Hi Geoff,
The image attached is a screen shot of an example of my calculations.
The formula was referenced from the web below.
http://www.physicsforums.com/showthread.php?t=163355
I assumed tungsten for the filament. My major concern was its purity for calculations but figure it is close enough for the purpose of the investigation.
I too thought of the glass and absorption but figure it would be a similar shape for each measurement.
Keep us informed of any developments
