The Prima Luce Lab Sesto Senso is the robotic focusing motor designed to be connected to the shaft of your focuser by removing the coarse and fine knobs (it requires your focuser to have micrometrical knob) - without the need of external and uncomfortable brackets thanks to its Self Centering Clamp (SCC).
Most of the focusers in the market have 25mm diameter shaft and Sesto Senso will connect out of the box. Other focusers may come with 26, 33 or 37mm diameter shafts: in this case we have the optional 26, 33 or 37mm adapters for the Sesto Senso.
In this article we'll see how to install Sesto Senso robotic focusing motor on different telescope focusers, as well as those which require the additional adapters.
In order to connect the Sesto Senso to the focuser of your telescope, first remove the manual focus micrometric knob by unscrewing the screw normally present on the knurled knob. After removing this, you will also need to disconnect the coarse focuser knob, by means of an allen screw on the knob.
On some plastic-covered focusers, you need to remove the plastic to access the disassembly screw. Connect one of the bushings found in the Sesto Senso box (based on the diameter that fits your focuser) to the small focuser shaft of your focuser.
Now you can connect the Sesto Senso to your focuser by paying attention to centering the micrometric pin with the pre-assembled bushing on the Sesto Senso until it stops. By using the provided allen key, lock the 2 grub screws that fix the pre-assembled bushing on the Sesto Senso to the bushing you just installed on your focuser's shaft.
Connecting the Sesto Senso body to your focuser.
Use the allen key to evenly fix the 3 small grub screws to secure the Sesto Senso in position.
Lock the 3 small grub screws evenly on to the outer ring of the Sesto Senso.
Finally, using the provided allen key, tighten the large screw that fixes the Self Centering Clamp of the Sesto Senso to your focuser (making sure not to overtighten!).
Tighten the large screw that fixes the outer ring of the Sesto Senso to your focuser.
NOTE: Make sure you do not overtighten the large screw! If it is too tight, it will exert an uneven clamping force to the bushing on the focuser shaft, deforming the bushing. This will result in slipping of the Sesto Senso's motor.
After installing the Sesto Senso to your focuser, check the smoothness of the movement by keeping the Sesto Senso powered off and then manually moving the focus knob of your focuser. The presence of the Sesto Senso will make the movement harder (since the motor is connected) but the motion must still be uniform. If you notice an uneven movement, repeat the installation procedure.
For focusers with different diameters:
If your focuser has a different diameter, you can add the 26mm (SESTOSENSO-AD26II), 33mm (SESTOSENSO-AD33II) or 37mm (SESTOSENSO-AD37II) adapters. Shafts with other diameters are not compatible. Please note that these adapters are compatible only with the Sesto Senso 2 and not with the first generation Sesto Senso.
In order to install the adapter, first connect the long bushing (the one that comes in the adapter box) to your focuser’s shaft (making sure to leave a small gap between the end of the shaft and the bushing) and lock it by using the 2 grub screws. Please note, it’s normal that the other side of the bushing has no threaded holes.
Connect the long bushing to your focuser’s shaft, making sure to leave a small gap between the end of the shaft and the bushing.
Then take the red adapter and connect it to your focuser by fixing it with the provided screws.
You will then be able to connect the Sesto Senso 2's main body. First, fix the grub screws that connect the internal flexible shaft of the Sesto Senso 2 to the long black shaft. Then fix the screws that connect the Sesto Senso 2's 25mm Self Centering Clamp to the adapter.
Connect the Sesto Senso body to the red adapter.
Note: The Sesto Senso connects to several focusers that may have different machining and tolerance precision. Focusing accuracy, especially when using automatic focusing procedures, depends on the focuser mechanics and not only strictly on the Sesto Senso. If your focuser has significant backlash, you can adjust the backlash parameter in the software.