mailing list
site map

Alpha One on 2551 steel column
atlas alpha one
sodium lantern

For the lighting of main highways and motor-roads the Alpha One sodium lantern is particularly suitable. Street lighting engineers everywhere will appreciate its unique features, such as the Opticell described below, its superb construction and its clean, modern appearance. It was awarded a Gold Medal at The Eleventh Milan Trienalle of Architectural and Industrial Art and has been accepted by the Council of Industrial Design for Design Index.


Special Features. The hermetically sealed lamp enclosure and light control system - the Opticell, is a unified assembly of two plastic mouldings, a reflector with the lamp support and two support pins. The sodium lamp is inserted through an aperature at one end which is then tightly closed by a combined lampholder and sealing cap held place by two quick-release clips. By this method the interior is completely sealed and very considerable periods will elapse before attention other than lamp replacement is necessary.

The support pins engage with slots in the end support. Releasing a special retaining toggle allows the Opticell to be easily hinged down to give ready access to the sealing cap. The end support and sealing cap are corrosion resisting.

Optical System. Based on the principle that, to achieve maximum effeciency, light from the source should be redirected as little as possible to achieve the desired distribution, the Atlas Light Control system ensures a highly satisfactory optical performance. It is acheived by careful siting of the various elements of the Opticell. The use of a high proportion of reflecting prisms ensures effective control with the lamp in this position.

Because the globe is hermetically sealed the prisms do not, of course, require additional protection and are therefore moulded on the interior surface of the Opticell.

Materials. The Opticell is made from a special heat-and-weather-resisting grade of clear plastic which has been developed specially for this application. The end support is corrosion-resisting aluminium alloy and other metal components are of carefully selected grade of stainless steel or aluminium.

Finish. The plastic globe is treated with an antistatic compound. Aluminium parts are either anodised or subjected to a "Bonderite" process before beign stoved to a matt aluminium.

Installation. The end support has an entry for a 4½" length of 1½" unthreaded barrel. A spirit level platform is incorporated into the Opticell to obtain accurate levelling. This is achieved by the adjustment of the three 3/8" B.S.W. hardened socket set screws that grip the barrel.

Wiring is brought to a heavy-duty porcelain terminal block and from this a flexible P.V.C. cable, clamped at each end, passes to the sealing cap.

Catalogue Numbers.

PSD/E 1085 lantern for 60W SOX or 85W SOI lamps.
PSD/E 1140 lantern for 100W SOX or 140W SOI lamps.

Lamps. Atlas 60W or 100W SOX, 85W or 140W SOI.

Polar diagram round major axis for 140 watt lantern with a light output from the lamp 12200 lumens.
Technical Data

ATLAS Sodium Vapour Discharge Lamps:140 watts
Average light output throughout life:12200 lumens
Angles of elevation of 90% peak intensity in principle plane:65° - 79°
Peak Intensity Ratio:2.1
70% of Peak Intensity Ratio:1.5
Intensity Ratio in 0° to 30° zone:1.0 - 1.2
Elevation above peak of intensity ratio of 1.2:82°
Horizontal Intensity Ratio in plane parallel to road:0.55
Angle of Azimuth of Peak:
Flux below horizontal in lumens:9150 lumens
Total circuit rating:165 watts
Mounting heights for Group A2 roads:25ft, 30ft.
Mounting heights for Group A3 roads:25ft, 30ft.
Conversion factor for 100 watt SOX lamp0.89
Conversion factor for 60 watt SOX lamp0.53
Conversion factor for 85 watt SOI lamp0.55
Overall length:28¾ ins. 73.5 cms.
Overall width:9½ ins. 24.1 cms.
Overall height:7¼ ins. 18.4 cms.
Weight:9lbs. 4.1kg.