A combined sun & star diagonal, designed by Alexander Clarkson, made by W. Watson & Sons of London, circa 1925.

R.A.S. standard 1 1/4 inch thread.

With associated parts.

Marked: “SUN” & “STAR” DIAGONAL. – W.WATSON & SONS, LONDON.

9 x 7 x 4.5 cm.

Literature: A Catalogue of Astronomical Telescopes and Accessories. W. Watson & Sons, Ltd. Page: 21. (Code word. TEMPY).

W. Watson and Sons Ltd, Opticians.

313 High Holborn, London, and Edinburgh.

Works: Bells Hill, High Barnet, Hertfordshire.

1837 Founded in 1837, and in 1900 acquired John Browning & Co.

For more information on combined sun and star diagonal see the paper written by Chris Lord:

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/SUN&STAR_DIAGONAL.pdf

A Catalogue of Astronomical Telescopes and Accessories. W. Watson & Sons