NavList:

No one that I knew trusted the moon sixty odd years ago, cheers, nsg

--- Robert Eno <enoid@northwestel.net> wrote:

> Gentlemen
>
> I'd like to throw this one out to the wolves.......er' list members, and see
> what comes back.
>
> Many navigation texts discuss what was apparently an "old sailor's tale"
> about the inaccuracy of moon observations. The story goes that in the old
> days, many navigators avoided moon shots because the believed that moon
> observations yield inaccurate LOPs; a belief which persists to this day in
> some circles. The texts go on to say that moon shots are perfectly accurate;
> no less so than any other body that one can observe; that with current
> correction tables, moon observations should yield results every bit as
> accurate as any other observations.
>
> Notwithstanding the pronouncements of navigators who have forgotten more than
> I will ever know, it has been my experience -- after thousands of
> observations of stars, planets, the sun and the moon, that moon shots do tend
> to yield results that are simply not on the money. I have tried to ignore
> this and embrace what the textbooks say about how moon shots are accurate,
> but the theory just doesn't pan out for me personally. I am one of those
> navigators who only uses the moon as a last resort because I fully expect
> (and am seldom wrong) that I will be wonky LOPs.
>
> Case in point: the other night, I took the opportunity to take some star and
> moon shots. Haven't seen the former since last April and while the return of
> the stars also signals the imminent return of old man winter in my part of
> the world, I nevertheless welcome the return of my old friends.
>
> To carry on, I took four observations of the moon and four of Vega (from a
> known position) using my Plath Bubble attachment.  As is my practice, when
> observing from a static platform, I averaged out the results of the sights,
> all of which were taken within minutes of each other.
>
> The average result for the moon shots was 3.9 minutes of arc error, while the
> results from Vega were only 1.3 minutes of arc error. To add insult to
> injury, the Vega shots were extremely difficult to take because the
> illumination system in the Plath, even at its dimmest, tends to all but wash
> out stars. The moon shot was a breeze but the results were pathetic. I should
> add that clouds were moving in at the time. Could clouds have an effect on
> refraction?
>
> Ok, Ok, I know that a bubble attachment is simply not as reliable as a true
> horizon and that 8 observations do not constitute a statistically-correct
> defence to support my assertion about the inaccuracy of moon shots. I merely
> presented these data to illustrate what has been my experience since I first
> picked up a sextant 23 years ago. It is more often than not, the same for me:
> to borrow from the modern pop culture vernacular: moon shots simply suck. At
> least for me.
>
> So what gives?  Have I been cultivating and reinforcing an as yet unknown bad
> habit vis a vis moon observations all of these years?  If so, why would this
> not be the case for the sun, stars and planets?
>
> Is there anyone else out there besides me who simply does not get good
> results from moon observations?
>
> Is this all in my head??
>
> Robert
>
>
>
> >


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around
http://mail.yahoo.com

--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---