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Speculum Metal Mirror, 1850-70

Speculum Metal Mirror, 1850-70

1850-1870
Speculum Mirror, 1861

Speculum Mirror, 1861

1861
Primary metal speculum mirror with central hole

Primary metal speculum mirror with central hole

1840-1850
Speculum Metal Mirror, 1840-60

Speculum Metal Mirror, 1840-60

1840-1860
Optical parts of Lassell's telescope

Optical parts of Lassell's telescope

1840-1850
Rough sketch of James Nasmyths' apparatus by which most perfect sound speculae may be cast with absolute certainty

Rough sketch of James Nasmyths' apparatus by which most perfect sound speculae may be cast with absolute certainty

1879
Optical parts of Lassell's telescope

Optical parts of Lassell's telescope

1840-1850
Primary speculum mirror of 13 1/4-inch diameter

Primary speculum mirror of 13 1/4-inch diameter

1840-1850
Speculum Mirror (dia. 5 3/4-inch) for Gregorian telescope in wooden box

Speculum Mirror (dia. 5 3/4-inch) for Gregorian telescope in wooden box

1750-1850
The first 48-inch speculum mirror cast with metal cover by Sir William Herschel in 1785 for his 'Forty Foot' telescope at Slough, England.

Original mirror for William Herschel's forty-foot telescope, 1785.

1785
Four primary metal speculum metal mirrors, three of 4 1/2- inch diameter and one of 8 5/8 inch mirror with central circular hole. Donated by Lieutent General A, de Gorloff who lived at Nasmyth's former home of Hammerfield near Penshurst in Kent. Four similar mirrors were originally donated but one was returned to be replaced by the larger one [see file for details].

Four primary metal speculum metal mirrors

1840-1850
Nine inch mirror of speculum metal (exact diam" 8 15/16 in) in tin cell with close fitting cover 9 1/2" diam, 1 1/2" deep, focal length 10' 1", cell and cover each painted " J"

Mirror of speculum metal in tin cell

1780-1820
Four speculum metal secondary mirrors thought to have been made by James Nasmyth. Donated by Lieutent General A de Gorloff who lived at Nasmyth's former home of Hammerfield near Penshurst in Kent.

Four speculum metal secondary mirrors thought to have been made by James Nasmyth

1850-1870
Experimental compound speculum mirror of 2 feet diameter, made by the 3rd Earl of Rosse. The 9 segments of speculum metal, are held in an alloy of copper and zinc.

Experimental compound speculum mirror of 2 feet diameter

1840-1845
Experimental speculum of 6 inches aperture and 24 inches focal distance, cracked across and bound together with string

Experimental speculum of 6 inches aperture and 24 inches focal distance

1840-1870
Optical parts of Lassell's telescope:- prism for 9-in reflector in green cardboard box; 3 multiple eyepieces; 5 small eyepieces; plane speculum on arm for 9-in; speculum for Newtonian finder in tin case 4 eyepices; 4 diaphragms (3 in two tin cases and one in wood case with metal lid)

Optical parts of Lassell's telescope:- prism for 9-in reflector in green cardboard box

1840-1850
Oval shaped secondary speculum mirror with cover, from the 6-foot Rosse telescope

Oval shaped secondary speculum mirror with cover

1845-1850
Two plane speculums by Lassell, with Lassell's M.S. directions

Two plane speculums by Lassell

1840-1850
Elliptical plane mirror (diagonal flat for Newtonian telescope) minor axis 1 1/2", major axis 2" in (full) soldered in usual way to circular brass disc, cylindrical cover of brass 1 3/4" deep, cover of brass 1 3/4" deep, cover and brass disc inscribed 1 "A4"

Elliptical plane mirror (diagonal flat for Newtonian telescope) minor axis 1 1/2"

1780-1820
Two plane speculums and two polishers by Lassell, with Lassell's M.S. directions

Two plane speculums and two polishers by Lassell

1840-1850