Product Description
This is a superb example of a ‘top-of-the-line’ Brunson Optical Square, or ‘Jig Transit’. It differs in a couple respects from the current top-of-the-line instrument (the 76-RH). The most obvious difference is in the construction of the cross-axis alignment telescope. It is a ‘straight-shot’ type ocular configuration instead of a right-angle ocular. This does increase the side-to-side aspect ratio of the instrument, but the optical system is more robust and I believe a bit easier and comfortable to use. The other difference is in the design of the base, which in this instrument has a solid azimuth rotation shaft. It does not allow the user to plumb directly to a reference point beneath the transit.
This instrument is fully optioned with all the optional accessories. It includes the type 194 coincidence level on the sighting telescope. Also included is the type 190 micrometer which may be indexed on the front of the objective for line-of-sight deviation readings in azimuth or elevation. More unusual is the type 192 auto-collimation ocular.
Specifications include:
For the main telescope
Objective Aperture = 1.34 inches
Magnification at infinity = 30x
Magnification at 2 inches = 20x
Overall length (with micrometer) = 14 inches
Erect image viewing, 1 degree viewing angle
For the cross telescope
Fixed infinity focal length
Semi-silvered reference window
Erect image
For the 190 micrometer attachment
Plus or minus 0.100 inches, graduated to 0.001 inches, direct reading
May be indexed at 90 degree intervals on the telescope objective
For the 194 coincidence level
Sensitivity to 1 arc second
Simultaneous viewing of both ends of the level – telescope is level when both bubble ends are opposite each other.
Silvered alternating with matte white ambient light reflector
General specifications
Bearing runout less than or equal to 0.000025 inches
Weight approximately 35 pounds
Weight with transport case approximately 54 pounds
The instrument is priced as-shown (without the transport case or illuminators – they were present at one time but have been misplaced in a move – when they are located we will add descriptive photos and the price will be modestly adjusted).
The transit is in spectacular condition – it shows almost no evidence of use. There are a few tiny chips in the finish, but otherwise it looks like it just left the factory. The instrument has been in our collection for a number of years in a display cabinet and will probably require certification before being placed in service.