Steve, Why not use a magnetic compass and correct for magnetic declination? The magnetic declination for the location of your sundial can be found here: http://www.magnetic-declination.com/ . Don S
On 9/11/2018 2:38 PM, Steve Lelievre wrote: Hi everyone, How good is a cell phone compass? I mean, if I have no metal nearby and I have the phone set to show True North, what kind of accuracy can I expect if I lay my phone flat and use the compass app? I'm working on a vertical west sundial for a community garden (a.k.a allotment) and have a deadline of end of September to get it installed, because the aim is to unveil it at the group's annual meeting. The dial is to be installed on two posts. I want to get the posts lined up as close to north-south as I can, to make aligning the dial easier. I will use adjustable bolts to fix the dial to the posts, so can I compensate for the line between them being a couple of degrees off - but no more than that. I already have one post installed and concreted in place. I had hoped to use the sun's meridian shadow cast by it to give me a precise line N-S for placing the second post. Unfortunately, rain has set in here and it looks as if there will not be a sunny day for at least a week. I don't think I can wait that long to get the second post installed; otherwise I'll be short of time for the other remaining tasks. Hence my interest in using my phone compass for alignment. Cheers, Steve --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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