OPTICS QUESTION

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  • Last Post 09 September 2016
joeb33050 posted this 08 September 2016

Does anyone KNOW if changing focus on a Weaver T36 changes POI? Thanks; joe b.

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RicinYakima posted this 08 September 2016

Joe,

I KNOW that it CAN depending upon tolerances of the lens holder! The objective lens that adjusts the parallax (focus for distance) can be sensitive. The ocular lens that adjusts the focus for the cross hairs not as much, unless the thread tolerances are really loose, or the lock ring is not flat.

Ric

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Ken Campbell Iowa posted this 08 September 2016

the rear lens unit ...eyepiece... will not change impact ... it only focuses on the already-aligned image of the front lens and crosshair..... as you turn the eyepiece the image of the bullseye/crosshair may go around and around but the crosshair will stay on the bullseye .

moving the carriages for either the front assembly or the crosshair might cause some movement .

remember that impact can also change for many devious reasons :: where your thumb is at on your stock
where your elbow is on the bench muscle tension in your sore knee joint fly walking on your neck 2 degree change in air temperature

did you know that 1 minute of angle is only 1 part in 21600 of a circle ?? what is all this fuss about 1/4 of 1 minute of angle ??

plinking power matters ...

ken

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RicinYakima posted this 09 September 2016

My only disagreement with Ken is that the human eye does not see the crosshairs equally crisp and on target as the rear lens rests in different positions. Us old folks focus on the sharp image more than the fuzzy one. I have used too many old Weaver scopes from the 1960's that had threading so bad the crosshairs would move, to my eyes, with a 1/4 turn of the lens. Ric

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