Calculation of Cloud height

I was asked at Notilucent Clouds Observers’ Forum how I had calculated the height of the clouds I and others observed in the sunset on February 19th 2013.

The calcutions are normally done by triangulation from at least two observing stations. The reason it was possible for me to calculate the height, is due to the lucky circumstances that I observed and noted the time of the sunset, as seen from the clouds. The sunset point gives me the second observing station necessary to calculate the height of the clouds.

On the 19th. I had done a quick and dirty calculation by assuming that the direction to the sun and clouds was due west. Thereby simplifying the calculations a lot. This gave me a cloud height of 57 km which I rounded to approximately 60 km.

Now I have recalculated the height, taking into account that the clouds and sun was not due west but in azimuth 262 degrees. This new calculation gives me a cloud height of 62 km. Which I again will round to approximately 60 km, due to two circumstances which leaves significant uncertainties. First, the observed height (angle) of the clouds above my horisont in Copenhagen known within +/- 1 degree. Second, the exact time of sunset as seen from the clouds is known to happen in the periode 18:18 to 18:23 CET.

You can download my new calculations as pdf-fil here: Calculation of Cloud Height – Clouds observed 19 Feb 2013 from CPH