Husun sounding sextant
Sounding sextant made by Henry Hughes and Son for sale in Canada.
Product details: Husun sounding sextant | Henry Hughes and Son | Quintant | Survey | Material: Brass
A Husun sounding sextant based on the type often used in WWII. The sextant has sealed mirrors, just as the later MkIII models had. The index mirror cannot be adjusted but the horizon mirror can. What makes this sextant special is the pentaprism supplied with it to allow it to measure angles over 140 degrees (up to 230 degrees). What makes this prism special is its location. On all my other sounding sextants with a prism (except for the Observator) the prism is located behind the horizon mirror but on this sextant it is just in front of the telescope.
Just looking at this contruction in the photographs may make one wonder if this will ever work as the prism all but blocks the telescope. However, this set-up uses an optical 'trick' in that a telescope will direct any of the light falling on it towards it focal point. As the prism is 'on legs' part of the bottom part of the telescope is not obscured. This is the part from where the rays bouncing of the index mirror via the horizon mirror come from. As a result, the index mirror can still be used and the 90 degrees is obtained from immediately behind the telescope at the same 'height' as the index mirror making the them almost coincide optically.
The instrument has belonged to the Royal Canadian Navy and was employed, as mentioned on the box, in the 'net laying'. Net laying is determining the main control points for the survey so that these can act as reference points during the hydrographic part of the survey. This sextant seems to have been used out of Nova Scotia and more particularly Halifax.
Husun canadian sounding
Data sheet
- Year
- 1939
- Serialnumber
- 21933
- Type of use
- Survey
- Material
- Brass
- graduation
- deg
- measuring range
- 125 / 215
- Radius limb in mm
- 145
- accuracy
- 0.3'
- fine reading
- drum micrometer
- image direction
- upright
- Size instrument (l x w x h) in m
- 0.25 x 0.28 x 0.22
- weight instrument in kg
- 2.1
- Size case (l x w x h) in m
- 0.28 x 0.33 x 0.16
- weight case & in kg
- 3.7
- country obtained from
- Canada
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Sounding sextant made by Henry Hughes and Son for sale in Canada.
Product details: Husun sounding sextant | Henry Hughes and Son | Quintant | Survey | Material: Brass