NavList:

   

Reply

On May 9, 2004, at 4:52 PM, Robert Eno wrote:

> Fred Hebard wrote (a quote from Wharton & Field's):
>
>> For these observations in an artificial horizon, Wharton recommends an
>> eypiece shade rather than the swing-out sextant shades.  He also
>> recommends multiple eyepiece shades of varying optical density.  He
>> discusses examination of errors caused by swing-out sextant shades.
>>
>
> Robert responds,
>
> I don't know if I buy the bit about swing out sextant shades
> introducing
> errors. Perhaps this was true back when that book was written, however
> can
> the same be true for modern sextant shades?

and Fred:

You bet.

I heard of an example not too long ago of a modern, "quality"
manufacturer who shipped un-parallel shades.

The eyepiece shade avoids any swinging shade effects, including ones
that aren't there :)

At appropriate altitudes, swinging shades also will reflect a pretty
strong image of the sun right into the field of view.

Fred

   

Reply