NavList:

In my idle moments over the Covid lockdown, I turned my mind to how to make an accurate sun clock by which one might set one's watch to an accuracy of a second or so. After some cogitation, I devised an apparatus which appeared to meet my requirements satisfactorily in that it can be set up to mark local noon to the required accuracy on any day of the year.

However, to ascertain whether an impartial observer would agree with me, I would ask that this group of trained observers each make an independent observation of the moment of "local noon" as determined by this apparatus.

I have made a short movie of the reflections of the sun from the apparatus upon a white board, which you can view at http://www.geoffrey-kolbe.com/docs/sundial_final.mp4

You will see two reflections from the apparatus, one is a vertical red bar and one is a vertical blue bar. The red bar moves to the right and the blue bar moves to the left. At the moment of "local noon", the two bars coincide forming a single bar of white light. The movie starts about half a minute before "local noon" and finishes about half a minute after.

There is a clock above the bars of light by which you might judge when "local noon" occurs. The clock is arbitrarily set so that there is no bias to influence you on when "local noon" occurs.

I would be grateful if you would email me with your estimate (geoffreykolbe at compuserve.com) rather than post it here, so that your estimate is truly unbiased. I will do some statistics on the results and post them here in about one week.

Many thanks to everyone in anticipation.