#### JAWZ

##### Well-Known Member

I have both a cosine indicator and a degree indicator which 1 do you prefer to use or find easier.

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I have both a cosine indicator and a degree indicator which 1 do you prefer to use or find easier.

If you use a ballistics program that accepts degrees as an input, naturally you want the device to measure degrees.

However, if you're using range cards, the cosine is more convenient because you just multiply the drop by the cosine.

Consider how you're going to use the 'look-angle' information, and that will tell you how you need it indicated.

-Bryan

If you would have 100" drop level, but shooting at 30deg,, 100*COS(30deg) would appear to be 15.4"

Where 100"*[1-COS(30)] would be 84.6" (I believe this).

The key seems to be where to insert the cosine into the eq'n..........

If you would have 100" drop level, but shooting at 30deg,, 100*COS(30deg) would appear to be 15.4"

Where 100"*[1-COS(30)] would be 84.6" (I believe this).

Mike,

I think you have COS confused with SIN (or degrees confused with Radians).

COS of zero degrees is 1.0 [cos(0) = 1] so if the look angle is zero degrees, you multiply the drop by 1.0 (no change).

If the look angle is 30 degrees, COS(30) = 0.87; so you would multiply the drop by .87.

If we applied your equation (drop*[1-cos(@)]), the drop would be zero for all level shots: drop*[1-1].

I'm pretty sure you multiply the drop by the COS (cosine) of the look angle.

-Bryan

My Bad.

My ACIs are in degrees, and I tend to think about it as I'm used to seeing it.

I enter degrees into a ballistic spreadsheet, that corrects PATH.

Basically adding DROP*(1-COS(@*PI()/180))

I'm taking care of the Deg/Radian part there..

But the Cosine ACIs pretty much take it to 'percent of' as indicated.

So there would not even be 30degs indicated with these, for that angle.

It's cleaner

My appologies to the poster, and Bryan thanks for the correction.

My ACIs are in degrees, and I tend to think about it as I'm used to seeing it.

I enter degrees into a ballistic spreadsheet, that corrects PATH.

Basically adding DROP*(1-COS(@*PI()/180))

I'm taking care of the Deg/Radian part there..

But the Cosine ACIs pretty much take it to 'percent of' as indicated.

So there would not even be 30degs indicated with these, for that angle.

It's cleaner

My appologies to the poster, and Bryan thanks for the correction.

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168 berger @ 3255 fps-- starting 3" high at 100yds, takes 16 min. IPHY elevation change at 1000yds. Shooting at a 30* angle the COS tells you 87% or 870 yds shot equivalent ( 12 min.IPHY)

Now going to Exbal and hitting the angle shooting function on ECCEL and looking at the chart for a 1000yd shot at 30* and it gives you 14.25 min. IPHY or the equivalent of 925 yds to make the shot !! This is because you still need to take into account the time of flight and the effects of air drag on the bullet for the entire distance ( 1000yds )----RHB

Multiplying the

Ultimately calculating a trajectory with degrees is the most accurate way, but the estimate provided by multiplying drop by the cosine is quite close.

As an example, consider a typical trajectory that's -314.3" low at 1000 yards for a level fire scenario. Incline the trajectory by 30 degrees, and the drop is now -271.4". If you approximate the drop by: -314.3" * cos(30) the answer is -272.2", which is only 0.6" different than the direct calculation.

-Bryan

Why not both?

Why not both...what? Do you mean to have a tool that gives both readings?

As for the original post, I prefer a cosine reading. That way I don't have to carry a conversion chart, need to convert that angle into a decimal. The only reason I can see needing degrees is that your ballistics program only allows you to use degrees. I use JBM at the house and I believe it will only let you inpute degrees. I can use cosine with exbal. If exbal goes down in the field I would multiply my drop for a given range (Improved Rifleman Method) by the cosine to get the corrected for gravity drop. The ballistic programs are supposed to be the most accurate due to effects of time of flight and such.

Why not both...what? Do you mean to have a tool that gives both readings? .....

Yes, Horus Vision have ASLI (Angle Slope Level Indicator) reads both cosine and degrees.

You can see it at WWW.MountsPlus.comYes, Horus Vision have ASLI (Angle Slope Level Indicator) reads both cosine and degrees.