Used Optec Temperature Compensating Focuser-TCF-S

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  • Regular price $749.00

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  • This is a used focuser in very good condition


Used Optec Temperature Compensating Focuser-TCF-S

The Temperature Compensating Focuser by Optec: the TCF-S is a robust Crayford style motorized focuser with high repeatability.

"One of the single greatest detriments to taking truly outstanding astronomical images is the focus shift due to changing thermal conditions. A small change in ambient temperature can cause otherwise sharp stellar images to bloat in size, ruining the final image and wasting precious observing time. Someone needs to develop a focusing system which compensates for these temperature changes and holds the focus steady throughout the night."

Optec has developed such a system. The Crayford design allows for a solid friction roller focusing system with no play and very little backlash. Optec's 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 0.00008-inch movement of the drawtube. A pair of push-buttons 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.

Unique to the TCF-S focuser, an electronic controller system monitors the telescope's tube temperature and compensates the focus accordingly. A small temperature probe is attached to the side of the telescope tube and monitors temperature with a resolution of 0.1-degree C. For a typical Schmidt-Cassegrain of 8 to 11-inches aperture and f/10 focal ratio, the back focus will move approximately 0.010-inches for every 1-degree C change in telescope temperature. It is not unusual during an observing session for the ambient temperature to change by as much as 10-degree C within the time span of a few hours. This change in focus due to temperature is a serious problem for most telescope designs and requires frequent re-focusing during long exposures. A typical RGB exposure sequence can last one hour making it imperative that the focus be checked and corrected after each filter change.

A simple learning procedure is used to find the temperature coefficients specific to the user's telescope system. The TCF-S system allows for two different coefficients (corresponding to two different f-ratio configurations) to be calculated and stored in the EPROM memory. Once learned, either coefficient can be selected with a simple slide switch. A manual mode allows the user to set the focus manually at any time.

The digital nature of the TCF-S allows opportunities for truly intelligent focusing. With the serial version TCF-S focuser, programmers can communication directly with the focuser's controller (located in the hand control) via any serial port. The simple ASCII protocol is easily programmed and has been implemented in many popular imaging and camera control software packages. MaxIm DL/CCD version 3 now provides remote and automatic focus control with the TCF-S focuser.

At the end of an observing session, the TCF-S focuser remembers the last temperature and position. When the unit is turned back on for a new session, the TCF-S computes a new position using the current tube temperature and moves to that position. Assuming no changes to the optical configuration, the object will snap into sharp focus.

Advantages and Capabilities of the TCF-S Focuser

  • Solid, heavy-duty Crayford-style 2-inch Focuser.
  • Automatically compensates for focal shift due to temperature changes.
  • Capable of supporting instrument packages up to 10 pounds.
  • Easy to use hand controller with push-button focus control.
  • Built-In 4-digit DRO (Digital Read Out) display.
  • Simple Learn procedure for determining temperature coefficients.
  • Shut-off procedure stores and remembers last position.
  • MaxIm DL/CCD Version 3.0 compatibility with TCF-S.

Below you'll find a list of explanations regarding important accessories that may be required for this product. To add them to your order, just click on the "Accessories" tab and choose the appropriate items.

  • If you wish to control the TCF-S via its hand controller at any time, an Optec RJ-45 to DB-9 cable that connects the two is necessary. You can find different lengths of control cable in the "Accessories" tab.
  • The Paramount ME Mounting & Wiring Kit is a specially designed mounting platform and hardware kit for mounting the IFW and TCF-S hand controllers to the telescope plate of Software Bisque's Paramount ME. Includes all hardware, tools, and wires needed to take advantage of the internal auxiliary ports of the mount. The IFW and TCF-S hand controls are placed at the telescope with minimal wiring clutter.
  • The PC Serial Port Converter allows PC serial communications with the TCF-S Focuser and IFW Filter Wheel using any 9-pin serial port. If you purchase the PC Serial Port Converter, an RJ-12 Reverse Cable is also required for proper operation.
  • In order to attach the ITCF-S to your telescope, you'll need mounting hardware. There are mount adapters available for several makes and models.
  • Finally, the TCF-S is a 2-inch focuser. You may need a T-thread, SCT, or 2-inch to 1.25-inch Adapter. You can find them in our Accessories tab.


ConditionVery good
Warranty90 Day Covered By OPT


  • Optec TCF-S focuser
  • Manual control box
  • 3" Meade thread adapter
  • AC adapter
  • Temperature probe


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