Monitor NTP server

I would like to monitor a public, external stratum-1 NTP server with Orion NPM (or is it SAM that's doing it?)

Curious if anyone has ever done any kind of application or service monitoring, not just ICMP.

The only thing I've tried is adding the node by putting in the hostname, which does resolve to the external IP, and then checking the "External Node". The result is a purple arrow icon but I'm getting no status from it.

Thanks in advance,

Tim