# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: How to round?
Date: 2019 Jun 12, 21:02 -0400
Tony

You have essentially asked this question twice in a row.  First you were worried about the trigonometric identity series for your calculator, and now a question about rounding.  Both really ask "What about tiny values?"

You wrote Today I decided to try no-scope sight again, alas, refraction conditions were severe, even with the 7x I was "toward 2.5 nm", without a scope - no worse than that.

This refraction uncertainty is precisely why you need not worry about the tiny values.  At sea, you will not have the luxury of a known location with the ability to determine anomalous refraction.  So you always be under uncertainty.  In your case above, the rounding value you asked about (3 arc seconds) is FIFTY times smaller than your equivalent refraction at 2.5 nm.  Would 49x or 51x make any difference? No sir, it would not.

This is likely the reason you got the neutron answer.  There is no standard practice for your question, because it is completely irrelevant in outcome.

PS. Schrodinger's Cat does not like to be shipped with neutrons!!

On Wed, Jun 12, 2019, 7:48 PM Tony Oz <NoReply_TonyOz@fer3.com> wrote:

Brad, no, noodles make people overweight, I don't hang them. (Neutrons are even more dangerous - you'll get arrested in the first airport you visit - for smuggling of fissionable materials)

I asked because in CN most of the values are tabulated to the tenth of arcminute, I thought I must handle the calculations properly - hence my question.

By the way, since I got me a 7x (Keplerian) scope all (95%) my intercepts have decreased to ±0.2 nm. It's a big difference with where I started: 5~7 nm as a beginner with no scope, slowly getting to within 2~3 nm, then with a 3x (Galilean) scope I got to ±0.7 nm, and now this. Today I decided to try no-scope sight again, alas, refraction conditions were severe, even with the 7x I was "toward 2.5 nm", without a scope - no worse than that. I think - I'm making some progress. :)

Warm regards,
Tony

60°N 30°E

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