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George,

Thank you for the review of my book "Tanami". List members may be interested
that the navigational  equipment carried included a Freiberger Yachting
Sextant which I purchased for the trip. I own several Plaths but they are
too heavy and take up too much space on a trip like this. The Freiberger
weighed only 860 grams.

It proved to be an inspired choice. The Yachting model is aluminium and
small (not to be confused with the full sized Freiberger sextant which has a
drum arrangement on the micrometer.) Interestingly Plath marketed a yachting
sextant in its heyday, small and light but unsuitable for terrestrial
navigation as it only reads to 90dd and is therefore an octant. In Australia
the sun is too high most of the year to much such an instrument practicable.

The Freiberger does not have a telescope but rather a 2.4x magnification
eyepiece which gives excellent service as the magnification is not too
great. Also the eyepiece can be unscrewed and the body viewed through the
eyepiece retaining ring, a great benefit when using an artificial horizon.
This is an excellent feature for terrestrial navigation and I am surprised
that the other makers such as Plath did not persevere with it.

I used several techniques on the crossing including observations of the sun
over several hours to get a three position-line fix albeit using only one
body, also double altitude shots of the sun at noon for longitude and
maximum altitude sun sights for latitude.

The sextant gave excellent performance and I was able to fix the position of
Mt Leichhardt in the eastern Tanami Desert to about 1 nautical mile.

Possibly most surprising is that the sextant had an index error of 0dd when
it arrived from the factory in Germany and despite being packed on a camel
saddle for 732km had the same index error when we finished. I found this
almost impossible to believe as on previous expeditions using pack horses I
found the index error varied every time I used the sextant. The sextant in
this expedition was extremely well padded being carried in a camel pannier-
a strong plastic box - shielded by packets of dried food. We chose the
quietest camel for the sensitive gear such as the sextant and the EPIRBS. We
also carried a Dolland Artificial Horizon c 1850 in its original box with
glass cloche cover and the glass was unbroken at journey's end. The motion
of the camel is rhythmic and unhurried and certainly these animals are
capable of carrying sensitive  gear long distances. Both mercury and water
were used to establish the horizon but I would be reluctant to take mercury
again due to its weight.

If anyone would like to read the full account they can purchase the book
from Dymocks bookstore in Sydney. Their contact is http://www.dymocks.com.au
Be warned it has a strong Australian bent and you would have to like reading
about deserts.

Kieran Kelly

6 David Place
Seaforth 2092
Sydney
Australia


ph     612 99079610
fax    612 99078232
mob  0411 261607


e mail kkelly@bigpond.net.au 


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