Also posted to a different thread: Old thread but will post here - perhaps will help someone. Error 20 can be triggered by a variety of conditions. One that seldom appears in forums is a battery (control voltage) rather than camera problem. I've been using a DC coupler for astrophotography. Started getting ERR 20 when using coupler only - no problem with good battery. Determined that combo DC coupler and external power supply were delivering about 12V. When external battery was swapped and proper voltage (7-8V) was delivered via same coupler, no problems / no ERR 20. So - check your power source.
