[AstralTraveller (David)]

I have a Celestron GC5 GOTO mount that has become very confused.

The problem started on Saturday night. The pointing had been getting further and further off so I used the 'align' function to replace an alignment star with the DSO in Vela I was observing. I then asked it to go to another object in Vela and wound up in Lupus.

My first though was that the new alignment object was too far from the original alignment star (Pollux) and had confused the calibration program. So I powered off, moved the scope to its start position, powered on, checked that the controller knew the correct time and location and started a two star align. First target star was Acrux, which was near culminating - the scope pointed to low in the south-west. For Spica it pointed about 40 degrees below the horizon in the se. Several more cycles of off and on didn't change anything. So I spent the rest of the night doing it the old way. Tracking and direction arrows both work.

Tonight I set up the head in the lounge room and tried aligning again. Sirius was low in the se, Canopus near the SCP and Regulus below the horizon in the ne. I tried setting the home position (don't know what it does but it sounded hopeful), and then tried returning to the factory default settings and resetting time and location. No change.

The problem isn't a simple offset in RA and/or Dec. It was west of the target for Acrux but east for Sirius. The move from Sirius to Canopus was in the right direction but was too far.

So now I'm also confused. One thought I've just had - does it think it is controlling an alt-az mount? I've put it away now so I can't test that theory tonight.

Any of the famous IIS advice or will be much appreciated.