Quote:
Originally Posted by mithrandir
Up at the farm I got a difference of around .75 between the MW around Crux and the sky to the north west. The best I've seen up there was high 21s (need to get rid of traffic on the New England Hwy), and in the morning it was high 18s in the west between astronomical twilight and nautical twilight. 18.5 is about as good as it gets at home.
SCP would be a poor choice here - that's the direction of maximum skyglow.
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Yes, even relatively faint natural light sources certainly make a difference, so the aim is to find an area in the sky as devoid of light as possible and always try to take readings from that point in order to collect consistent and meaningful figures.
Obstructions are another hazard. Anthony suspected that trees may have been the culprit in the case of the very high readings obtained at the heavily wooded Cherry Springs Park.