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Download Telescope Tear-Down
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Telescope Tear-Down Anatomy of a 114mm f/8 Newtonian Reflector The Newtonian Telescope The Mirror Cell Lock Adjust COLLIMATION • Aligning the optical axis • Centreing the light cone in the secondary mirror and eyepiece The Optical Axis • • • • • • The direction the telescope is pointing All light from the focal point reflects parallel to optical axis Line from centre to focal point Axis intersects mirror at 90 degrees Focal point halfway between centre and mirror See reflection of eye where axis intersects mirror Adjusting the Primary Mirror • Still see reflection of eye where axis intersects mirror • For parabolic mirrors the optical axis should intersect the mirror in the CENTRE. • Align axis with tube to avoid tube blocking light. Quick Primary Collimation The view down the tube • When reflection lines up with secondary we see the optical axis • Adjust primary to centre optical axis • Primary now roughly aligned with tube • Secondary reflection in centre of primary mirror • Reflection of camera lens (eye) in centre of mirror Secondary Mirror Alignment 1 - Secondary mirror position • Position mirror under centre of focuser tube Secondary Mirror Alignment 2 - Aim the secondary mirror • Centre reflection of primary • Should see whole mirror - don’t cut off light! Final Primary Collimation • Reflection of eye is on the optical axis • Move eye to centre of primary mirror How close? • Only eye reflection & centre matters • F/8 => 11mm radius • F/6 => 5 mm radius • F/5 => 2.7mm radius • Radius = Focal ratio3 x 0.022 mm
