Marking Rail Centerlines

Stringing guides from the sides of the observatory and translating that in by the distance marked on the observatory slab gives a 189 inch separation. The actual rail separation is 188.5", so not perfect, but close. Going to try the laser after dark to see if it's one side or the other or just split the difference. A quarter inch isn't going to make much difference one way or another. The biggest problem is that the centerline is even further to the edge of the piers, which is a bit problematic on the down-hill/west side. I'm going to have to either re-drill that center hole or possibly even just remove the existing stud and just use the corners. However, one corner is going to hang over. Sadly, the east side is looking right on center, where there's already the original stud cut off!