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  1. C

    extension tube lenght alters focal lenght?

    Many thanks Daniel! Not sure I got any wiser, though..haha, but I'll have to let it sink in a bit I guess :-) " Some testing with a ruler and some simple math might give the answer. " Do you have some web page in mind or what to search for, so I can learn how to do that (calculate)? many...
  2. C

    extension tube lenght alters focal lenght?

    at the moment I have approximatedly 10-11 cm extension tube lenght (80mm and pushed out a bit, as well as the camera mount adapter out a bit. one of the photos below was taken at 300mm (zuiko 75-300) the other with the 600mm celestron 80ED, and sitting at the same spot. Sensor plane difference...
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