Location:
The Sky Quality Meter (SQM) was set-up at a location near Leicester Airport, east of the city.
This location was chosen for its flat terrain, free from light pollution. There are no dwelling, street lights, or roads for many miles east of the location.
Set-up:
The SQM was mounted approximately 6 metres from the ground on a telegraph pole, angled at 30° pointing in a North-East direction.
The normal use of the SQM is for it to be pointing vertically to measure light level above for star gazing. As we were interested in the very specific light changes on the eastern horizon the SQM was angled in that direction.
The Azimuth of the Sun changes during the year; closer to North in the summer and closer to East in the summer. The position of the SQM was not changed during the seasons as the north-east direction was adequate to get good readings all year around.
Duration: Automatic data logging of MPAS readings were recorded between September 2017 and December 2018
Data Logging Frequency: A light level reading was taken every 60 seconds from just after sunset to just before sunrise each night during the monitoring duration. The SQM was configured to record a reading when the MPAS was 10 or higher. This level of twilight was achieved a few minutes after sunset until a few minutes before sunrise.
Measurements:
The following was logged at each 60 second reading:
- MPAS reading
- Temperature
In addition the following was added for each 60 second reading:
- Sun Altitude
- Sun Position (Azimuth)
- Moon Degree / Phase
- Moon Illumination Percentage
Aim:
The collection of SQM data was performed with the intention of meeting 2 primary goals:
1. Tipping and Levelling Points
By examining the MPAS reading, establish the first point at which the sky begins to get brighter; the tipping point. Subh al-Sadiq (dawn) cannot occur before this point and occurs at some point after this tipping point as the SQM is more sensitive than the human eye.
The corresponding levelling point for Isha was also established from the MAPS reading; the point at which the sky is not getting any darker and is the latest time Shafaq al-Abyad is achieved as the SQM is more sensitive than the human eye.
2. Changes in Twilight and its relationship with the depression angle of the sun.
It was only the contention of this project that Subh al-Sadiq (dawn) could not be universally applied at the fixed depression angle of 18°, but obviously there must be a relationship between the angle of the sun and the twilight seen above the horizon. The data recorded allowed us to compare the light level at each corresponding depression angle of the sun and determine any relationship.
Observers:
The following attended some or all the naked eye observation dates at the project site at regular intervals between September 2016 to December 2018:
- Maulana Dr Shahid Raza Naeemi (OBE) : Project coordinator / Head Imam - Islamic Centre Leicester
- Yassir Hussain : Project coordinator
- Hafiz Hafeez-ul-Rehman Chisti : Head Imam - Masjid-e-Bilal Leicester
- Syed Sultan Shah Sahab : Head Imam - Gulamane Ahlebait Association Leicester
- Hafiz Ali Raza : Head Imam - Gulzar-e-Medina Leicester
- Hafiz Salim Patel : Head Imam - Faiz-e-Raza Academy Leicester
- Skeikh Sarwar : Trustee - Islamic Centre Leicester