Today I just Kentucky Windaged the sensor to make it level.
I'm not at all sure what that means in context of a weather station, or whose sights are being aimed and at what; could you describe what you're referring to?
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In addition to everything the George points out in regards to siting, micro climates (great related read
here), and compromises, the bulls eye level bubble on the Osprey is indeed something to be concerned about; moreover, in making certain that the outdoor array is level because it influences the tipping bucket's performance. And how significant that influence is, may be surprising.
When I placed the Osprey on its super plumb mast on the day after Christmas 2018, I thought the assembly had to be super level. Note that vertical lines are plumb, horizontal lines are level, despite how often these terms are misused! The next day, I hoisted my camera aloft and discovered the bubble was barely contained within the red circle of the bulls eye. I thought at the time: close enough, while harboring uncertainty.
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Thanks to that uncertainty, I purchased a Stratus rain gauge. Eventually the frozen ground thawed, and the thing was set in place just in time for a rain event. Then looking at the first returning numbers (see
Buckets and Tubes spreadsheet for details), it seemed like this was a time for spring cleaning and re-leveling.
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While the differences between Osprey's reported rain and the readings from the Stratus rain gauge improved, they still were greater than me and my nerdy OCD would have liked. During a break in our rainy weather, I lowered the mast again to try and understand some of the issues at play. My conclusions were that 1.) even though the top of the mast was squarely cut and super level, the muffler clamp style connector introduces asymmetrical force when tightening, and 2.) the Osprey is nose heavy with its center of gravity north of the connection. This is also the axial direction (S-N) in which the rain bucket tips.
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After about 5 hours of messing around, I found that torquing the upper u-bolt first and with greater torque than the lower u-bolt on the muffler clamp assembly mitigated some of the northerly roll downward. I don't have enough data since my last re-leveling, but early returns and differences of 5% to 6% give rise to wondering about how closely the bulls eye level and the tipping bucket are aligned to each other. Fortunately so far, there's been only light to moderate winds during rain events, and lessening the differences between the two devices caused by overcatch.
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