As a lighting industry and profession, through LED technology we have made huge strides in reducing energy use and carbon emissions. Our next challenge is reduce light pollution to safeguard wildlife and protect people’s enjoyment of star laden Dark Skies.

Our two speakers in this webinar will share some context driving these issues, and show pilots of good practice in public realm and business property lighting from Cumbria, the Lake District and the North York Moors Dark Sky Reserve. We can work together across different interests to mainstream Dark Sky compliant lighting both in the North of England and UK-wide.

Speakers: Jack Ellerby, Dark Skies Cumbria Project Officer at Friends of the Lake District and Mike Hawtin, Dark Skies Project Manager for NYMNP.

Hosted by: Ray Keane BSc IEng MILP – Chair, ILP Durham.


What is the recommended highest colour temperature?

MH: For our IDSR application the IDA specified a maximum of 3000k though we aim for 2700k where product exists. There are very few products available below 2700k. The IDA have now dropped this to 2700k as a minimum for applicants but there are signs that thus may come down to 2200k. The biggest issue we have here in the UK is that very few products exist at these levels so this is a big challenge for us.

JE: The IDA Guidance 2018 for Dark Sky areas recommends 3,000K or lower, however, as manufacturers respond to the growing evidence of the impacts of higher blue-white spectrum LEDs spectrum warmer colour temperatures are coming on stream. The IDA adopted principles in January 2021 recommending 2,200K. See:

Are these lights been dimmed to prescribed lighting classes or just arbitrary values. I also assume where the lights are being switched off the areas are not used when the lights are turned off?

MH: We have a number of rural villages where dimming or part night street lighting has been in place for a while. At certain times (usually midnight to 5am) the lights will not be on and residents are happy with this. When looking at residential/commercial lighting we stipulate there are no ‘always on’ lights and that sensors are used so areas are lit only when needed. If nobody is there, no light is needed. Our rural crime coordinator also pushes this message. Always on lights show what’s on offer and you don’t know if somebody is there who shouldn’t be. For all rural businesses, shielded lights should still be used and lights only on during opening/operational hours.

JE: I am not aware of prescribed dimming other than GN01 Table 4. The level chosen is not arbitrary taking into account a mix of factors, such as energy saving values, experience from previous initiatives and research linked to ecological impacts. With the human eye the vast majority of people cannot detect dimming.

Yes our pilot part-night switch off in a quiet rural village with virtually no activity after 12pm, not uncommon across many sparse rural areas, hamlets and small villages.

Have you experimented with reducing lighting levels as well in any of your projects?

MH: We aim for the lowest possible lighting levels to meet the need in all projects. Lighting should be enough for the application and no more. Our LMP offers general guidelines on total lumens output based on property size.

JE: When you say ‘level’ I presume you mean overall volume of lighting? With the cost of electricity and demand only going one way, and public finances reducing around ‘public space and infrastructure’, we all have to think can ‘less be more’. So yes where we can reduce the extent of lighting we’ll take that opportunity, especially where local communities want and support that approach.

Zero upward light must mean exactly that. No light above the horizontal plane. How are you verifying true 0% ULOR?

MH: At present there’s no specific accreditation marque in the UK (the IDA accreditation is very US focussed) so any 0ULR rating is quoted by the manufacturer or by virtue of the fact the lamp/led is recessed inside the housing. Of course, this doesn’t stop reflected light so that is an additional consideration.

JE: Post installation spectrometer readings where possible.

Satellite data has issues with picking up the blue wave length from LEDs. It’s worth being cautious about current data as it may well paint a better picture than the reality?

MH: Yes we need to be careful and consider other ways of measuring improvement. Following the principles of fully shielded, warm colour temperature and effective controls (sensors/timers) we can still make tangible improvements, we may not always be able to measure that improvement.

JE: Good point. Yes I have sort expert advice which indicates upward of 30% of blue-white LED content is not picked up by the VIIRS Satellite, compared to short-wave length  old sodium lights at approx. 1,800K.

Satellite imagery is a powerful visual communication tool, especially as with lighting which can get very site-development in focus. For example, when I shared the image looking down on Cumbria with Sellafield Ltd they were shocked to see their lighting footprint was as large as Barrow in Furness and, therefore, were keen to act to make a positive difference. Each method of measuring light pollution and sky quality has caveats and limitations. We use Sky Quality Meters extensively, but human error and changes in weather can affect those readings significantly. The human eye itself takes some beating in my humble view!

In the second presentation what were the value range of the coloured dots, the darker the colour was indicated as being darker?

MH: The SQM readings in mag/arcsec squared . Blue is 21.5-21.8. Dark Green is 21.2 – 21.5. Light Green is 20.9 – 21.2. Yellow is 20.4 – 20.9.

Are the HEA and LIA being lobbied to provide more suitable solutions? Seems to me, shortage of suitable residential solutions too.

MH: We’re definitely short of quality residential solutions. We end up sifting through cheaper products to find suitable compliant residential lighting.

JE: Certainly, through the IDA, UK Dark Skies Partnership and APPG for Dark Skies we are engaging positively with the LIA. We have not touched base with HEA – good shout, thanks.

While I commend the approach of reducing light pollution in dark sky areas, is there a strategy for reducing light pollution from urban areas? The “sky glow” from cities can been seen far beyond its limits.

MH: I agree that town and city sky glow is very much an issue. Our planning department has a heads of planning forum with other local authority planning departments. It’s a slow process of convincing and protecting our boundaries in the first instance. Cities will need legislation as well as education to improve.

JE: Absolutely, certainly I am working Cumbria-wide and the APPG for Dark Sky’s 10 Policy Plan recommended establishing a Town and City Dark Sky initiative for this very reason. As Mike said the ground swell is quite astounding and groups are forming all over the UK and internationally, for example in London.

Is current product cost a big deterrent to councils embracing the dark sky ethos?

MH: Right now, no. 5 years ago 3000k LEDs cost much more to run than 6000k/4000k but now the difference is negligible. However, they have now committed stock for 3000k installations in protected areas so calls to lower this to 2200k in the near future are likely to cause some issues.

JE: Yes to the extent some of the best products are not in mainstream manufacture yet, but LED technology is flexible and new products are coming into the market weekly.

The barrier is really addressing legacy lighting systems in the context of local authority falling budgets. Funding is available through linked to carbon and energy saving and biodiversity action plans. For example, the Lake District Foundation has a Low Carbon Lake District Fund that does cover lighting where carbon savings are demonstrated.

See: We need ‘sticks and carrots’ and Mike has a grant fund at the NYMNP to help facilitate lighting changes.

With the residential lighting surely this should be aimed at the contractors who are installing it? If it is designed by residential lighting designers control systems would be used which have external lighting on timers or PIR.

MH: All elements of the supply/install chain need educating/influencing. Good design means flexible control and ‘fool proof’ (unable to incorrectly angle) installation. Installers do need to know what the aims are and specifiers need to know what product to select.

JE: All levels of the design and consent process need to have Dark Sky compliance as a core value alongside safe movement, crime prevention, durability/sustainability, etc. The two elements are: the adopted highway road and footway lighting. I’m shocked how often the Section 38 consent process is usually left to the very last item, instead of incorporated into the details of plans, landscaping, etc. earlier on, certainly for larger residential developments. The other aspect is the lighting on the individual properties. Sadly, often the relationship between the two is often overlooked, which can lead to both over lighting certain spaces. Specifically, yes where control systems are incorporated this should be covered. My worry is who takes responsibility of lighting equipment in 5, 10, 20+ years-time, plus the fact that householders can keep adding their own off the shelf poor lighting without any consent process and extremely rarely dealt with via The Clean Neighbourhoods and Environment Act 2005, S.102.

Standards both British road lighting and European workplace standards have requirements for glare control. I see few planning conditions requiring both area performance and glare control to meet the standard. Those examples shown, highlight the importance of glare and upward light that is passing planning control unchecked.

MH: Generally street lighting doesn’t pass through national park planning. It’s dealt with by county. You’re right though that glare from reflection is a key consideration and not just the ULR of the light therefore intensity and mounting height are key considerations.

JE: A very good point. The South Downs NP Technical Advice Note is an excellent example linking the standards to planning decision-making – see Section 7 Lighting Assessments:

How reliable and accurate are SQM’s? Do you recommend any specific brands?

MH: They’re generally considered very reliable but need to be used correctly and in the right conditions otherwise very different readings are returned. We have 10 units and calibrate them against each other to ensure/understand consistency. We use the Unihedron model. We tried an iPhone app as we were hopeful it could be used for citizen science but it returned very random results.

JE: Advice I’ve had is avoid the iPhone apps because of inconsistencies and buy a SQM meter (£120-150 – long wait for manufacture now as must be in such big demand!). We use: Unihedron, but Geoptik are good. SQMs are easy to use with knowledge of moon cycle, weather conditions and allowing the Meter 20mins or so to adapt. Like Mike we use keen volunteers and provide training and guidance.

Has anyone, apart from CPRE, done the satellite data analysis more recently than the 2015/6 data?

MH: Yes. See the VIIRS satellite data at

You can look year by year.

JE: Not UK-wide, although Emma Marrington CPRE’ lead on light pollution & dark skies does want to do an update at some point. A colleague downloaded the VIIRS data to help do that comparison I showed 2103-2020.

Are you able to see the Milky Way being close to or underneath any form of light? If so, do you know a threshold of this?

MH: To get full night vision you need dark conditions for around 20 mins. In dark areas (generally darker than 21.2) this then allows good views of the Milky Way. Even in these areas if you come straight out of a brightly lit building, you won’t see it until your night vision settles. Red lights (often seen at stargazing events) don’t affect your night vision too much. It’s unlikely you’ll get a good view of the Milky Way under any artificial light.

JE: Mike’s covered this well.