OPTEC TCF-S 3" TEMPERATURE COMPENSATING FOCUSER KIT 17677
Item No. 782-20503
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Manuf. No. Optec 17677
Special Order Item
Optec TCF-S 3 inch I.D. Temperature Compensated Focuser Kit, 17677
Mechanically, the TCF-S is a robust Crayford style motorized focuser with high repeatability, no play and nearly zero backlash of only 0.0013 inch. Optecs implementation is ideal for applications which require exact focus such as CCD imaging or film astrophotography. A geared stepper motor rotates the drive shaft with one step rotation of the motor equal to a 0.000086 inch movement of the drawtube. The unit adds 3.5 inches to the telescope's back focus as measured from the front to the end of the drawtube when at the mid-focus position. The total travel of the drawtube is 0.6 inches or 7000 steps. A pair of pushbuttons control the direction of focus and the DRO (digital read-out) displays the current position. The TCF-S focuser can easily handle cameras and instrument packages weighing up to 10 pounds. The TCF-S can be used by itself or with a PC for automatic focus with some of the popular camera control software.
The most important advantage of the TCF-S is its ability to compensate for the focal shift of the telescope due to temperature change. The image plane of the common SCT telescope with aluminum tube can change as much as 0.01 inch per degree Centigrade. This would make long exposures difficult at best.
The TCF-S has a new big brother - the TCF-S3. This 5 pound focuser has all the same features of the TCF-S but is just bigger and stronger. With the every increasing size of CCD cameras and associated instruments, the need for a precision digital focuser that can take the weight and is compatible with most of the camera control software available is now met.
No corners were cut with this model. The massive drawtube has a 3.00-inch I.D. and is made from 7075, the strongest of the commercial aluminum alloys. To prevent any slippage common to Crayford style focusers, the drive rod is pressed onto the drawtube with a force of about 500 pounds. The TCF-S3 can take this extreme pressure because the drive rod is made from a ground bar of high speed steel with a diameter of 0.375 inch. Hardened rails of stainless steel are embeded in the drawtube to engage the drive rod and take the strain.
The total linear travel of the drawtube is 1.00-inch with a resolution of 0.0001-inch. Like the TCF-S, a control box with IN and OUT pushbuttons, serial computer interface and digital display control all functions of the TCF-S3. All other features of the TCF-S3 are similar to the TCF-S. It uses the same cables, temperature probe and the new remote keypad. It is also compatible with the current Optec control software TCF-S.exe.
Other telescope mounts can be made custom in our shop. This focuser is only intended for large scope with massive mounts. See price list for a list of available mounts. A 3-inch to 2-inch adapter is available to fit Optec and other standard 2-inch accessories.