T
tommyo
Guest
If it is important, how do you get it back to center? Run it all the way to one extreme and then go back and count clicks, then set in the middle?
That will get you close.
But to do it correctly, I set mine in a set of V Blocks and turn the scope CW or CCW and watch what happened to the cross-hairs. If they are off I turn the knobs to bring the cross-hair a few clicks and see where they are when I return the scope to it natural upright position. It's a trial and error process, and quicker than sending the scope back to the manufacture to have it re centered. When optically centered, you will have your brightess sight picture and less glare.
But to do it correctly, I set mine in a set of V Blocks and turn the scope CW or CCW and watch what happened to the cross-hairs. If they are off I turn the knobs to bring the cross-hair a few clicks and see where they are when I return the scope to it natural upright position. It's a trial and error process, and quicker than sending the scope back to the manufacture to have it re centered. When optically centered, you will have your brightess sight picture and less glare.
Yes but, depending on how the barrel was installed you might not be able to zero your rifle and keep the reticle in the center of the scope. If this is a factory rifle, epically a Remington 700, the barrel may be looking off slightly to one side or another. If it's looking up or down this will be a non-issue. Either way, accuracy of the rifle will not be affected by reticle position in the scope.
C
Cheechako
Guest
tommyo
Center the reticle (crosshair) just as Fred recommended. You can make a V block out of a piece of 2x4 and some heavy cardboard. If you cannot figure out how to do it I can post a picture of mine.
If you use a base and rings such as Redfield, Leupold, Burris, you can make horizontal adjustments to correct any offset resulting from out-of-line bases. The dovetail receivers such as Stolle are usually very close to center.
Is it important? Being off a little probably doesn't make any difference and it should not affect accuracy. Read the specs on your particular scope. I don't think I would want to use up more than 1/4 of the adjustment range just to get the reticle centered.
JMHO
Ray
Center the reticle (crosshair) just as Fred recommended. You can make a V block out of a piece of 2x4 and some heavy cardboard. If you cannot figure out how to do it I can post a picture of mine.
If you use a base and rings such as Redfield, Leupold, Burris, you can make horizontal adjustments to correct any offset resulting from out-of-line bases. The dovetail receivers such as Stolle are usually very close to center.
Is it important? Being off a little probably doesn't make any difference and it should not affect accuracy. Read the specs on your particular scope. I don't think I would want to use up more than 1/4 of the adjustment range just to get the reticle centered.
JMHO
Ray
B
BillPa
Guest
If you hold the objective lens against a mirror you'll see or may see two set of reticles. Adjust the scope until they align. If you count "clicks" you'll find 90% of the time its off using the mirror trick.
How its aligns on the rifle is another matter. Is the action straight, the barrel square to it, do the mounts actually fit, are the rings really the same height and etc. All those things need to be addressed.
M
MistWolf
Guest
If a scope is run too far in elevation or windage, it places the erector set close to the inside of the tube. This will limit adjustments. One feller couldn't bring his scope up enough in elevation to zero at 100 yards. The rifle had Redfield type mounts. We zeroed the scope by counting clicks, then zeroed the windage of the mounts in the bore sighter. The erector set then had enough clearance to adjust elevation normally.
Could you folks help me out with a clearer explanation of the two methods of scope centering- the V-block and mirror methods? Thanks
Could you folks help me out with a clearer explanation of the two methods of scope centering- the V-block and mirror methods? Thanks
Mirror Method
Never tried the mirror method. I will give it a try and then I can comment. The way I have been doing it, has worked well for over 30 years. I switched over to Burris Signature rings with offset inserts to correct any mounting alignment problems. The Burris sight has a great video that explains the use of their rings to correct alignment to receiver.
Never tried the mirror method. I will give it a try and then I can comment. The way I have been doing it, has worked well for over 30 years. I switched over to Burris Signature rings with offset inserts to correct any mounting alignment problems. The Burris sight has a great video that explains the use of their rings to correct alignment to receiver.
Last edited:
Fred Bohl
Retired Engineer
Re: “How important to accuracy is optically centering scope?”
As with all optical assemblies with multiple elements (lenses, air gaps and coated surfaces), the optimal arrangement for least distortion, aberrations and internal reflections has all elements on a single common optical axis. However, the basis of an internally adjusted scope is to purposely tilt parts of the internal optical path to adjust the windage and elevation to align the effective axis so that the POA and POI coincide.
The farther off the common optical axis, the more issues are created. As has been noted, if the windage adjustment to “zero” is a lot, that will restrict the available elevation adjustment (the converse is also true – large elevation offsets limit available windage adjustment). For almost all typical scope designs, the actual correction (1/4 or 1/8 minute) per click is only true very close to the optical axis and is a non-linear function of deviation from the optical axis.
However, let us not forget that the key to accuracy is that the POA and POI coincide. Therefore, unless we have adjustable mounts, multiple offset ring inserts (like Burris Signature Rings), shims or other means of external adjustment to align the scope to the rifle, we are forced to use at least some of the internal adjustment range to align or “zero” the scope to the rifle. As a consequence the typical scope will not have its internal adjustments centered when “zeroed”.
For those fortunate or foresighted enough to have external means to adjust the “zero” of the scope to the rifle and use the internal adjustments only for small field condition corrections, it is very important that the internal adjustments are centered before “zeroing” via external means. There are at least three methods to accomplish the centering of the internal adjustments:
1. Basic – Gently run the adjustment to one end of its range, count the clicks required to get to the other end of the range then back up half that number (repeat for the other adjustment). The principal advantage is that no other equipment is required but it is very difficult to do precisely particularly with scopes with large adjustment ranges and fine clicks.
2. Mirror – Place a mirror (first surface mirror preferred) on the objective housing. View through the eyepiece will show the actual reticule and its reflection. Adjust both turrets until the actual cross hair covers its reflection. This method is very precise but does require either a bright outdoor setting or sufficient room light to be able to see the reticule reflection.
3. V blocks – Place the scope on V blocks pointed at a white or gray card. While viewing through the eyepiece, rotate the scope. The junction of the crosshairs will orbit around the central axis. Adjust both turrets until the junction is on center and doesn’t move as the scope is rotated. Somewhat tedious but very precise and simple.
As with all optical assemblies with multiple elements (lenses, air gaps and coated surfaces), the optimal arrangement for least distortion, aberrations and internal reflections has all elements on a single common optical axis. However, the basis of an internally adjusted scope is to purposely tilt parts of the internal optical path to adjust the windage and elevation to align the effective axis so that the POA and POI coincide.
The farther off the common optical axis, the more issues are created. As has been noted, if the windage adjustment to “zero” is a lot, that will restrict the available elevation adjustment (the converse is also true – large elevation offsets limit available windage adjustment). For almost all typical scope designs, the actual correction (1/4 or 1/8 minute) per click is only true very close to the optical axis and is a non-linear function of deviation from the optical axis.
However, let us not forget that the key to accuracy is that the POA and POI coincide. Therefore, unless we have adjustable mounts, multiple offset ring inserts (like Burris Signature Rings), shims or other means of external adjustment to align the scope to the rifle, we are forced to use at least some of the internal adjustment range to align or “zero” the scope to the rifle. As a consequence the typical scope will not have its internal adjustments centered when “zeroed”.
For those fortunate or foresighted enough to have external means to adjust the “zero” of the scope to the rifle and use the internal adjustments only for small field condition corrections, it is very important that the internal adjustments are centered before “zeroing” via external means. There are at least three methods to accomplish the centering of the internal adjustments:
1. Basic – Gently run the adjustment to one end of its range, count the clicks required to get to the other end of the range then back up half that number (repeat for the other adjustment). The principal advantage is that no other equipment is required but it is very difficult to do precisely particularly with scopes with large adjustment ranges and fine clicks.
2. Mirror – Place a mirror (first surface mirror preferred) on the objective housing. View through the eyepiece will show the actual reticule and its reflection. Adjust both turrets until the actual cross hair covers its reflection. This method is very precise but does require either a bright outdoor setting or sufficient room light to be able to see the reticule reflection.
3. V blocks – Place the scope on V blocks pointed at a white or gray card. While viewing through the eyepiece, rotate the scope. The junction of the crosshairs will orbit around the central axis. Adjust both turrets until the junction is on center and doesn’t move as the scope is rotated. Somewhat tedious but very precise and simple.
M
MistWolf
Guest
Thank you for the explanations. I'll be sure to file them away in my notebook
Quote:
2. Mirror – Place a mirror (first surface mirror preferred) on the objective housing. View through the eyepiece will show the actual reticule and its reflection. Adjust both turrets until the actual cross hair covers its reflection. This method is very precise but does require either a bright outdoor setting or sufficient room light to be able to see the reticule reflection.
Unquote:
Fred Bohl:
Please explain what a First Surface Mirror I tried to check several of my scopes with the mirrors in our bath, but could only see the reticle in the low powered scopes. No success with the Weaver & Leupold 36's.
Fred J
2. Mirror – Place a mirror (first surface mirror preferred) on the objective housing. View through the eyepiece will show the actual reticule and its reflection. Adjust both turrets until the actual cross hair covers its reflection. This method is very precise but does require either a bright outdoor setting or sufficient room light to be able to see the reticule reflection.
Unquote:
Fred Bohl:
Please explain what a First Surface Mirror I tried to check several of my scopes with the mirrors in our bath, but could only see the reticle in the low powered scopes. No success with the Weaver & Leupold 36's.
Fred J
Stephen B Moore
New member
One shot- -
For a one time deal, try cutting "V" notches in an old
shoe box or such.
Steve
For a one time deal, try cutting "V" notches in an old
shoe box or such.
Steve
Fred,
What Mr Bohl is talking about is that the reflective surface is not behind glass but is directly on the facing surface. Mr Bohl apparently has a lot of knowledge of mirrors in telescopes or lasers. First surface mirror eliminates the bending of light as it passes through the glass to reflect and then pass back through the glass making the adjustment more accurate and easier as you don't lose as much refraction of light. Hope I got this right as it's been a lot of years. If I don't...Mr. Bohl...please correct me.
Also, for the higher powered scopes, holding a small lite in your mouth and shine it through the lens as your looking through it should brighten it up.
Hovis
Fred Bohl
Retired Engineer
Hovis,
You remembered near perfect and did a fine job of explaining the concept ++
For those of you that wish to use a mirror (even if not a first surface mirror) and are having problems with light level – put small spacers of the same thickness at two or three places between the objective rim and the mirror – this will allow some light in to help illuminate the objective side of the reticule and improve the visibility of its reflection. I use a couple of microscope glass slides and if you wet the slides they will stick to the mirror surface temporarily.
You remembered near perfect and did a fine job of explaining the concept ++
For those of you that wish to use a mirror (even if not a first surface mirror) and are having problems with light level – put small spacers of the same thickness at two or three places between the objective rim and the mirror – this will allow some light in to help illuminate the objective side of the reticule and improve the visibility of its reflection. I use a couple of microscope glass slides and if you wet the slides they will stick to the mirror surface temporarily.
First surface mirrors. Check with a local photocopier dealer to see if they are tossing out any copiers. the older ones (pre digital) all used first surface mirrors in the scanner assembly or there is a company callled (or was haven't checked recently) American Scientific loads of trash and treasure stuff along thesel lines.
Also note that these types of mirrors scratch very very easily, specticle cleaning supplies are about the easiest thing to obtain to clean them.
too many bullets+guns and not enough gas to get to the range.
Also note that these types of mirrors scratch very very easily, specticle cleaning supplies are about the easiest thing to obtain to clean them.
too many bullets+guns and not enough gas to get to the range.
Fred Bohl
Retired Engineer
First Surface Mirror Source
I would suggest the Edmund Optics MIRROR 4-6 WAVE EN AL 75MM DIA part number NT45-616 at $23.00 see: http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productid=1754&StartRow=21&PageNum=2
These are of more than adequate quality and the coating is actually very durable with modest care not to rub it with dirt or dust on it.
I would suggest the Edmund Optics MIRROR 4-6 WAVE EN AL 75MM DIA part number NT45-616 at $23.00 see: http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productid=1754&StartRow=21&PageNum=2
These are of more than adequate quality and the coating is actually very durable with modest care not to rub it with dirt or dust on it.
W
walt k
Guest
Very interesting. Thank you for the information. Question, is there any advantage in using the more expensive protected gold first surface mirror?
Fred Bohl
Retired Engineer
walt k,
The technique of using the mirror only requires that the mirror provides for sufficient quality of reflection of the back side of the reticule so that the user can position the reflected image behind the normal view of the reticule. Even a conventional float glass second surface mirror could be used but with some difficulty in the form of distorted or even multiple reflections.
I have found that for my high fixed power target scopes with fine cross hair reticules it is much easier to use a first surface mirror. I initially used one with a quarter wave flatness and composite coating but that version is quite a bit more expensive and the one I used was borrowed from a laser interferometer demonstrator. The ones I suggested in my last post are 4-6 wavelength flatness which is more than adequate for this purpose, have a more durable coating, are of a convenient size (75 mm diameter) and are low enough cost to keep one in my shop, one in the tool box at the range and one in my traveling range bag.
Higher quality surfaces and coatings may be desirable for many other purposes but add unnecessary expense unless of course you have better first surface mirrors available.
The technique of using the mirror only requires that the mirror provides for sufficient quality of reflection of the back side of the reticule so that the user can position the reflected image behind the normal view of the reticule. Even a conventional float glass second surface mirror could be used but with some difficulty in the form of distorted or even multiple reflections.
I have found that for my high fixed power target scopes with fine cross hair reticules it is much easier to use a first surface mirror. I initially used one with a quarter wave flatness and composite coating but that version is quite a bit more expensive and the one I used was borrowed from a laser interferometer demonstrator. The ones I suggested in my last post are 4-6 wavelength flatness which is more than adequate for this purpose, have a more durable coating, are of a convenient size (75 mm diameter) and are low enough cost to keep one in my shop, one in the tool box at the range and one in my traveling range bag.
Higher quality surfaces and coatings may be desirable for many other purposes but add unnecessary expense unless of course you have better first surface mirrors available.
S
Sitting Duck
Guest
I just used my wife's hand mirror and laid it flat on a table. Then I placed the scope on top in a vertical position and adjusted until the two images overlapped one another. Worked just fine.