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:

8.17 degrees for the tilt angle of the horn
18.3 inches focus below the top of the floor (measured by lynn and mike)
1.5 inches radially in to go from reference to focus
24.4094 inches alfa focus to where alfa attaches to the wedge
4.5 inches as the vertical height of the wedge at it's center
1.063 inches radially inward as german corte's offset (in the tilted focal plane).

I get that

the center of the wedge should be 5.82 inches radially inward from the holes on the floor.
We need a shim of 1.22 inches between alfa and the wedge.

processing: x101/mbeam/wedge.pro

 home_~phil