Figuring out the wedge position on the rotatary floor
Lynn baker and mike nolan hung a target under
the alfa location and surveyed its position in dome center line coordinates:
Mike and I did a survey to start locating the ALFA system on Fri.
mounted a single target thru two exisitng holes in the floor. The
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
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
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
close to zero. The turret angle was 26.5 degrees. The
coordinates of the
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
with the z axis upward and perpendicular to the floor. (Not too bad
small motions). Moving along the floor 1.5" radially inward
original bolt holes, (away from the secondary) places a point above
focal point. The focal point would be 18.3 inches below the
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
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
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.
The plot shows
how i arrived at the numbers.