My initial lunar photographs through my telescope were obtained by holding the digital camera close to the eyepiece. One of the difficulties of that method was maintaining the camera lens in line with the optical axis of the eyepiece and close enough to avoid vignetting. An existing camera adapter I had previously used with my SLR film camera seemed to offer some benefits in lining up the digicam and eyepiece.
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The camera adapter can be seen in the adjacent image. It comprises a 1.25" barrel section that fits into the eyepiece holder of the telescope. The larger diameter flange of this is threaded for a camera T-ring adapter, to allow an SLR film camera to be used at the prime focus of a telescope. Here, however, the flange is screwed into a larger diameter cylindrical section into which can be placed an eyepiece, secured by a clamping screw. The opposite end of this cylindrical scetion is likewise threaded for a T-ring adapter, so that - with an eyepiece inserted - a camera can be used for eyepiece projection photography at the telescope. |
Used with a digicam, however, the function of the adapter is just to help locate the camera lens at the eyepiece. The Fujifilm Finepix A405 camera has a lens assembly with an outer diameter of approximately 1.25". The cemera adapter eyepiece section T-ring aperture is several millimetres wider in diameter. A plastic plumbing washer which fitted into this larger diameter and which had an inner diameter of 1.25" was thus used to assist in locating the camera lens. This washer is also shown in the image, together with a 6.5 mm Plössl eyepiece.
| The eyepiece was secured within the adapter with a few millimetres recess from the T-ring adapter aperture. The washer was then seated in this recess, as shown in the adjacent image. With the adapter inserted into the telescope eyepiece holder, this arrangement allowed the eyepiece to be used by eye prior to photography to confirm focus and telescope orientation. |  |
Having set up the telescope with the adapter, configured with the 6.5 mm eyepiece, the telescope was focussed (using the Hartmann mask) on the Moon and the digital camera was placed so that its lens slotted into the washer. In this was various photographs were taken, with the various zoom and resolution settings.
| The best example is shown opposite. This was
obtained with the above configuration at approximately 22:12 UT on 29
February 2004, using 1 Mpixel resolution. The image has been reduced to
40 per cent in size, converted to grey scale, rotated by 30 degrees and
cropped. The Moon was about 9 days, 13 hours old when the image was
obtained, and it shows craters Maginus, Tycho, Gauricus and Pitatus (top
left to bottom right). The camera adaptor and washer arrangement did allow the camera to be brought close to the eyepiece and accurately centred on its optical axis. However, with manual operation of the camera shutter it was very easy to make the telescope vibrate. Thus, elimination of vinetting has been at the expense of increased likelihood of telescope vibration, which diminishes the value of this approach. |
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Last updated: 31 May 2004