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John

Very interesting.  In my primary (beginner's text) one of the positive
attributes of 211 was the use of one position (DR) for calculations of all
bodies.  The problems associated with long time spans (distances) between
observations was not spelled out IMHO.  In a conversation with Ken of
Celestaire (if I recall correctly), he stated/hinted that 90% of
observations were done using the Sun as the body.

Attempting to parse input to date (and admitting ignorance of other
variables) it would appear that while 208 has limitations similar to 214,
229, and possibly 249 (even lat and lon needed to enter the tables,
therefore potentially long intercepts) it is more user friendly to change of
position between observations.  211 is perhaps a bit more elegant for
multiple-body observations near the same time/position, but becomes a bit
more painful over longer time/position observations.

Is that a fair assessment?

Thanks

Bill

> I also have a copy of HO 208 and HO211 ( as well as some HO214 etc.)
>
> HO208 requires that an assumed position be selected so that the assumed
> latitude is an integral whole degree, and that the local hour angle is also an
> integral whole degree.  (Similar requirements to make at least one of these
> angles an integral whole degree is common to probably all of the commonly used
> inspection tables, HO214 for example)
>
> HO211 permits the use of a DR (dead reckoning) position.
>
> Both of these methods (HO208 and HO211) are relatively easy to use, and HO208
> is a smaller book.
>
> If a navigator is taking sufficient shots of several bodies over a relatively
> short time to obtain a fix, then either method will be effective.
>
> But if the navigator is using only the sun, taking a mid-morning sight, and a
> mid-afternoon sight, and advancing the line of position from the morning
> observation, then complications set in if the calculations are from an assumed
> position that is not the DR position.  Not to say that it cannot be accurately
> done, but that there are more chances for error.
>
> Therefore I prefer HO211, or the use of a electronic calculator using the DR
> positions.

   

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