ZERO MAGNIFICATION SIGHT TUBE
It used to be good sextants came
with one of these. They were also called clear tubes, and hooded peep sights.
They are used primarily for taking horizontal angles where magnification
is not normally needed, but where a wider field of view is helpful in identifying
objects with respect to one another. They are also used for celestial observations
in rough weather, where a wider field of view is helpful in holding the
object in sight despite sextant movement. It also makes it easier to initially
acquire celestial objects. If for example you normally use a 4 power telescope,
the sight tube gives you 3 to 4 times more field of view than you would
have with the telescope
We have had many requests for the
Sight Tube, and are told that some people simply find sextants easier to
use with it than with a telescope of any kind. Although the Sight Tube
was designed specifically for the Astra IIIB sextant, it also functions
perfectly on most other metal sextants having a standard telescope mounting
slot.
The Sight Tube is made of durable,
high temperature resistant plastic The interior is dulled to reduce distracting
reflections. The exterior is finished in a matte black to match the finish
of most sextants. The slip-on rubber eyecup (Item #0505) fits on it. It makes a good accessory at a very low cost. SW 0.1 lb
