Rifle Scopes About WHERE in the scope tube are FFP and SFP?

[Grump]

It's been forever since I've seen a diagram of the optical path in a straight scope (or anything else other than a Schmidt-Cassegrain).

In the interests in measuring to the inch my distance from scope to the calibration target (optical box test), can anyone point me to how to find, or where they usually are?

I'm thinking that some general ratio of X% of the distance from ocular lens to the objective, or something like that.

Thanks!

 

[dcjs]

Re: About WHERE in the scope tube are FFP and SFP?

Grump,

as a general rule, you will find the FFP reticle a short distance in front of the adjustment turrets, and a SFP reticle where the vario ring sits (~2" in front of the ocular lens). Of course this is a rough estimate, but it should get you to within about an inch of where you want to be at. Not sure I understand what you are going to use this information for regarding a box test though.

 

[doc76251]

Re: About WHERE in the scope tube are FFP and SFP?

Grump,

When I teach my optical calibration class I use 1 1/2 - 2" in front of the center of the turret for FFP scopes and just forward of the power ring for SFP scopes. That covers most scope mfg's to w/i 1" which is w/i the amount of error in the human eyeball when it comes to measuring on the chart.

Cheers,

Doc