Davidson Optronics Model D638 Coordinate Autocollimator with Built in 
Adjustable Mounting Base.

Heavy duty.  Weight: 22 lbs.


D638 can be used as a two-axis autocollimator since the ocular micrometer
may be rotated through exactly 90deg at either end of its excursion.  It will
read in azimuth or elevation. This instrument has a dark-field reticle and
an illuminated concentric rings. All readouts are taken directly from the
filar readout drums.


Specs:
  • Focal length:                                   508 mm
  • Measurement range:                       20 arc min
  • Accuracy:                                        0.5 arc sec over 1 arc min; 3 arc sec over entire 20 arc min.
  • Sensitivity:                                       0.1 arc second
  • Repeatability :                                 +/- 0.2 arc seconds or better
  • Reticle pattern:                                Dot with illuminated rings
  • Clear aperture:                                60 mm
  • Base adjustment:                            +/- 2 deg. both azimuth and elevation