# NavList:

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

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Re: Lunar Distances with Alex's SNO-T
From: Alexandre Eremenko
Date: 2006 Nov 1, 19:47 -0500

```
Bill,
Can you suggest a testing range
in Greater Lafayette area where we can perform
Frabk's laser testing. (I will buy a laser level
for this purpose). We need a 500 feet flat place
with a table on one side and no people walking.

I see no other way to resolve the controversy with index.
Today experimented again with Frank's sextant.
IC from moon +0.65 4SD=66.7
True 4SD=65.6 (but no more than 66.0 in any case!)
IC from stars +0.2

Then shot Moon - Altair 4 times and got as perfect
sequence if IC=+0.2. Here it is
Errors: -0.1, +0.1, 0.0, +0.2
I consider this a strong argument agaionst the Moon method.

Then shot again Altair-Deneb: 38d00'7 (No IC applied)
while the truth is
38d00.2, so I have the usual overshot.
But in this case, IC from the Moon method givews the good
result.

Thus I have a well established pattern:
IC from stars is about +0.2 or +0.3
and this works well with the Lunars.

IC from Moon is about 0.6 to 0.7 and this works
well with star distances.

The only way to solve this contraversy
is to try the laser test.

Alex.

On Wed, 1 Nov 2006, Bill wrote:

>
>
> >> Alex has in the past looked poorly on natural horizon IE/IC.
> >
> > 1. Natural horizon is rarely so well defined as
> > a star or a Sun's edge.
> > 2. The Russian book "Precision of astronomical observations"
> > says that (based on large statistics) IC from horizon is much less
> > precise than that from the Sun.
>
> I'm sure the author of the study had performed more trials than I have, but
> the standard deviation (n-1) of my natural horizon IE checks--from a
> boat--are every bit as good as those of the sun from a chair.
>
> They do help to verify that my vertical sun IE checks (I believe due to
> astigmatisms) are too high.  Currently on the arc 0.75' on for sun,
> 0.3'natural on for horizon.  This syncs up with vertical sun IE checks done
> with glasses.
>
> I have confirmed this by standing on the Soldier's Home Road overpass (over
> Sagamore Parkway) looking east and using flat-top buildings, corn-refinery
> stacks and towers as well as the distant tree line.  A bit closer than I
> would like, but it should not cause more than a 0.1' error.
>
> It would appear that a good bit of the problems I have with consistent
> undershoots is using a sun-determined IC that is too high.
> >
> >> You have noted in the past that a bit of side error may be useful
> >
> > Later Frank corrected this statement. It can be useful for IC
> > checks with stars. But it is certainly harmful with Sun or Moon
> > checks.
>
> Understood, especially with your 4SD requirements.
>
> Bill
>
>
> >

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