In the picture above, the eyepiece is a Meade 28-mm Plössl and the T-thread extender is largely to
accommodate the eyepiece. (It is shown unscrewed to reveal the eyepiece.) I was able to alter the distance between the eyepiece and the camera by
using different M42-extension rings. The one shown in the picture is the longest one; with no
extension ring there the distance from the eyepiece to the camera was 44 mm.
(Note: Meade make three camera adaptors of which I have two. One holds an eyepiece and the other doesn't.
The T-thread extender came from the second one (and I have more that came with the focal reducer).
Meade's third adaptor allows adjustment of
the distance of the camera from the eyepiece directly. Unfortunately I don't have one.)
The magnification produced by this method,
as with a barlow or any other lens system, depends on how far the camera is
from the eyepiece. I took some pictures of Saturn using the 26mm eyepiece with different
distances between the back of the eyepiece and the camera. The results are shown below.
Distance (mm)
Magnification
(relative to prime focus)Saturn
Prime Focus
1.0
44
0.9
64
1.6
74
2.8
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