses, including some shot of a large Moon halo taken with the fisheye lens.

I was not disappointed with my first shots with this camera, which were of a longhaired cat at the ‘fine’ quality setting. The fine hairs and whiskers are quite a good test of detail and an A4 colour print with my Epson Photo printer was impressive to say the least.

The first astro photographs with the Nikon Coolpix are lunar shots for my “Moonlighting” series in SKY & SPACE magazine. Also the recent pre-dawn line up of the Moon, Jupiter & Venus. Large Sun Spot groups and some one minute time exposures of constellations, Orion and the Southern Cross. (Not shown)

S.M.

The Moon‘s southern region is a mass of craters of all types and ages.
A favourite of many lunar observers is the giant crater Clavius, with its crescent shaped line of craters across its floor.

The magnificent crater Copernicus dominates the moon’s central landscape, with it’s central mountain peaks and terraced walls, a must for all lunar observers.

All images © Shevill Mathers - reproduction without permission prohibited