This is sort of a follow up to my previous question regarding power supply for my telescope. The general advice I got was that I should just ditch regulation and connect the lead-acid battery directly to the telescope and camera. I have read the manuals for both these devices and both state that is is safe to do so as they both have internal regulators anyway.
However, I almost always connect my telescope to the computer via RS232. My computer does not have a RS232 port, so I'm using a Keyspan USB to RS232 adapter. I don't think the adapter is isolated because I checked with my DVM and there is continuity between the grounds of both (that is the USB and RS232).
The problem is my telescope's electronics are known to be problematic when it comes to ground loops. Some people have outright blown the RS232 chip due to this.
My question is, since the computer is going to be connected to the mains and the telescope + camera to the 12V battery, there is no common ground. Am I going to need an RS232 opto-isolater for the telescope->computer connection?