Alignment between clip on and objective

[mark82]

So I dont know very much about current NV options. Looking into "clip on" which I assume means a device that is separate from and mounts in front of regular scope. Similar to PVS30.
My concern is the required alignment between the scope and the NV device. I have a 50mm objective that is only about 0.150 above the rail (to bottom of objective). Pics of PVS30 with mount look like it will not sit very close to top of rail, so the scope will be a good bit lower than the PVS. Is this a problem and how do you handle misalignment?

Thanks

 

[RTH1800]

Alignment is calculated center to center.

 

[B21TLB]

So I dont know very much about current NV options. Looking into "clip on" which I assume means a device that is separate from and mounts in front of regular scope. Similar to PVS30.
My concern is the required alignment between the scope and the NV device. I have a 50mm objective that is only about 0.150 above the rail (to bottom of objective). Pics of PVS30 with mount look like it will not sit very close to top of rail, so the scope will be a good bit lower than the PVS. Is this a problem and how do you handle misalignment?

Thanks

The eyepiece center on most Mil-spec clip ons will be 1.535 in from top of rail. The further from the optic center line your day optic is the greater the potential shift in zero is, but its usually not much. It is much more important that the lens are perpendicular, if they aren't you will definitely have issues at some point. That point is dependent on the optical design of the clip on's eyepiece.

 

[nutation]

To elaborate on @B21TLB 's post, there are several posts and threads which discuss both clip-on vertical and angular offset.

Angular misalignment tolerance
Angular misalignment and clip-on design
CNVD-LR angular offset
PVS-27 angular offset
Clip-ons and cant
CNVD-LR and vertical offset

The upshot is that clip-ons with shorter tail sections (PVS-27, PVS-30) are more tolerant to offset than those with longer tails (PVS-24LR), and that angular offset is the more important consideration. I can confirm that even a 40 MOA cant does not induce much noticeable shift in the PVS-27, which has a very short tail section.

 

[nutation]

A bit more about height offset from Spuhr.