Figuring out the wedge position on the rotary floor


     Lynn baker and mike nolan hung a target under the alfa location and surveyed its position in dome center line coordinates:
lynn's memo:
Mike and I did a survey to start locating the ALFA system on Fri.  We
mounted a single target thru two exisitng holes in the floor.  The target
was horizontally centered between the two holes in the plane of the floor
and extended 22 3/16" below the top surface of the floor.  The floor is
3/4" thick and this is included in the 22 3/16" measurement.  We checked
that the extension was perpendicular to the bottom plane of the floor
within perhaps a 1/4" or so.  We then measured the location of this single
target using the usual technique of surveying a reference set on the
secondary and back fitting a coordinate system in the survey software.
The reference set used is dome centerline coordinates and units of inches.
 We moved the turret position until the y coordinate of the target was
 close to zero.  The turret angle was 26.5 degrees.  The coordinates of the
 target are:
 ALFA4      -246.5803       -0.0677     -393.7084
 For reference, the focal point of the optics in the same system is:
 Nominal focus:   -248.145   .0   -389.822
 The target was not too far from the nominal focus.  Making the
 approximation that the floor is in the x-y plane of the dome C/L system
 with the z axis upward and perpendicular to the floor. (Not too bad for
 small motions).  Moving along the floor 1.5" radially inward from the
 original bolt holes, (away from the secondary) places a point above the
 focal point.  The focal point would be 18.3 inches below the top surface
 of the floor at this new point.

The reference is now the two holes that straddle the center of the pie region. Using:

I get that

The plot shows how i arrived at the numbers.

note 13sep18
There is an error in the plot (found by felix..)


processing: x101/mbeam/