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A barlow makes the light cone less steep and pushes the focal point out past the eyepiece. To bring the focal point back to the eyepiece the main telescope mirror needs to be moved toward the rear cell by turning the focuser clockwise. It will take quite a few turns of the focuser to achieve focus; if you're going in the right direction the doughnut will be getting smaller.
A reducer has the opposite effect and the focuser has to be turned anticlockwise a lot, pushing the main mirror forward in the tube.
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