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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
How accurate are angle cosine indicators?
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<blockquote data-quote="dwm" data-source="post: 17434" data-attributes="member: 1136"><p>Gravity only applies during the time of flight that the bullet is traveling in the horizontal distance to the target.</p><p></p><p>The distance to the target measured by a laser range finder = the hypotenuse of a triangle.</p><p></p><p>The horizontal distance to the target = laser measured distance * cosine of the angle</p><p></p><p>Example:</p><p></p><p>Target at 30 degrees up and 600 yards away as measured by laser range finder</p><p></p><p>Horizontal distance = 600 yards * cosine(30) = ~520 yards</p><p></p><p>So instead of calculating bullet drop/clicks for 600 yards you calculate bullet drop/clicks for 520 yards.</p><p></p><p></p><p>Cosine table:</p><p>Angle: Cosine of angle: Cosine(angle) * 600 yards</p><p>0 1 600 yards</p><p>5 0.9962 597 yards</p><p>10 0.9848 590 yards</p><p>15 0.9659 580 yards</p><p>20 0.9397 563 yards</p><p>25 0.9063 543 yards</p><p>30 0.8660 520 yards</p><p></p><p>Something to note here is that the cosine of small angles (0 to 5 degrees) is very close to 1 and can be ignored.</p><p></p><p>So either do the math or take a spotter shot.</p><p></p><p>Hope this helps.</p><p></p><p></p><p>One more thing - if you have a MIL-DOT reticule, the MIL-DOT Master provides a quick way to calculate all of these issues including effects of the wind:</p><p></p><p>About the Mildot Master® (<a href="http://www.mildot.com/" target="_blank">http://www.mildot.com/</a>)</p><p></p><p>The Mildot Master® is an analog calculator designed along the principle of a slide rule, utilizing logarithmic and inverse logarithmic scales developed specifically for performing the following operations:</p><p></p><p>- Rapid and simple calculation of range to target, based on a measurement of the target with a mildot reticule, by aligning the estimated target size directly opposite the mildot measurement, and then reading the range at an index mark. </p><p></p><p>- Rapid and simple calculation of the amount of sight correction necessary to compensate for bullet drop and/or wind drift for a given range, enabling the shooter to determine either the equivalent telescopic sight adjustment (minute-of-angle, or MOA) or the equivalent hold-over (mils), by reading equivalents in both MOA and mils directly opposite the bullet drop/wind drift figure.</p><p></p><p>- Additionally, angle of fire for uphill or downhill shots can be accurately measured, and the up/down compensation can be closely calculated to reduce the errors such shots can induce. </p><p></p><p>Doug</p><p></p><p>[ 11-28-2003: Message edited by: dwm ]</p><p></p><p>[ 11-28-2003: Message edited by: dwm ]</p></blockquote><p></p>
[QUOTE="dwm, post: 17434, member: 1136"] Gravity only applies during the time of flight that the bullet is traveling in the horizontal distance to the target. The distance to the target measured by a laser range finder = the hypotenuse of a triangle. The horizontal distance to the target = laser measured distance * cosine of the angle Example: Target at 30 degrees up and 600 yards away as measured by laser range finder Horizontal distance = 600 yards * cosine(30) = ~520 yards So instead of calculating bullet drop/clicks for 600 yards you calculate bullet drop/clicks for 520 yards. Cosine table: Angle: Cosine of angle: Cosine(angle) * 600 yards 0 1 600 yards 5 0.9962 597 yards 10 0.9848 590 yards 15 0.9659 580 yards 20 0.9397 563 yards 25 0.9063 543 yards 30 0.8660 520 yards Something to note here is that the cosine of small angles (0 to 5 degrees) is very close to 1 and can be ignored. So either do the math or take a spotter shot. Hope this helps. One more thing - if you have a MIL-DOT reticule, the MIL-DOT Master provides a quick way to calculate all of these issues including effects of the wind: About the Mildot Master® ([url]http://www.mildot.com/[/url]) The Mildot Master® is an analog calculator designed along the principle of a slide rule, utilizing logarithmic and inverse logarithmic scales developed specifically for performing the following operations: - Rapid and simple calculation of range to target, based on a measurement of the target with a mildot reticule, by aligning the estimated target size directly opposite the mildot measurement, and then reading the range at an index mark. - Rapid and simple calculation of the amount of sight correction necessary to compensate for bullet drop and/or wind drift for a given range, enabling the shooter to determine either the equivalent telescopic sight adjustment (minute-of-angle, or MOA) or the equivalent hold-over (mils), by reading equivalents in both MOA and mils directly opposite the bullet drop/wind drift figure. - Additionally, angle of fire for uphill or downhill shots can be accurately measured, and the up/down compensation can be closely calculated to reduce the errors such shots can induce. Doug [ 11-28-2003: Message edited by: dwm ] [ 11-28-2003: Message edited by: dwm ] [/QUOTE]
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How accurate are angle cosine indicators?
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