Next message: Peter Fogg: "Re: GPS shortcomings."
Peter Fogg wrote:
>>On Behalf Of Lu Abel
>>
>>We're talking about the sextant being a backup navigation instrument,
>>not the primary one, so I must ask why you think a Davis Mk 15 or Mk 25
>>wouldn't be up to the task.
>
>
> Metal is more reliable. Won't warp and is less liable to temperature
> effects. Nothing new or controversial here.
Do you speak from experience or just theory about "plastic?"
My understanding is that Davis's are made out of a form of "engineered"
plastic that is very strong and has virtually no temperature coefficient
of expansion. I'll agree "metal is more reliable," but by how much? I
have co-taught USPS's celestial courses for many years and about 90% of
our students have used Davis sextants. In years of checking sights I've
never run across one that was off because the sextant was off -- any
errors have always been traced to student error. My own Davis Mark 15
is almost two decades old and has never given me a problem.
Lu Abel
