I have an AO-7 which is a 2001 vintage, used with an ST-8E camera. It has been out of service for a while and I need to bring it back into service. The problem I'm observing is a diagonal oscillation that results in stars being streaked bottom-left-to-top-right in the final image. This doesn't happen when the AO-7 is electrically disconnected. The streaking is perhaps 10 to 20 pixels in length and results in the stars looking like little sausages. I have had similar problems in the past which at the time appeared to be solved by replacing the ribbon cable that connects to the ST-8E camera. However I have replaced the ribbon cable again recently and this time it hasn't worked. I wonder if anyone else has had a similar issue, or whether the phenomenon is something well-known with a simple resolution? Otherwise, what are my options? Best regards, Tim Long
Tim, One of my AO-7 units, time to time, exhibit that diagonal oscillation problem also. Tim, have you solved this problem? I know that you message is from 2016... but nevertheless these AO-7 are still very useful Best Regards, Rui Gonçalves
Doug, I know that. This is a old piece of equipment. But - is this a problem w/ my AO-7 unit or just some wrong settings? Its a transient problem, that seems to decrease w/ faster exposures (higher adq freq.) Thanks for the fast reply, Best, RG
It's probably hardware. It's possible there's an adjustment pot or two inside it somewhere, but I've never looked at the circuitry. I had a quick look but didn't find the design documentation for it. Might have it somewhere, but it's not in our ERP system so I don't even know the part numbers!
Doug, thanks for the info. I'll check at my 2nd AO-7 for those pots (before pull the "faulty unit" from the OTA). Best Regards, RG
Doug, there are 4 pots: XGn, YGn, Xoff and Yoff. Gn must be some kind of gain upon X & Y. Off the zero/central position? Best, RG
Yes sounds like gain and offset. Caveat: if you twiddle these, you're really on your own. See if you can somehow record the initial position, so you know where to go back to. First thing I'd try is just giving each pot a little wiggle, putting it exactly back to the same spot. It's possible the wiper has just gotten bad contact over the years, and that might clean it up. Next thing would be to try and reduce the gain slightly. That said... I don't know which way is up...
Doug, your suggestion seems very reasonable. I'll do/try it next time at the telescope. With care, its possible to open AO-7 back w/o disassemble it from OTA. Very thanks for your support. Best Regards, RG
