STI Autoguider Focusers
STI Autoguider Focusers were developed by Stellar Technologies International to specifically overcome difficulties in focusing the SBIG ST-4, STV, Meade 201XT, Meade LPI, and Meade DSI-C cameras. While parfocal eyepieces have been used to try to achieve proper focus, users have continued to complain about both the difficulty and cost. The STI Autoguider Focusers are best suited for use with separate guidescopes.
How It Works
The STI Autoguider Focuser functions in the same manner as our regular Series IV focuser. All models employ high resolution 180 line/inch ronchi gratings. Simply insert the STI Autoguider Focuser in your guidescope and focus until the image is free of dark bars. Then remove the focuser and insert the autoguider in its place. It is that simple!
Features
* Easy to Use with no calibration necessary. Place the STI Autoguider Focuser in the 1.25" focusing tube of your guide telescope and you're ready to go.
* Elimination of Eye Error is guaranteed. You can be confident the proper backfocus 
of your autoguider is reached each and every time regardless of poor eyesight. No parfocal eyepiece approach can come close to its performance whether your eyesight is 20-20 or not!
* Inexpensive. You do not have to dedicate one of your better eyepieces to focusing, or invest in a high-cost guiding eyepiece just to achieve focus for your autoguider.
* 30 Day Clear-Sky Guarantee to prove to yourself the STI Autoguider Focuser is the best device around for focusing your autoguider camera.
Note: Installing an STI Autoguider Focuser in an existing Series IV 'Stiletto' body requires the use of an adapter ring to interface it properly. These are available in our order section.
Notes -
Users of SCT scopes should not be surprised to see the central obstruction while focusing. This usually appears as a dark circle or as a donut. What you concentrate on during focusing is the lighted area surrounding this circle or partial circle and adjust your focus until the bar pattern appears.
If using a separate guidescope (you should) in conjunction with the Autoguider Focuser, focus normally. When using an extendable tube or helical focuser for focusing the Autoguider Focuser such as OAG, make small changes only between settings. Your eye has an uncanny ability to adjust for images out of focus and you may convince yourself that there is no change in the bar pattern across the image as you focus. When this occurs, simply focus using your electric focuser until you see the bar pattern re-emerge, or better yet, blink in between adjustments. Helical and pull-out type focusers are notorious for tricking the eye in this way. It is for this very reason we do not recommend the use of off-axis guiders with helical or pull-out focusing rings for the critical focusing of anything.
