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Does anyone have info on the AccuTrack Omniguide ?

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#1 Nocturnal

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Posted 01 October 2005 - 05:53 PM

Hello,

I have loned a Super C8+ from my astronomy club (SJAA). It's a great scope in excellent condition for being from '85 (or so). Stock the unit has a 110V clock drive which keeps things in the viewfinder quite nicely after polar aligning.

The scope also came with an Accutrack OmniGuide box that has 110 and 12V inputs. It has a 110V outlet to connect to the clock drive and a little 'joystick' on a remote box. Try as I might I can not make the scope move with that joystick. I think I hear a faint change in 'buzz' coming from the clock drive but I don't see it move at all.

Same for the DEC drive. I can see the little motor spin -very- slowly but the little wheel it's connected to with a rubber band isn't even stuck on the DEC axis. Very strange.

So, I Googled and Yahoo'd. No hits. Nada. Does anyone have any info on this unit? I opened it up and the electronics look fine but I'm not really ready to debug the PCB.

Thanks!

Sander

#2 Larry F

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Posted 12 October 2005 - 10:02 PM

I have the Accutrak 4402. If you have the same model, I can send you a copy of the manual, but it isn't very informative about trouble shooting.

First, make sure that the right electrical connections are made. Make sure that whatever motor you are using for the DEC axis drive is properly mounted (see below). Sounds to me like it's not. Also, make sure that the DEC tangent arm bearing is in the middle of the screw, so it has some ability to move in either direction. Then make sure the clutch is tightened on each axis.

For the Super C8, set the tracking rate to SIDEREAL. Then adjust the fine speed knob until the tracking light stops flashing. When you use the hand controller (if it is not damaged) to move the scope in RA, the tracking light will blink. It is registering the difference between the 60 Hz and the output frequency driving the telescope's AC motors. The movement in RA is subtle, since it is intended for astrophotography corrections. It is not going to appreciably slew the tube. You may not see the movement, but if you look through the scope you should see some movement of the stars. When you want to move the tube to the east, it basically slows down the motor a little and allows the scope to fall behind the rotation of the sky, and when you let go of the joystick, it resumes the sidereal rate. It speeds up the motors a little to move the tube west.

The declination motor needs to be attached properly. Here is Orion's instructions [obviously you will have to find the right sockets and Allen wrenches]:

1. Set your C-8 on its side in the carrying case or on a carpeted floor, with the fork arm (with the declination knob) facing up. Remove the two bolts that attach the arm to the drive base, using a socket or crescent wrench.

2. Attach the dec motor bracket with the supplied socket head bolts, using the supplied large allen wrench. "Snug up" but do not tighten the bolts yet.

3. Remove the slow-motion dec know near the motor pulley with the supplied allen wrench.

4. Select the pulley that fits the shaft exposed in step 3. [I assume that the proper pulley is there already]. Slip the drive belt over the motor pulley and the other pulley, and slide the pulley over the shaft. Secure the pulley witht he small allen wrench.

5. Move the bracket as far as possible under the bolt heads to take the slack out of the belt, and tighten the bolts securely. The belt should be a bit loose on the pulleys to avoid binding.

There are no photographs in the manual to help. I had the late Roger Tuthill make a dec motor for my C5. It is not the same as the one Orion made (which I think only fit the C8), and uses a O-ring to drive the dec knob itself, rather than a pulley that would replace the knob. I've included a photo below. Frankly it sounds to me like one of the dec pulleys is not installed or tightened properly, or the clutch is not tight, or the tangent arm has reached one end or the other.

I'd suggest troubleshooting the hand unit by taking a wired female RJ-11 jack (get one from the telephone department at Radio Shack) and simply seeing whether moving the joystick makes resistance changes in appropriate pairs of the wires. That will at least test the joystick potentiometer itself. As for the electrical unit, the only user-servicable part is the fuse, which should be a regular AGC-1A, and NOT a slow-blow.

Hope this helps. Sorry it took me so long to find this post.

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