The Toilet Roll Challenge!
Here’s an interesting Citizen Science project concerning light pollution that I’d like you to help me with… I’m hoping to roll it out more generally as a Citizen Science project over this lock-down period, so I’d appreciate some input to check my calculations. Your location is one for which I have some alternate measurements of sky quality which I can use to calibrate the star count measurements.
All you need to complete the survey is a clear sky and a toilet roll core(!) – instructions are below.
If you can help, I’d appreciate it – submit your results through the web page. If you’ve any questions you can contact me at:

Thank you in advance!

Brian Espey
Light Pollution Researcher
School of Physics, Trinity College Dublin
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• About 11pm (i.e., after the end of astronomical twilight) I’d like you to go outside and make some measurements. (For town or city locations, after 10pm should be ok).

• Go to an area away from direct light, e.g. when you are out for exercise and allow some time to accommodate to the (relative) darkness (you might notice seeing some more fainter stars if conditions are good). If you need glasses for distance vision, don’t forget to use them…

• Using a toilet roll core, point to at least 5 directions (zenith plus another four at approximately 45 degrees altitude, e.g. zenith, N, S, E, W (fill in the intermediate points, i.e. NE, SE, SW, NW if you have time). As a guide, if you’re unsure about where 45 degrees is relative to your horizon (e.g. if it’s obstructed), if you can see the Pole Star, place that just above the field-of-view of the tube, and you’ll be at approximately the correct angle.

• For each position, let your eye roam around the field-of-view and note which stars you definitely see, and which you appear to see most of the time (i.e., are near the limit). If there are clouds in that direction, just skip and move on to the next area.

• Write down the date and time together with a brief note of the conditions (e.g. whether any haze), and provide the star counts against each position.

• The site where you took your measurements needs to be recorded - if you prefer not to be too specific, you can anonymise your location by CSO mapping or provide Google Map Co-ordinates for approximate position.

For More Information see -
1. Date and Time *
2. Your location (check instructions on *
3. Your age group
Clear selection
4. What are the sky conditions (e.g. haze in observed areas)?     *
5. Any direct lights nearby which might influence the observations?: *
Your Total Star Counts: *
Number of Locations recorded: *
Your Star Counts Zenith (Directly Overhead)?: *
Your Star Counts North
Your Star Counts North East
Your Star Counts East
Your Star Counts South East
Your Star Counts South
Your Star Counts South West
Your Star Counts West
Your Star Counts North West
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