Visual indicators for eliminating scope cant

[nced]

Sorry, nced, but optical centering using a mirror is not the only thing you can do with one.... However, starting with an optically centered scope is a good idea before you do the steps outlined in Jason's post (and my modified version)…. The key to using a mirror to avoid cant errors is this part of that process....

set up a mirror at 5 yards, set your scope's parallax to 10 yards, and look through the scope at your reflection in the mirror.

Bob

Interesting, never tried that. I always simply set the ao to infinity, the scope power to "minimum", placed the "scope bell" directly on a well lit bathroom mirror, then aligned the reticle. Gonna try your "5 yards, set your scope's parallax to 10 yards, and look through the scope at your reflection in the mirror"  method to see how it works. One of the issues with placing the "front scope bell" on the mirror is that the reflection of the reticle is dependent on how perpendicular the scope is to the mirror and scopes can have a front objective that isn't perpendicular to the scope body.

I remember years ago when the optical centering of a particular 4-12x40 Hawke Airmax didn't match even remotely (LOL....not even in the same quadrant) close when centering the reticle using the mirror method, the Hawke recommended (at that time) "count clicks divide by two" or the "spin in vees" method. It's also interesting to me that this particular scope would shift the poi laterally simply by focusing and shooting a group at 18 yards and then focusing and shooting at 10 yards.......

It's also interesting that these two groups shot at 18 yards and again at 10 yards should have been "stacked vertically" by about 1/2" instead of aligned horizontally. Anywhoo.......all the scopes I've bought since (44mm or 50mm objective lenses) had the reticle reflection aligned within a couple clicks straight from the box.

[rsterne]

The mirror at 5 yards is not for optically centering the scope, of course.... You view the reflection of the scope and gun in the mirror, and twist the scope in the rings until the vertical crosshair bisects both the muzzle and the objective bell of the scope at the same time.... That insures that the crosshair is aligned with the bore....

Yes, when using a mirror to find the optical center of the scope, the bell has to be perfectly square to the scope axis.... but that is another subject.... My guess is that the gun that shot that target had the scope offset from the bore.... I had a Hatsan like that.... Using the mirror trick to get the crosshair lined up with the bore cured it completely....

Bob

[nced]

The mirror at 5 yards is not for optically centering the scope, of course.... You view the reflection of the scope and gun in the mirror, and twist the scope in the rings until the vertical crosshair bisects both the muzzle and the objective bell of the scope at the same time.... That insures that the crosshair is aligned with the bore....

Yes, when using a mirror to find the optical center of the scope, the bell has to be perfectly square to the scope axis.... but that is another subject.... My guess is that the gun that shot that target had the scope offset from the bore.... I had a Hatsan like that.... Using the mirror trick to get the crosshair lined up with the bore cured it completely....

Bob

"had the scope offset from the bore"
Nope, the Aeon and Vortex Diamondback I had mounted on the same .177 R9 didn't do a "focus related poi offset" like the Hawke Airmax with a 40mm AO. The position of the groups, regardless of the "bore alignment"  should have been stacked vertically after focusing on the same bull and shooting due to the pellet rise from the bore to the line of sight.

Here is a target I shot from 10 yards to 50 yards checking the trajectory of a tune. My "far zero" was 30 yards which gave me a 17 yard "near zero" and the group on the 10 yard bull was 3/8" lower than the group at 17 yards............

The gun is the same that shot the above groups  two groups using the AirMax. I don't remember which scope I was using but in 2009 I think it was a 4-12x40 vortex diamondback.

[nervoustrigger]

Ed, regarding the POI shift with the Hawke Airmax, just a reminder we dispelled that diagnosis here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=116903.msg1124226#msg1124226

But I'm confused...the pictures from that thread are now gone but the one in this thread doesn't seem to be the same.

[nced]

Ed, regarding the POI shift with the Hawke Airmax, just a reminder we dispelled that diagnosis here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=116903.msg1124226#msg1124226

But I'm confused...the pictures from that thread are now gone but the one in this thread doesn't seem to be the same.

I lost a lot of pics when PhotoBucket decided to hold my pics "hostage" and I didn't pony up for the extra $$$$$ so some were "re-shot for posterity". LOL.....I've even been saving my "photo hosting folders"  to my hard drive, then burning the folders periodically to DVDs just in case I lose them again due to "photo hosting site shenanigans". 

LOL....... I'm confused because I replied in that thread................
"To clarify I just took my .177 R9 with 30mm tube Optisan Viper scope mounted in a high BKL mount, and  after deliberately turning the windage turret 3 turns out of zero I shot two 5 shot groups (one at 18 yards and one at 10 yards).
This scanned target and shows the two groups separated vertically by about 3/4" after shooting at the same bull, but not aligned horizontally like I got with the Hawke scope."

Seems to me that the above reply verifies that when focusing and aiming at the same bull from 10 yards and then 18 yards I got "stacked groups" instead of the "horizontal groups" I got with the 40mm AO AirMax. 

[rsterne]

Then I guess the Airmax had a POI shift as you rotated the AO.... an offset, or asymmetrical objective lense?....

Bob

[starlingassassin]

just an FYI

the white caps that come on the little test tubes tubes in an h&n pellet sampler pack,

fit nice and snug on standard diameter crosman barrels (1322/disco/maximus/etc...)

and are easy to see when using the mirror method.


if you're aligning your scope indoors or a less than well lit environment,
hit the end of the cap with a bright color spraypaint.


also,as an added bonus,
they are great for storing barrels so the crowns are protected 
add another one on the other end and it also protects the breech end and covers the transfer port hole.


i love when i find an item designed for one thing but can be perfectly used for another