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ETX-125 zero image shift rear port focus mechanism 12-27-04

Focuser makes use of a fine thread lead screw to adjust the distance between the CCD camera and the rear port.
Not only does this improve the ability to focus properly, but it allows the CCD camera and the
eyepiece to focus at precisely the same spot when using the '-normal-' ETX-125 focus knob.
Remote controlled focus motor not installed when these photos were taken.

Take note of the calibrated scales in the lower right photo. One revolution of the knob moves the camera 1 cm and is set at 4.3225 cm in the photo! It's possible to adjust the focus one way or the other and then return to precisely where the focus was before it was moved. Why don't all telescopes have a calibrated focuser? I'm not sure what this item was used for originally. It was bought at a hamfest fleamarket for $5. What looks like an eyepiece holder just below the lead screw is NOT used in this application as it moves about the wrong axis.


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