Basic Hand Controller
A simple hand controller that provides guiding input to OnStep to help centering objects at the eyepiece can be very useful. While there are lots of ways to center objects; in the case of using a telescope visually many have noted that it's best to NOT have a touch screen (cell-phone or tablet) but rather a control that can be used without ruining you dark adaption. Many OnStep builds, especially those based on my PCB's, include a ST4 port for "guiding". This can be used with a CCD camera to auto-guide or, a hand control can be plugged in and simple push button presses will cause movement in RA/Dec or Alt/Az to take place.
OnStep even supports combinations of button presses to change the rate of movement and control other features (this can be enabled by using #define ST4_HAND_CONTROL_ON in your Config.xxx.h file):
Press and hold [E]+[W] buttons for > 2 seconds...
[E] decreases and [W] increases guide rates (or if tracking isn't on yet adjusts illuminated recticule brightness.)
[S] for Sync (or Accept if in align mode.)
[N] for Tracking on/off.
Press and hold [N]+[S] buttons for > 2 seconds...
[E] selects prior and [W] next user catalog item.
[N] to do a Goto to the catalog item.
[S] for Sound on/off.
(Note: there is an alternate setting for this mode where the focuser's are controlled instead. Press [E] for Focuser1, [W] for Focuser2, [N] to move in, [S] to move out. Add "#define ST4_HAND_CONTROL_FOCUSER_ON" to your configuration file to activate this option.)
The keypad returns to normal operation after 4 seconds of inactivity. If you have the Buzzer enabled you'll get a little audible feedback. A "beep" entering or exiting the special modes and a "click" with selections.
Buying a hand controller
I happen to have a G11 mount and know that Losmandy sells the hand controller for their "digital drive" which works on the same principal. I have an older version of this same HC and it works fine with OnStep. See this page, "Hand Controller for 492 Electronics".
Building a hand controller
A basic schematic can be found in this message. A perfboard implementation diagram is in this message.
Pete Ingram designed and built a very nice hand controller. He also kindly made available detailed information that allows others to take advantage of his work. It helps to have a 3D printer (but one isn't required) and the PCB is available from EasyEDA.
If you have a 3D printer here's the case. If you don't have a 3D printer I suggest looking for a case similar in size and do some careful cutting and drilling.
And the PCB is available at low cost from EasyEDA (link includes the parts list.)
Also, here's a link to some pictures of the project and its construction.
The base of the case has 4 holes for countersunk bolts to hold the two halves of the case together. The top of the box is threaded for M3 bolts. I used these M3 x 25mm countersunk bolts from Amazon.
You will also need an RJ-12 connecting cable. This must be a 6 pole cable a regular phone cable won't work as it only has a 4 wire connection and the project requires 6 wires. I bought mine from Amazon: 6 Pole RJ12 Cable These come in various lengths so you choose.
The slide switches are used to reverse the direction of the motion of the axes. This is useful since some people prefer the motion to be not the true motion of the scope on the sky but the motion of the object in the eyepiece, and there can be all variations of this depending on various optical trains.