Thorn Celest

Lantern acquired in January 2018.

This lantern was situated on Burley Close in Chesterfield, and was fitted to column 131037 as a replacement for a Beta 2 55 W SOX lantern. This column was, itself, replaced with a new 6 m column supporting a Thorn Civiteq LED lantern as part of Derbyshire's 'Invest To Save' LED programme; hence, the reason for my acquiring of the lantern. The Celest became Derbyshire Street Lighting's maintenance lantern for all 6 m columns requiring a replacement lantern in the early 2010s; taking over from the 70 W SON WRTL Arc lantern. Unlike some of Thorn's earlier offerings, the Celest only remained in production for a few years; its early demise brought about by rapid increases in LED technology, and the subsequent collapse of the market for street lighting lanterns employing a lamp.

The lantern is seen here in July 2015, not too long after it was installed.


I commented at the time that the combination of this lantern and hockeystick column created something of a 'Continental' appearance.


The Celest is a very shallow lantern, with a low profile bowl and streamlined design. It measures 847 mm (2 ft 9 3/8 inch) in length, 201 mm (7 15/16 inch) in width and 121 mm (4 3/4 inch) in depth. Inevitably, comparisons between its design and that of the legendary Philips MA SOX lantern range have been made, but then again, imitation is the sincerest form of flattery. Whilst the MA lanterns featured moulded GRP canopies, the Celest's is cast aluminium.


The NEMA photocell socket is located slightly off-centre on the lantern's canopy. Unfastening the two stainless steel clips that are normally flush with the contour of the canopy allows the bowl to swing open, being supported by the three hinges that are located on the other side. As acquired, the small screw securing the cover of the rear section was missing, but thankfully, I managed to find a replacement to the correct tapping (M3 or M3.5 - one or the other).


With this removed, the bracket support clamp can be seen. A curved spacer fits between the grub screws and the bracket, in order to cater for narrower bracket diameters (the grub screws supplied being too short to grip such brackets on their own).


The Zodion SS6 photocell fitted dates to May 2015, and is rated at 35 Lux.


With the photocell removed, the NEMA socket's manufacturing date is revealed - February 2013.


The lantern bowl does not incorporate any moulded refractor panels; however, its edge is marked by a narrow diffused section.


 As with many contemporary lanterns, the Celest can accept (either) a side-entry or post-top spigot, depending on the orientation of the hinged cover at the back of the lantern. Helpfully, the lantern's wattage is written behind this cover, though I suspect that this was more for identification prior to installation, as Derbyshire used 24 W and 36 W PL-L WRTL Libra lanterns at the time, which look similar, and could be confused.


The 55 W lamp takes up virtually the whole length of the optic. Despite this, the Celest can accommodate up to an 80 W PL-L lamp. Despite only seeing a few years' use, the lampholder is noticeably yellowed.


With the lamp removed, the thin metallic strip that acts as a support is revealed, as are several uncut alternative positions in the reflector. These positions would be used if the lantern ran a shorter, or longer, lamp.


The identification label is located at the far end of the reflector, and suggests that the lantern was manufactured at Thorn's Spennymoor, County Durham factory during week 37 of 2013: the 9th - 13th September.


Access to the lamp control gear is gained by releasing a clip at the front of the reflector / gear tray, and pulling the whole assembly forward. This should then hang down on two flexible plastic restraints located at either end of the tray, but in the case of this lantern, the restraints slipped through both holes. Strengthening ribs criss-cross on the inside of the canopy. The high frequency electronic ballast is located at the front of the tray, whilst the supply cable and NEMA socket are situated to the rear of the optic.


The Tridonic ballast combines the previously separate components of a wire-wound ballast, starter switch and capacitor.


The Philips-made compact fluorescent lamp was produced on the 20th May 2013 - a Monday, for those who wish to know.


Following a brief surface clean, the lantern was attached to a wall bracket on Sunday, 27th May 2018.

Not being impressed by the spacer method for securing the lantern to narrower bracket diameters, I decided to fit the lantern to a 60 mm bracket diameter instead, for a more secure attachment. This meant that the two grub screws protruded quite substantially beneath the lantern. The problem could be resolved with shorter screws, but as this arrangement doesn't bother me, I will keep with it.


Although bright when illuminated, the low luminous intensity of the long lamp ensured that glare was not an issue.


Lamp switch-on video:

Testing with my energy monitoring device revealed the following results.

Test Voltage (V) Current being drawn at full power (A) Measured wattage (W) Apparent Power (VA) Frequency (Hz) Power Factor True Power (W) Difference to rated wattage Percentage Difference
244.5 0.24 60 59 50 1 58.68 3.68 6.69%

WRTL (Indal) 'Vectra-X' 2661 | ELECO HW-747




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