These 4 images illustrate the
principle of eyepiece projection astrophotography. They were taken with a C8, 2 eyepieces
of 25mm and 10mm, an adjustable telextender from Meade, and a Canon A-1 fitted with a T-ring.
The telextender holds one of the eyepieces in such a way as to place it between the telescope
and the camera. It's adjustable in that it consists of two telescoping tubes, one inside the
other. This allows the operator to change the distance from the back of the telescope to the
film plane of the camera, thus changing the effective magnification of the object observed in
the telescope. The longer this distance, the greater the magnification. The top two images
(Crater 1 and Crater 2) show the range of magnification from minimum to maximum with the
25mm eyepiece installed in the telextender. The bottom two (Crater 3 and Crater 4) show the
range with the 10mm installed. In case you haven't noticed, all 4 shots are of the same pair
of craters. The image got rotated when I changed eyepieces and forgot to realign the camera
in the same orientation as the original 2 images. Oops. The pictures below show the
arrangement a little better.
Figure 1 shows the actual pieces of this puzzle. The camera body on the left, with the
cable release attached, the eyepiece drawn out of the telextender so you can see it, then the
T-ring attached to the telextender tubes. The two screws on the left section allow the tube to
be drawn out and secured, the screw on the right section secures the eyepiece inside the
telextender.
Figure 2 shows the whole thing attached to the back of the C8. (I suppose I should have
aligned the components in figure one in the opposite direction, to match the orientation of
figure 2, but I didn't think of it til just now. Another oops.)
Figure 3 shows a nice drawing of the arrangement.
Page URL: http:/www.stonehavenobservatory.com/Craters.html
Copyright 1999, Steve Dodder
Webmaster
: Steve Dodder
Revised: 8/26/10
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