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Cassens and Plath Sextant Astigmatizer Lens

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  • Expands the point-shaped celestial object to a horizontal line
  • For all horizon mirrors
  • For Cassens & Plath sextants only
  • For subsequent mounting




The star astigmatizing lens spreads the point-shaped celestial body to a horizontal bar. In addition, a tilt of the sextant is immediately detected.

The star astigmatizing lens can be attached to the sextant as a 5th glass in index direction and can be used with all horizon mirrors.

The glass can be easily retrofitted to all Cassens & Plath sextants.

Full view without astigmatizing lensFull view with astigmatizing lens
(without tilting)
Full view with astigmatizing lens
(with tilting)

If the astigmatizer is swung into the field of view a star is not longer seen as a light dot but as a horizontal light stripe. The horizon view is not altered because the astigmatizing lens is located at the index shade position.
It is recommended to make some exercise star shoots to become familiar with the appearance of the stars and especially of the sun.

The function of the astigmatizing lens is that of a level indicator, too. With it the navigator will have the right vertical orientation of the sextant to get accurate star shoots. The right orientation may be recognized by the parallel of the light stripe and the horizon.

Furthermore the elongation lens simplifies observations of fixed stars because it is much more ergonomic to observe a light stripe but a light dot.

If the lens is used in combination with a traditional half silvered horizon mirror the spread light reaches the horizon area. This makes that somthing like a fullview effect is visible: The star light and the horizon are seen to be superposed.

Additional information

Weight2 lbs



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