A 1.875-inch Diameter Counterweight Shaft (M12601-E) is 22-inches of extension.
Note: This Current Style 1.875-inch Diameter Shaft Requires a One-Piece Safety Stop for 900, 1100, 1200, 1600, and Mach1GTO Mounts using 5, 10, 18, 24, and 30 pound Counterweights.
This style counterweight shaft with its one-piece washerless safety stop ships with the 1100GTO and 1600GTO mounts, and began shipping with 1200GTO mounts in May, 2006 and continued with the 900GTO's that began shipping in January, 2007. An optional shaft was also introduced for the Mach1GTO at the beginning of 2007. By machining the same size threads at all connection points, the various pieces work together as a system and provide an enhanced level of convenience and versatility to your 900, 1100, 1200, 1600, or Mach1GTO mount.
Image of the 1.875-Inch Diameter counterweight Shafts Series and the One-Piece Safety Stop.
The one-piece, machined, aluminum, washerless safety stop (shown above) is easier to use than the older knob and washer, especially in the dark, and you don't have a washer to drop and / or lose. A newly added Delrin washer (F0020) (shown right) helps prevent the counterweight shaft from seizing against the mount's CW shaft adapter. The extension eliminates the need for a separate longer shaft for mount owners with heavier equipment loads.
PLEASE NOTE: Very Important:
Do not use the counterweight shaft without the safety stop!
The current safety stop and extension cannot be used with older style shafts. The older style knob and washer cannot be used with the current shaft and extension.
The current counterweight shaft, safety stop and extension may not work on mounts to which the mounted encoders of digital setting circles have been installed. See the detail on each shaft for specifics, and if in doubt, check with OPT Technical staff before purchasing. 900GTO mounts after serial number 900451 cannot be used with shaft encoders anyway because of a design change to the RA axis.
These components are compatible with the Astro-Physics' 5-pound (5SCWT), 10-pound (10SCWT), 18-pound (18SCWT), 24-pound (24SCWT), and 30-pound (30SCWT188) counterweights. They cannot be used with the 6-pound (6SLCWT) and 9-poud (9SLCWT) counterweights.
Image Above: Compare the differences of the Shaft ends for proper identification.