Scope set up and range finding

Scope set up and range finding

Joined: February 11th, 2002, 6:01 pm

July 2nd, 2012, 8:22 pm #1

<p>Missed a few "should-have-been-a-gimme" shots on the gopher insurgency by the shop.</p><p>Figure my szero has shift some since the last formal zero session. No biggie. </p><p>side wheel on my Leapers SWAT 6-24 IR mildot was calibrated by marking off 10 - 60 yards in 5 yard increments in the field, then rotating the wheel one way till it focused, contiued till its out of focus, then bring the wheel back till its in focus again. Then mark the wheel with that yardage. Below Ken Hughes mentioned making the adjsutment in only one direction.... ?</p><p>Also, I did this late in the after noon, with the light slowly fading as I calibrated the markings. How likely is the changing light affecting the ranging?</p><p>TIA</p><p>dan</p>

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Last edited by dan_house on July 2nd, 2012, 8:24 pm, edited 1 time in total.
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Joined: October 27th, 2010, 4:43 am

July 2nd, 2012, 10:53 pm #2

just got a 3x12x44 Accushoot. I'm going to HR and do that. Put it on my CRX and marry them forever,til death do them part.
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Joined: September 19th, 2000, 4:18 am

July 3rd, 2012, 1:27 am #3

<p>Missed a few "should-have-been-a-gimme" shots on the gopher insurgency by the shop.</p><p>Figure my szero has shift some since the last formal zero session. No biggie. </p><p>side wheel on my Leapers SWAT 6-24 IR mildot was calibrated by marking off 10 - 60 yards in 5 yard increments in the field, then rotating the wheel one way till it focused, contiued till its out of focus, then bring the wheel back till its in focus again. Then mark the wheel with that yardage. Below Ken Hughes mentioned making the adjsutment in only one direction.... ?</p><p>Also, I did this late in the after noon, with the light slowly fading as I calibrated the markings. How likely is the changing light affecting the ranging?</p><p>TIA</p><p>dan</p>

dr_subsonic's pneumatic research lab
<img alt="[linked image]" src="http://img.photobucket.com/albums/v301/ ... od-1-1.jpg">
the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
He was referring to taking up any gear slop in focusing mechanism in one direction only and to place numbers on elevation wheel when sight picture is sharp. Some expensive sidewheels have little or no slop in focus mechanism.
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Joined: March 8th, 2009, 4:24 pm

July 3rd, 2012, 3:09 am #4

<p>Missed a few "should-have-been-a-gimme" shots on the gopher insurgency by the shop.</p><p>Figure my szero has shift some since the last formal zero session. No biggie. </p><p>side wheel on my Leapers SWAT 6-24 IR mildot was calibrated by marking off 10 - 60 yards in 5 yard increments in the field, then rotating the wheel one way till it focused, contiued till its out of focus, then bring the wheel back till its in focus again. Then mark the wheel with that yardage. Below Ken Hughes mentioned making the adjsutment in only one direction.... ?</p><p>Also, I did this late in the after noon, with the light slowly fading as I calibrated the markings. How likely is the changing light affecting the ranging?</p><p>TIA</p><p>dan</p>

dr_subsonic's pneumatic research lab
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the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
of focusing the entire visible spectrum (red,orange yellow,blue,green indigo, violet) on the same plane it could be effected by the time of day or overcast since the light tends to lean towards the red end of the spectrum at sunset and the blue end at sun up and when overcast.
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lhd
Joined: January 9th, 2002, 2:30 am

July 3rd, 2012, 4:11 am #5

So which scopes fit the bill Larry?
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Joined: March 8th, 2009, 4:24 pm

July 3rd, 2012, 12:58 pm #6

but very high quality photographic lenses are capable because many pro photographers won't tolerate soft focus in their images. i know my Hawke give a different range in overcast than in bright midday sun. about 1-2 yards.

the problem is called chromatic aberation. it exist at all times of day but is most noticeable early and late or when overcast. here is a discusion of chromatic aberationhttp://en.wikipedia.org/wiki/Chromatic_aberration

high quality photographic lenses are called "apochormatic". not sure if any rifle scopes are apochromatic. some expensive ones maybe.
Last edited by LARRYPIRRONE1 on July 3rd, 2012, 1:32 pm, edited 1 time in total.
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lhd
Joined: January 9th, 2002, 2:30 am

July 3rd, 2012, 4:41 pm #7

I may have learned a little there. I do believe it DOES confirm something I maintained some while back on these pages though, in that a longer focal length scope will be better than a shorter one.

As I glean from the article, it seems one might use the fringe aberrations as an aid in ranging, once they are studied enough.
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Joined: March 8th, 2009, 4:24 pm

July 3rd, 2012, 6:13 pm #8

when the target is in deep shadow because the light in deep shadow is at the far blue end of the spectrum and there is no other color of light present in deep shadow. that would cause the biggest focus error. It would be helpful to know how big that error is so one could correct for it. For instance if we know that the focus would be a certain % off in shadow we could correct. I noticed i missed an easy target down in the gully because the shadow caused a ranging error. I kind of wonder if this effects paralax in any way.
Last edited by LARRYPIRRONE1 on July 3rd, 2012, 6:17 pm, edited 1 time in total.
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Joined: February 16th, 2009, 8:33 pm

July 3rd, 2012, 7:08 pm #9

There was at least one thread on shooting the breeze (Brit FT forum) about ranging issues in Italy. Certain scopes didn't do so hot with certain colors, perhaps exacerbated by the lighting conditions. Maybe this is the chromatic issue you are referencing? Maybe Harold, Greg, Keith and company can comment on their experience over there and if they saw this at all with their respective optics.

http://www.shooting-the-breeze.com/foru ... lue+target

Some quotes:

"Blue light has a shorter wavelength. Comes to a different focus.
Get the same effect in our pipe range, it's made out of blue barrels, and the light inside is blue. Targets rangefind differently from being out in the open."

"Quite agree with Rich blue light used to play havoc with both PR Leups, Tascos, Niko and Burris, way under ranging."





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CASA Member - California Airgun Shooters Association: http://socasa.org
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Joined: January 1st, 2012, 11:50 pm

July 3rd, 2012, 7:13 pm #10

when the target is in deep shadow because the light in deep shadow is at the far blue end of the spectrum and there is no other color of light present in deep shadow. that would cause the biggest focus error. It would be helpful to know how big that error is so one could correct for it. For instance if we know that the focus would be a certain % off in shadow we could correct. I noticed i missed an easy target down in the gully because the shadow caused a ranging error. I kind of wonder if this effects paralax in any way.
I used to do some star gazing as a kid and chromatic aberration was the bugaboo of the refracting celestial telescopes that we were using. Reflecting telescopes were the better choice to minimize it. Mirror lenses don't get that prism affect since the light does not have to pass through it. Rifle scopes use a refracting arrangement. I wonder if they could make a reflecting rifle scope.

After shooting the pistol match where I had the pistol sitting in my lap and I had to crane my neck around to look in the scope, it made me think. A scope with the eyepiece at a 90 degree angle would let me look straight down at the scope without having to contort my neck. And make it a reflector scope.

Lately, I have been worrying less about the apparent focus and more about the parallax that I detect when I move my head. They don't always seem to coincide. Maybe that has to do with the lighting conditions, darker vs lighter.

I have one scope that gets a rainbow affect around the edges sometimes. I assumed that was the result of chromatic aberration but don't not know if it really affects it's use.
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