Star III Lantern for Group 'A' Roads
Single piece dome refractor lantern
Crompton Lamps :-
300/500W. | Tungsten filament | (GLS) |
125W | Mercury Fluorescent | (MBF/V) |
These simple but robust lantern embodies the following features:-
- Automatic focusing of lamp and registration of refractor.
- Bayonet fastenings for quick removal of refractor.
- Single piece prismatic refractor in two distributions.
300/500W GLS | G.E.S. | S160DS | S160DN |
125 MBF/V | G.E.S. | S160DS | S160DN |
Unless otherwise specified lanterns will be supplied with standard 1" B.S.P. tapping. |
Dimensions, Tapping & Weight |
Height | 12½" |
Diameter | 16" |
Tapping B.S.P. | 1" |
Minimum length of thread required | 1" |
Weight | 15 lbs. |
Refractor Catalogue Numbers |
Symmetrical | 4118 |
Non-Axial | 2/4118 |
1. Construction
There are only four main parts, viz. body casting, lampholder bridge assembly,
refractor and refractor retaining plate. The reflector is cast with the body which is arranged for top entry and provided with
two sets of tapped bosses for the attachment of the lampholder bridge assembly. This consists of a simple bridge piece, carrying the lampholder,
with bayonet slots to engage fixing screws provided in the bosses. They bayonet slots allow the bridge to be changed from one set of bosses
to anotehr or to be removed for wiring without the complete removal of the fixing screws.
The refractor is of the single piece dome refractor type with prisms moudled on both its internal and external surfaces. Projecting studs
from the refractor engage bayonet slots in teh refractor retaining plate which is itself screwed to the lantern body casting. The arrangement
of studs and retaining plate is such that the refractor can only be assembled with the correct angular location.
2. Material And Finish
Body | Silicon aluminium alloy LM6M, exterior finish aluminium, interior finish white and
underside of reflector white |
Bridge piece | Mild steel cadmium plated |
Refractor retaining plate | Mild steel sheradised |
Refractor | Crystal glass |
3. Distribution
Typical Polar Curves and an Iso-Candle diagram for the most popular 2/4118 non-axial refractor are given in Figs. 1 and 2.

FIG. 1
Polar distribution for 2/4118 refractor with 500W 7930-lumen lamp
A: In vertical plane through the centre of the main beam
B: Plan distribution of 78° cone

FIG. 2
Iso-candle diagram for 2/4118 refractor with 500W. 7930-lumen lamp.
4. Focusing
The bosses to which the lampholder bridge should be fixed for each lamp size are clearly marked within the lantern.
5. Maintenance
The aluminium alloy from which this lantern is cast is highly resistant to corrosion in both industrial and marine atmospheres.
Additional protection can be provided by occasional painting in service.
6. Optical Data For 2/4118 Refractor
| GLS | MBF/V |
Beam Angle Horizontal | 170° | 170° |
Beam Angle Vertical | 78° | 80° |
Light output ratio | 80% | 77% |
Light flux in lower hemisphere | 90% | 81% |
Directional Intensity Ratio | 5.6 | 2.6 |
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