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Tingling and slight shocks given by Astro equipment is caused in most of cases by Switch mode power supplies. Almost all of these are “double insulated” having no DC path to the earth and most have 0Volts output (what is generally described as “negative”) connected to the chassis of camera or telescope mount. All of them produce common mode noise that can be measured as voltage ranging from few volts to tens of volts common to both outputs. What it means is that if you measure AC voltage across the output terminals you will read few millivolts. But if you measure Voltage from either output to good earth you may measure anything from couple of Volts to 90 V. This is the reason for tingle you are getting. Your body is providing DC path from the metal chassis of your camera or telescope to the earth. All the measurements I’m referring to are done with digital multimeter with input impedance of 10Mega Ohms. If you try to do same measurement with old analogue meter that had input impedance from 10 to 100 K, the needle will hardly move. The current that passes thru your body during the tingle is less then 1nA.
When you connect two or three PS to power different pieces of your Astor gear that is in electrical contact with each other situation gets even more complicated.
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