Description
Astra IIIB Sight Tube (Clear Tube) is a simple sight tube used instead of a telescope on a sextant for astronomical navigation. The accessory provides a wide field of view and can make it easier to find and follow celestial bodies during observations.
A sighting tube – often called a clear tube – is used when optical magnification is not necessary, but where a larger field of view is an advantage. For example, this could be when measuring horizontal angles between objects, or when first locating the sun, moon or a star before possibly using a telescope.
The wide aperture provides a significantly larger field of view than a conventional sextant telescope. This makes it easier to keep the celestial body in the field of view when the sextant is moving, which can be useful when navigating with a sextant in waves or rough seas. Many navigators also use the sighting tube to more quickly locate celestial bodies for more precise observations.
The Sight Tube has been developed for the Celestaire Astra IIIB sextant, but is also suitable for several other modern metal sextants with a standard telescopic mount, including Astra III Professional and some models from Cassens & Plath.
This is a practical accessory for navigators who want a simple alternative to a telescope when sextant sailing, or who want to make it easier to find celestial bodies during observations.
Navigasjonsbutikken Kart.no AS is a distributor of Celestaire in Norway. For schools, courses and institutions, we can also deliver larger batches of sextants – please contact us for price and delivery time.
