Quote:
Originally Posted by skip
First a big thanks for making this guide
Just received my slide rule would have liked it a bit bigger, guess my old eyes cant cope so well these days.
Anyways in your range finding tutorial I have a query
I have the hairline set to 2.62 on the D scale
When I move the 1 on the C scale to line up with 1.9 on the D scale I can read under the hairline 1.39 (1390m) on the D scale.. All good
however you said when in periscope zoom to move the 4 mark on the C scale and line that up with the 1.9 on the D scale, when I do that I read 5.55 under the red hairline.
I assume that the 19mrads eg only applies to the x1 scope and in the 4x scope you would get a different mrad value which you would use with the 4 on the C scale.
Cheers
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Normally the scope is at 1.5x zoom and when zoomed in it is at 6x zoom, which is 4 times larger (6 / 1.5 = 4). This means that all objects you look at become 4 x larger but the scale of the graticules doesn't change.
So in our example the target with an angular height of 19 mrad would have an apparent angular height of 4 x 19 = 76 mrad when using 6x zoom. To find the range you still put the hairline over 26.2 on the D scale, but now you match 4 on the C scale with 76 on the D scale.
The range is still the same (1380m) and also note the 1 on the C scale is still pointing to 19 on the D scale. By the way, I think you put the hairline at 2.64 instead of 2.62, take another look.