Can a scope have internal crossover error?

Discussion in 'General Airgun Chat' started by KeithW, Dec 17, 2018.

  1. mrgeoff

    mrgeoff Active Member

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    Same for this, does the scope really want to be optically centred on the horizontal axis for this to work best? Or does this tool show you if it’s not zero, hence better than mirror method?

    Thanks!
     
  2. RobF

    RobF Administrator Staff Member

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    Simply by looking above and below the crosshair can't affect where the pellet lands unless that reticule isn't inline with the fall of the shot.

    The reticule is focused to the exact point where the image is focused, assuming the parallax is set correctly. The eyebell does nothing in this except focus your eye to the reticule.

    So if you are not dialing and using holdover then it's one of 4-5 things :

    Wind, and an incorrect windage setting.
    Cant.
    Reticule not in line with the bore while vertical above it.
    Parallax error.

    And if you are dialing, then it could be a misaligned reticule.

    But the likely ones are the first 4. I've never seen a decent scope make not track except for when the windage was at the extreme of it's travel.

    If we shoot indoors then we can say the fall of the shot is vertical, therefore if the reticule doesn't follow it up and down, it's either not vertical, or you're not parallaxed to the ranges up and down the ret. This is easily done if you don't change the parallax for each range you test at. If outdoors, it can be wind. And in both it can be cant added to it as well. 5 degrees of cant is enough to see a significant shift the likes of which you describe. It's also nigh impossible to spot without a level especially outdoors...
     
  3. Evo

    Evo Scouser by Birth mfta shooter by choice

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    correct me if i,m wrong but i thought hft was only to 45yrds ???? was just reading a previous post, enjoying this thread because i,m just setting my nikko up on my tx200
     
  4. KeithW

    KeithW Barn door? Where?

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    Yes, Evo, UKAHFT is to 45yards. However to check for grouping and lateral setting I sometimes shoot longer, furthermore the Cambridge HFT Ultimate Series (second round this coming Sunday 23rd) shoots out to 55yds.

    No Rob, not dialling.

    I think perhaps I should bring myself back to basics and make sure my parallax is set at my zero. But the thing is with relatively low mag scopes there can be quite long depth of field. Next time I feel strong enough to settle in for a session of hair-tearing with the Vortex, I'll wind it up to the full 12x when I set my parallax!

    I've put a Hawke Panamax 4-12x50 on [yes I know, not ideal for HFT ... it was the first one that came to hand that wasn't already mounted on one of my rifles], using different mounts, and it seems fine. And my goodness! it really ensures you centre your pupil!
     
    Last edited: Dec 20, 2018
  5. RobF

    RobF Administrator Staff Member

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    Hi Keith

    If you suspect parallax bob n weave your head behind the scope and see if the reticule moves across the target. Ideally put the gun on a bench and don’t move it... maybe remove the cheekpiece to allow more movement. Remember though that you need to correct the parallax for the other ranges you shoot, you can’t leave it set for one range.

    If it works when the parallax is set for each range but doesn’t when you leave it at your normal setting it could suggest eye alignment is the issue. The mention of the need for a tighter position for the new scope suggests this could be an issue. Although you can see a picture with the other scope if your eye isn’t centred then you will see poi shift due to parallax error at ranges away from where it’s set. Apologies if I’m tryinb to teach granny.
     
    KeithW likes this.
  6. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    Spot on Scott, exactly what you do.
    It's also useful for checking an existing set up as you can stick the unit in the barrel an see straight away if the scope alignment is out. People talk about it giving a 'rough' zero but in my experience if you spend the time to align everything the zero is usually spot on from the off maybe only needing a couple of elevation clicks at most.
     
  7. david j

    david j Member

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    Where can I buy a reflective collimator please.
     
  8. Scott Hull

    Scott Hull Member

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    I recently bought a Bushnell magnetic collimator:

    https://www.amazon.com/Bushnell-740001C-Magnetic-Boresighter/dp/B001C5ZRMI

    Since it attaches with a magnet rather than a "spud"/arbor, it depends on the user to center it up. For checking scope rotation (scope-cant), I found it no better than the mirror method. But the collimator works very well for checking scope tracking with respect to the reticle. Bushnell also makes a professional collimator which probably works better but will require an arbor in the bore.

    If you don't mind inserting an arbor into the bore, a laser bore-sighter (laser collimator?) works well enough. I have one of those as well.

    The laser can also be used to check turret tracking but you will need to do it outside using graduations on a target.
     
  9. david j

    david j Member

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    Cheers Scott.
     

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