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Auto-Guiding via an old Meade Autostar-Starfinder?


nightvision
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I have an old Starfinder Eq mount. It doesn't use an ST4 port so no way I can see of auto-guiding it. I wanted to try and use this old mount to autoguide my 300D, it's not striong enough to carry my scopes. The Autostar connection looks like an RJ12 but uses 8 wires not 6 like the ST4 types.

Some pictures showing the internals, looks much more complex than usual non-goto Synta controllers. I can't see any simple way to interface a GPUSB device with this thing. :hello2:

Anyone know if it is possible to interface this controller or the motors with a GPUSB device? The motors take 12-15v power.

Thanks, Tony.

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I believe the GPUSB mod connects to the direction buttons of the hand controller. You should be able to do the same. The contacts of the direction buttons are exposed in your first picture. So I guess this should work the same way.

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I believe the GPUSB mod connects to the direction buttons of the hand controller. You should be able to do the same. The contacts of the direction buttons are exposed in your first picture. So I guess this should work the same way.

I thought that might be the case; I need to look at the way the keys operate, need to establish if they are pressure membranes on the board or if the buttons short-out the printed circuit tracks. Don't have access (as you can see) to the back of the board due to all the chips and it appears to be a complex multi-layer PCB. If I solder on any wires they will need to avoid the buttons.

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the comb-like pattern probably means that the back of the buttons is conducting rubber that just shorts the 2 contacts.

There are 2 contacts per button with an LED in between. If you can't find a way to solder it elsewhere on the PCB, you could compromise and use the left contacts to solder some small wires on and the right contacts for the original button. You would have to press the buttons on their right side when you operate it directly on the hand controller.

Might be a compromise to consider...

Edited by yesyes
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The other option is to carefully remove the solder resist over the track away from the the button contacts and solder to that... if you do you would really want to fix the wire to the PCB with some adhesive as well to stop any chance of it ripping up the tracks...

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Thanks for the ideas, they gave me the confidence to press on. I'll post progress as I go just in case it works.

As suggested the conductive rubber just shorts the print.

The controller has 12v and 5v supplies.

Did some checking and found the common connection for all 4 switches.

All direction switches have no measurable voltage on them so I guess they may be connected to a CMOS chip. I found the 3 top buttons have 5 volts across them and the bottom three have zero volts.

A couple of photos show the layout. I will try to attach some fine wires away from the switch area and post another picture.

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Edited by nightvision
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Good spot on the MC68 CPU, the PCB seems to have at least 3 layers so I wont be using any of the lead-through holes as attachment points.

The tracks are too fine to risk soldering on to them so I willl go for the switch areas which look comparitively robust and already tinned.

Has anyone ever built a GPUSB unit from scratch, or the parallel port version?

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Jolted the memory so I looked back to Rod Mollise 's Autostar files . This link may flag up some information of interest that could save some 'reverse engineering' Weasner's Meade Autostar Information . Somewhere I too have a controller and two axis Meade DS style motors . Been on the project back burner for many years ! Hope the info is of help.

Edited by LeoLion
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  • 4 weeks later...

Made some progress on the guide scope:

Used an old 62mm Spotter scope objective and then a 50mm bino objective as a reducer. Adjusted the position of the reducer until I got an FL of about 270mm for F4.4. It looks bright enough and PHD had no trouble locking on to some dim simulated stars.

Modified the SPC900, just the LE mod, no requirement for amp-off or RAW mode.

Overhauled the mount and removed play, fabricated mounts for the 300D and guide scope. Made everything as rigid is I could.

The guide scope was originally about 175mm FL but figured as it was more than bright enough a longer FL than the camera lenses I have (50mm, 135mm, 200mm) would be better.

Next step will be building the Parallel relay unit to drive the mount controller and a cable hub for the 2 x usb-serial, 1 x usb-parallel, 2 x usb direct connections.

Not having Live-view is challenging when trying to focus so I am working on putting a small video camera on the 300d viewfinder.

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