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When it comes to celestial photography there is a massive range of possibilities for equipment and a corresponding range of results which can be achieved. An 18 inch reflector telescope with high quality optics and a high resolution camera might produce breathtaking "hubble quality" images, with which a quick snap at the moon with zoom compact camera cannot possibly compare. But perhaps every photographer who buys a new long-focus lens, will test it out by photographing the moon. The author is in this latter category and on this page are compared some results of three camera-lens configurations which he has tried out in this way.There are many lunar pictures available, but it is hoped that this page will give the reader some idea what to expect from equipment certainly at the economy end of the market.
The most obvious start in an attempt to photograph the moon is to use a long-focus lens and in this example, a 500mm Soligor mirror lens was chosen as an inexpensive option. This lens, fitted to a Canon 550D Digital Single Lens Reflex camera is shown above, left. It is a single aperture lens with manual focusing and is attached to the camera via a T-mount/Canon bayonet converting ring.
Even at 500mm focal length, camera shake is a problem when hand-held, so the use of a tripod is preferable, but since the moon is usually a very bright object, fast shutter speeds can be employed to obviate the worst effects of camera shake.
The results are shown in the image above right. The smaller of these lunar images shows the degree to which the moon fills the field of the camera using the 500mm lens, and this reveals that 500mm focal length is insufficient to exploit the resolution of the camera for lunar photography. The larger lunar image was generated by digital enlargement and shows relatively poor degrees of detail in the lunar surface.
An attempt was made to improve on the performance of the 500mm lens by the use of a Viking AV50 Terestrial telescope attached to a Nikon Coolpix 4500 camera. Both of these items are now obsolete but modern equivalents are available. The AV50 telescope was estimated as equivalent to perhaps an 800mm lens on an SLR camera. The Nikon Coolpix 4500 was a popular camera for interfacing with telescopes and microscopes because focussing and zooming functions did not move the front lens which could thus be attached to other optical components via its 22mm outer thread. Brunel Microscopes Ltd supplied a machined aluminium adapter to allow the camera to be attached to an eyepiece.
The photgraph above left shows the image which could be obtained with this set up. The optical resolution of the telescope was not matched by the digital resolution of the camera but the result was decidedly better than that obtained from the 500 mm Soligor lens.
Much more light was available from the uneclipsed moon and so detail is greater and exposures of about 1/30th second were employed. The required exposure increased as the eclipse developed until about 12 seconds were required at the full eclipse. Since the moon moves significantly in this interval, resolution of details on the lunar surface was reduced. The blood-red colour of the eclipsed moon, however, is very well represented.
The third set up for lunar photography was a Canon 550D Digital SLR furnished with an Opteka 800- 1300mm zoom lens and a x2 convertor. This was a relatively heavy and bulky arrangement and was originally set up on a photographic tripod as shown above, left. This simple arrangement suffered from several disadvantages: (a) Even though a reasonably stout tripod was used, the assembly was too heavy for it: joints in the mounting were not rigid enough to support the lens and camera with sufficient mechanical stability. (b) Because the assembly was attached to the tripod only at one point, the weight of the camera had to be supported by the lens mount, which was unequal to the task. (c) The positioning of the camera lens via the pan and tilt mounting on the tripod, was far too imprecise to track the moon at that magnification. Small adjustments, necessary since the moon traverses its orbit significantly during the set-up time, could not easily be made. For this reason, the tripod was abandoned and an equatorial telescope mount was substituted. The Camera and lens were mounted on a T-section aluminium bar which was bolted to the telescope mount as shown in the figures below:
This resulted in a much more mechanically stable arrangement and one which was much more easily adjusted to maintain the moon in the field of view of the camera. The remaining difficulty was that of precise focussing and a fine focussing control would be an asset, particularly at high magnifications.
In the photograph below the two right-hand images were of a gibbous moon and a new moon both captured with the apparatus described above.