Scope electric focusers are all basically the same; a small DC motor driving some sort of connection to the main focuser shaft. The DC motor is then controlled by a low power DC signal from a hand controller connected to it. Simple (Read skywatcher) type electric focusers simply switch output polarity and voltage to control the motor direction and speed. Not the best way, but sure works and it's cheap.
Pulse Width Modulation is the better way, whereby the motor is fed pulses of full-power, just the length of the pulses is used to control the speed. Obviously direction still needs a polarity reversal somewhere in the chain. You can buy el cheapo assembled boards on EBay or from Jaycar etc to do all this, but it gets a bit messy for the neophyte, and still needs USB functionality to be computer-controlled, plus software.
A better solution is to plunk down $130 or so and buy a Shoestring FCUSB box, which has the PWM controller and the USB controller built in, and it's ASCOM ready, plus software specifically designed for electric focusers. No brainer for a simple solution in my opinion. One box is all you need, unless you really want to focus two scopes at the same time, in which case, buy two and go crazy! Read on....I bought one and it's great driving the Meade microfocuser on my C8 (yep, remotely, too).
I've now got my Obs working fine and connected by Ethernet to my house. I love it. So does the better half and the neighbours
Only thing I still have to do is go out to adjust the (manual) skywatcher electric focusers on my Newt and WO scopes, whichever I have on the EQ6 for the night. Well, that sucks
So, this morning, a quick trip to Jaycar, one $1.25 right angle 3.5mm stereo jack later, and I was in business! Cut the RJ plug off one end of the skywatcher handset coiled cord (or you can make up a new one, careful, the plugs are the thin type as used between a phone and the headset, not the RJ11 that plugs into the wall socket)) and carefully soldered the itty bitty wires to the stereo plug tip and sleeve (dunno why they bothered with a
stereo plug, the ring is NC, future use?). Plugged it into the FCUSB and works fine from the obs lappy
I had previously done a pathology examination of the Skywatcher hand controller (curious man), and the RJ output plug was simply the 2 left wires paralleled and the 2 right wires same for the DC, so plenty of choices and no need to worry about polarity either!
Cloudy tonight, so won't get a chance to try it from the luxury of the heated house, but next time will be go out and roll back the obs roof at 5pm (winter), remove lens caps, turn on 12V, insert cameras and come back inside
Remote desktop connection to obs computers, then unpark and do all the rest from inside, taking care not to spill the wine.....then slew and check/adjust focus on suitable star. It's all easy and up to you from then on. Setup imaging, watch TV, process, Go back outside at 11pm, close the roof, etc and go to bed. Ahh, the joys of electronics for the masses
Caveats: Cables, clouds, rain and heavy dew
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