New Posts New Posts RSS Feed - How do I use this scope?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Check GunBroker.com for SWFA's No Reserve and No Minimum bid firearm auctions.

How do I use this scope?

 Post Reply Post Reply   Topic Search Topic Search  Topic Options Topic Options
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/12/2009 at 15:19
mickey View Drop Down
Optics Apprentice
Optics Apprentice


Joined: March/28/2008
Status: Offline
Points: 99
Hi,
 
I'm a little (okay, very) confused with AO "side focus" scopes.
 
How would you zero a mil-dot scope that has a 30mm tube,  is 3-12x40 AO with side focus?
 
The literature says the parallax setting of the scope is from 10yds - infinity. Is this possible?
 
There are no yardage numbers on the objective end of the scope. The 3-12x is ring is forward of the ocular lense as usual.
 
Is the idea to zero it at, say, 25 or 50yds, then use the mil-dots to gauge longer shots? Or if you focus on a target say 100yds away, is the scope "automatically" zeroed to 100yds? This would be great but somehow I don't think this is so.
 
I have never owned or even seen a side focus scope in person. Is the side focus purely for getting a clearer "picture" through the scope and nothing else?
 
I guess what I want to know is this. What is the purpose of a side focus on a scope?
 
Does it replace the yard markers usually found on the objective end of the scope and if so, how? If it does not, why do manufacturers omit the yard markers on side focus scopes?
 
I have to quit now. I'm getting a headache.
 
The reason I didn't mention the specific scope is I'm afraid many of you guys will not answer these questions and just dismiss it out of hand because it costs less than $200.
 
Can we just pretend it's a Leupold and go from there?
 
One day I'll buy myself a nice Leupold. But it won't be anytime soon.
 
Thanks.
 
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/12/2009 at 16:10
RifleDude View Drop Down
MODERATOR
MODERATOR
Avatar

Joined: October/13/2006
Location: Texas
Status: Offline
Points: 14313
Side focus and A/O differ in appearance and location on the scope, but they both do the same thing -- focus the reticle and target image to remove parallax error, which occurs when the reticle and the target image aren't on the same focal plane.  Consequently, parallax gives the reticle the illusion that it is shifting on the target as you move your head position.  SF and A/O removes this error.  SF is a knob on the side of the W/E adjustment saddle in the middle of the scope tube, whereas A/O is a ring on the objective end of the scope.  The reason the literature says the scope has such a broad parallax setting is because that is the range the side focus parallax adjustment is supposed to compensate for. 
 
Mil Dots are primarily intended for ranging distant targets, but they can be used for holdover as well.  1 mil (milliradian) = 3.6 inches at 100 yards or 36 inches at 1000 yards.  Therefore, if you know the approximate size of your target, you can get a close approximation of distance with a mil dot reticle.  One example of a formula you can use for distance in yards is:  (object size, inches/36) X 1000 / # mils read = distance.
 
This is a good link explaining the use of mil dot reticles.
 
 
You would sight in a mil dot reticle the same way you would any other scope, using the center of the reticle as your point of aim.  Then, you can either use your reticle for holdovers once you understand your rifle's ballistics and verify at various distances, or dial in your firing solutions with the elevation knob after ranging with the reticle.  The side focus has nothing to do with adjusting your point of impact at distance; it is used to focus the scope so it is parallax-free at those distances.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/12/2009 at 22:12
mickey View Drop Down
Optics Apprentice
Optics Apprentice


Joined: March/28/2008
Status: Offline
Points: 99
Originally posted by RifleDude RifleDude wrote:

Side focus and A/O differ in appearance and location on the scope, but they both do the same thing -- focus the reticle and target image to remove parallax error, which occurs when the reticle and the target image aren't on the same focal plane.  Consequently, parallax gives the reticle the illusion that it is shifting on the target as you move your head position.  SF and A/O removes this error.  SF is a knob on the side of the W/E adjustment saddle in the middle of the scope tube, whereas A/O is a ring on the objective end of the scope.  The reason the literature says the scope has such a broad parallax setting is because that is the range the side focus parallax adjustment is supposed to compensate for. 
 
Mil Dots are primarily intended for ranging distant targets, but they can be used for holdover as well.  1 mil (milliradian) = 3.6 inches at 100 yards or 36 inches at 1000 yards.  Therefore, if you know the approximate size of your target, you can get a close approximation of distance with a mil dot reticle.  One example of a formula you can use for distance in yards is:  (object size, inches/36) X 1000 / # mils read = distance.
 
This is a good link explaining the use of mil dot reticles.
 
 
You would sight in a mil dot reticle the same way you would any other scope, using the center of the reticle as your point of aim.  Then, you can either use your reticle for holdovers once you understand your rifle's ballistics and verify at various distances, or dial in your firing solutions with the elevation knob after ranging with the reticle.  The side focus has nothing to do with adjusting your point of impact at distance; it is used to focus the scope so it is parallax-free at those distances.
 
Thanks (Rifle)Dude. I got it! That was a wonderful explanation; brief, concise and right to the point.
 
Mickey
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Similar Threads: "How do I use this scope?"
Subject Author Forum Replies Last Post
Scope for Henry Scope Mount laconiajack Rifle Scopes 6 10/30/2004 2:08:15 PM
Pick a scope, any scope.... huntincaleb Rifle Scopes 18 11/16/2004 4:05:37 PM
Using pistol scope for scout scope. cbighill Rifle Scopes 2 5/20/2007 9:15:31 PM
Yote scope wide FOV scope PappaBear Rifle Scopes 2
scope suggest 6X OR 8X fixed scope(mil dot) Rong1 Rifle Scopes 2
Scope and Scope mounts for a Savage 12fv .308 silentstorm16 Target 1
Scope, scope mount, stock for rem 700 ss varmint silentstorm16 Target 4
Scope Rings for a 50mm scope M7025-06 Rifle Scopes 3
Scope Features desired - what scope Sapper524 Rifle Scopes 8
AR-15 scope and 17 HMR scope, budget mr_blasto Rifle Scopes 15


This page was generated in 0.469 seconds.