Re: ST scale endpoint
Rick - WA6NDR
Thanks to all that responded, and I think there is enough here to address my original issue -- It appears that different manufacturers have used different math to generate their ST scales.
> because the value at that special tick is not printed, you still can't tell which formula it came from. ... nearly all trig scales are not marked in a way that you can definitively know what the value at the index is ...
We disagree here. I think 3 digits (5.71 to 5.74) can be differentiated by lining up the cursor with the index mark, regardless of the markings on the ST scale. For example, I have referenced the Pickett N-16-ES image that shows 5.74 at the index, with no ST scale mark at that value. But there is an index mark on the scale immediately above it. You can also see the 5.74 value by opening the image in an image viewer and zooming in.
> The ST scale is generally stressed for the trigonometric functions of small angles.
I agree, and that is why I think the best ST scale value to align with the index mark is (asin(0.1) + atan(0.1))/2 ~= 5.725 like the Pickett C 18-ES appears to use. (Zoom in and it try to get that 4th digit. It appears to me to be between 5.72 and 5.73.) But regardless of opinions about what is best, I think we've shown that different manufacturers have used different math to generate their ST scales. There is no universal standard value as there is with other scales like S and T.