How accurate are haze measurements made by the VHS-1?
If the EXTRATERRESTRIAL CONSTANT measurement for your VHS-1 is carefully made on a very clear day and if the LED, sunlight hole and sunlight alignment target are all carefully aligned, then the instrument should be able to make measurements which are repeatable to within about 1% for identical sky conditions. For best results, make haze measurements at mid-morning, noon and mid-afternoon. You will probably find that the noon measurements are not quite as repeatable as measurements made earlier and later.
