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Joystickstar

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Joystickstar by Dave Lillis <davelillisa_teircom.net>

This is a simple modification which you can do that allows you to slew/move the LX200 classic using a joystick. The keypad must be plugged into the scope and turned on, its functionality is unmodified, this allows you to use the keypad as normal.

Joystickstar Fig. 1

I wasn't fond of using the buttons on the hand controller for moving the scope, so I found an old joystick that I used on my old Commodore 64 games machine and wondered how hard it would be to attach this to the Keypad, so I could move it north/south/east and west. This joystick uses contacts switches, they are either on or off, many modern joystick would use some kind of varistor or an equivalent, this allows you to do gradual movement in a PC game, but this is not good for our purposes as you need to mimic the buttons on the keypad, if you have one, you can experiment with it to see if it works.

This joystick also has 2 fire buttons, so I used them for selecting the guide speed and slew speed. You can use them for what ever purposes you want, or not at all.

First of all, open up the joystick, you'll see 6 switches in it.

Joystickstar Fig. 2      Joystickstar Fig. 3

In this case they are blue, on each you see 2 pins, when you push the button on the switch, it makes a contact between the 2 pins. You will need a 7 core cable, (is used cat5, 8 cores, one spare) to link the joystick to the keypad. Single out one of these cables, you'll need to solder this to one of the pins on each of the six switches, the order doesn't matter. Then you will need to solder the remaining wires to the second contact of each point.

Joystickstar Fig. 4

You can switch the north and south designations in the joystick, the way I have it here means the scope moves north when it push it forward, Keep in mind that if you select the "reverse order" option in the keypad, you also reverse what the joystick does.

Next is the fun part, you need to open up the keypad using a screwdriver, obviously the scope is turned off and disconnected at this stage. You'll see a circuit board directly in front of you, on the right hand side of it, you'll see a long row of solder points. These points are what join the 20 core cable from the buttons to the circuit board, each one for each button on the keypad and a common wire. So I got my multimeter and pressed the north button and so and found which is the 2 wires were linked by the buttons. By pressing each button in succession, I was able to map out the solder points and find the 7 I was looking for.

Joystickstar Fig. 5

In Fig. 5, I've peeled back the insulating tape here and shown the points. I found to my surprise that there seemed to be a 50ohm resistance in the buttons, so I got a resistor and placed it in the common wire in the joystick. I assumed the resistance was on that side of the switch, if it wasn't, I would need to place a resistor on the far side of each switch, needing 7 resistors, but it seems to work with one.

You can see form the above picture what solder points to attach each of the wires to. You need to be careful and not create any inadvertent shorts, and makes sure the solders are good, you don't want loose wires touching off god knows what inside the keypad. You also don't want the solder points to be "structural", i.e. don't make them the only thing keeping the wire in the keypad or you can be sure they'll break off. I created a small hole in the bottom of the keypad to run the cable out.

I then plugged the scope in and turned it own, it stared up properly and I can now select the speed and direction from the joystick. I presume that you can apply such a technique to the GPS scope, I haven't seen the inside of the AutoStar, but I'm sure the same principle can be applied to it or any GOTO scope. BTW, I'm not going to be responsible for anyone blowing their scope up, do this at your own risk. It worked for me and there doesn't seem to be any side effects, and it makes using the scope even more of a pleasure.

One mod I'm looking into is adding simple switches to the side of the joystick which allow me to control the electronic focuser (1206), obviously I'd need a cable with more cores.

rule

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