Product Description
This is one of the industry standard two-axis autocollimators. Manufactured by Davidson Optronics, it is a model D-656. The instrument features a folded optical path so despite the 20” focal length of the objective, the entire collimator is only 12.75” long. The baseplate is very massive, 10.5” by 6” and incorporates both azimuth and elevation adjustments (plus or minus 2 degrees each direction) with super-fine adjustment screws. Instrument weight is over 21 pounds.
Specifications of the instrument include the following:
Accuracy: 0.5 arc seconds over any one arc minute, 3.0 arc seconds cumulative over the entire range of 20 arc minutes
Sensitivity: 0.1 arc second
Repeatability: Plus or minus 0.2 arc seconds
Total measuring range: 20 minutes of arc in elevation and azimuth
Dual Scale Readout: minutes scale and seconds scale at 0.2 seconds/div.
Reticle Pattern: Dot with illuminated concentric rings approximately at five minute intervals. No numbers in the field of view – all readouts are taken directly from the filar readout drums.
Objective Aperture: 2.375”
Reduced Measuring Range at long distances = plus or minus 10 minutes @ 35 feet, and plus or minus 2 minutes @ 135 feet.
Lamp: GE #328 lamp driven by external 115v line voltage regulating transformer
The ability to measure both orthogonal planes with a single dial, and without having to turn the collimator in a precision mounting greatly adds to the convenience (and accuracy) of the instrument. Reference mirrors can be as small as 1/2 inch. The readout dials for the filar ocular are a work of art – the finely divided scale is magnified by the cursor window, and there are fiducial lines one both the crown and underside of the window to eliminate parallax errors while taking readings. Each revolution of the knob directly moves the seconds scale. One revolution equals one minute and this in turn advances the minute drum one division, which is numbered from zero to twenty. For additional information on this instrument please refer to the Davidson Optronics web page at:
http://www.davidsonoptronics.com/D-656.htm
This is a very recent and truly spectacular D-656 and it is in new condition. Original calibration stickers are still affixed. The autocollimator includes a fitted hardwood cabinet which is in superb condition. Also included are the transformer and the light source (not illustrated).
We have a copy of the operation and maintenance manual available upon request.
Location Display 1-2
Photo set 943