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AWR Synchronous Motor RA Drive Corrector

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As an old-timer, I still use telescopes with 120 VAC synchronous RA motor drives. As a recently born-again digital astrophotographer, I still need to have a way to control the RA drive. Not long ago, my trusty JMI Mototrak drive corrector gave up the ghost and I was left with only a borrowed Lumicon drive corrector on short term loan. I was aghast and dismayed to find that nobody in the US made synchronous drive correctors anymore! Talk about planned obsolesce! Used models are rarely advertised and when they do show up they are purchased quickly at inflated prices by other astro Luddites.

As far as I could tell the only option on Earth was to buy a custom drive corrector from AWR Technology in England. After some e-mail correspondence with Alan at AWR ( alan@awrtech.co.uk ), I purchased one of their 12V crystal-controlled synchronous drive correctors with the optional variable frequency control and drive corrector port. I am not completely sure how much it cost me with currently conversion and shipping, but it was expensive compared to units like the JMI 10 years ago, part of which is attributable to the woeful state of the dollar. Delivery of the corrector took a while and several e-mail messages, mostly due to my inability to clearly express exactly what I wanted, but eventually it arrived and I got to testing it.

The unit is compact with an extruded aluminum case and a nice paddle unit and tracking CCD port. The CCD tracking port is on the hand paddle, which is perhaps not the way I would build it, but it works. Oddly, the circuit board rattles around a bit inside the housing, and when I opened it up to look at it, that is the way it is built--the circuit board rides in channels in the preformed aluminum extrusion and is not bolted or otherwise captured in place. It has about 1/4 inch to rattle about. This may make it a bit more shock sensitive, I don't know.

I was a bit surprised to find that the third, green ground wire that runs out of the case to the drive motor doesn't connect to anything in the case--that is the metal case is ungrounded. I guess there really is no available ground when powered by a car battery, but the metal case and rattling circuit board makes me a bit nervous, lest I become the ground for 120 volts! The JMI unit was not grounded either, but it was a plastic case, so less of a concern. The wiring of the autoguider port is not the SBIG standard, so I had to make a custom wire, which was bit surprising--I hate making those computer/phone type cables. I also had to install a plug to allow plugging-in the telescope RA drive motor, a minor effort.

Despite these issues, the drive corrector works very well indeed, the drive rate seems quite stable, although there is no frequency monitor as on the Lumicon model, which is not ideal. The unit works with either the 12 volt original relay-type SBIG ST-4 system and more modern "TTL" systems, whatever TTL means. I have both, and it works on both. Response to inputs are snappy and reliable. It looks like this unit will work quite well for guiding my new telescope. Thank God for AWR!

If you order from AWR, go ahead and use their order form--I didn't use it and it resulted in some confusion and delay. Be very specific about the features you want and make sure you are understood--a diagram would probably be best, with all of the details spelled out on the diagram. You may be asked for details that you may not know, like the style of motor you are using, e.g. the size of the start capacitor, if any.

Suggestion--there is likely enough of a trade in these legacy drive correctors to make a nice sideline business for someone in the US for years to come. In the meantime, it is AWR or the s**** heap for those of us who still use synchronous AC motor drives. Note--Alan also says he may be able to repair my JMI unit, so I have a backup.


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