Lummer-Brodhun photometer
Datecirca 1910
Inventory Number1997-1-1517
ClassificationPhotometer
Subject
Maker
Franz Schmidt & Haensch
1864-present
User
Biological Laboratories, Harvard University
founded 1932
Cultural Region
Place of Origin
Dimensions24 × 11.4 × 5.7 cm (9 7/16 × 4 1/2 × 2 1/4 in.)
Material
DescriptionThe type of photometer is a Lummer-Brodhun form with the so-called Lummer-Brodhun box. It has an opaque white screen visible through two swinging doors on either side of the box. The screen is removable by means of a small tab-like handle. The upper half of the box has 2 mirrors and 2 prisms that intercept and direct the light going to the eyepiece from the two light sources (outside the box).
The box is attached to a heavy yoke on which it can pivot. The yoke is threaded to take a bolt.
The box is attached to a heavy yoke on which it can pivot. The yoke is threaded to take a bolt.
Signedon plaque: FRANZ SCHMIDT & HAENSCH / BERLIN, S. / STALLSCHREIBERTRASSE, 4.
Inscribedon body: 280
FunctionThis instrument was used in comparing the brightness of an unknown source of light with that of a standard one. Light rays from the two sources enter on either side of the box. They first strike a white slab. Some of the scattered light on each side is reflected by mirrors towards what is called a Lummer-Brodhun cube, which consists of two right-angled prisms. What the observer sees in the eyepiece is two superimposed parallelograms on top of each other, one smaller than the other. When the brightness are identical, the two parallelograms become one. By moving the unknown light source farther or closer to the photometer, one tries to get rid of the two distinct circles. When this is accomplished, the luminosity of the unknown source can be calculated.
For a fuller description, see the following website.
For a fuller description, see the following website.
ProvenanceFrom the Department of Biology, Harvard University.
Zeiss-Aerotopograph
Date: circa 1950
Accessories: instrument is in original wood storage/carrying case. listed accessories: base plate, mirrors (2) and tubular holders (2), anchors (2), prism yoke, monocular adapter, lighting set with bulbs (3, one currently in lamp, its box in box of 2009-1-0002b), 2 monoculars (4 or 6 power) [6x24 (infinite) L or R Zeiss aerotopo logo), "fork"-shaped support (V rather), green filters (2) , dioptre lenses (2), strabismus-correcting lenses (2), photo holder, permanent magnets (8)
Object number: 2009-1-0002a
