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Adding to this ancient thread my interest has gone 180 degrees (angle not temperature) from astro imaging to recording the weather.
I use a WS-1081 system but wasn't terribly satisfied with the external temperature readings which recorded higher than normal temperatures.
My local temperatures seemed to be consistently around 2C higher than the BOM stations in my region during the day.
The radiation shield was the culprit.
The shield is designed to operate under optimum conditions namely cloudy and breezy conditions which maximizes the airflow around the sensor.
While the radiation shield is an off white colour that reflects light in the visible spectrum it still absorbs in the infra red region and heats up.
I decided to design a fan aspirated shield using a plastic container, a plumbing elbow joint and a 40mm fan removed from my obsolete ST-7E CCD camera.
The shield was wrapped in a foil insulation tape that reflects both visible and infra red.
Initial tests were quite promising as comparison temperature testing on two weather stations on my property revealed the redesigned shield gave temperatures that were around 1.0 degrees cooler under sunny conditions.
Unfortunately the ST-7E fan was not a sterling performer and had a flow rate of around 5 cfm.
I ordered a fan with a flow rate of around 12 cfm which provided around a 2C differential over the standard radiation shield as well overcoming thermal inertia faster due to wind changes and rapid variations to solar radiation under partly cloudy conditions.
The fan is powered by an old car battery which is trickle charged with a solar panel.
I'm now fairly satisfied I am getting reasonably accurate readings.
Regards
Steven
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