Celestron Power Supply

I bought a Celestron Power Supply #18773 for my Nexstar 8 Scope.
It says it puts out 12V 1.5A. Since it was used I thought it best
to hook it to my voltmeter and be sure it works ok. Without a load
it read 15.4 volts. Is that normal in order to compensate for the voltage
drop when under a load?

Pretty typical really, 13.8v + for most.

Although I don't have a Celestron labeled power supply, all the other 120vac > 12vdc power supplies I own put out around 14~15 no-load volts. That's about normal.