Quote:
Originally Posted by bmitchell82
I have heard of this, but there has to be some way of "knowing" where it will come to focus in the draw tube. i would have thought that there would be something that i can do :S becase in any case i would prefer not to start hacking and slashing at my ota  |
Ah, yes, there is.
The procedure is to use a frosted glass surface against the end of the focus tube to determine when the focal point is level with the end of the tube. Then measure the distance that the tube is out of the focusser.
Next, put your camera on the scope and adjust until the camera is in focus and again measure how far the tube protrudes from the focusser. The difference will tell you where the focal plane of the camera is relative to the end of the focus tube.
Now you repeat the frosted glass part of the experiement again on the new scope, and make sure you have enough adjustment before full in/out focus.
You can use a piece of 3M Magic tape on a glass slide for the frosted surface, or possibly even grease proof paper if you can hold it flat and taut across the focus tube.
Al.