Auto Focus Tutorial
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How it Works

Refer to the Conceptual Diagram below.  The Tele Vue Focusmate equipped Tele Vue telescope is outfitted with the (optional) Tele Vue Digital Indicator (focus measuring device) and Tele Vue Focusmate Driver (focus motor). These both connect to the Focusmaster (computer control box). The Focusmaster interfaces this Tele Vue hardware to your computer. A camera attached to the telescope is connected to the computer.

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Starting with the image focused by the operator, the third-party software (MaxIM DL, Astroart, etc.) requests an initial image from the camera (purple arrows). Through the Focusmaster, the software instructs the Focusmate Driver to turn the Focusmate fine-focus accessory (red arrows) to another focus position (position data through yellow arrow) and another image is taken. Comparison of the two images' full-width half-maximum (amount of energy concentrated in the center of stellar images) leads the camera to decide which direction to move the focuser and take more images. The goal of this iterative process of fine-focusing and imaging is to take images on either side of focus and mathematically determine the central position of best focus. Because the indicator is measuring the actual position of the draw tube, the autofocusing routine can then drive the focuser to the exact calculated point of best focus.


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