What is the accepted safe way to measure the ripple on a 460 V DC power supplie's output please, using an analogue scope?
And for future reference, on supplies that are in the 3 to 5 kV output voltage range?
Let's put the 5kV case to one side for a while.
Back in the day,before such a specification evinced squeals of terror as seems to be the reaction today,460V DC was just a little higher than the common HT values used on much valve (tube) equipment,& not at all uncommon.
An Oscilloscope which could not,in conjunction with a x10 probe, look at the anode of an Output stage in a high power amplifier would have been regarded as a pretty poor instrument.
That said,there are Analogue 'scopes & analogue 'scopes.
The old 1A5 plugin used in the Tek 545B etc,had a very good voltage offset control,so you could "null out" the DC component & look at the AC ripple at higher sensitivity---from memory,it could have done your job.
One of the plugins in my 7613 has a similar function,but I don't think its range is as good.
If you 'scope doesn't have this facility,you are stuck with "AC coupling".
Most of the time this works OK,but in some cases,there is still too much offset at very low volts/div settings.
In any case,check the specs of your 'scope,& especially your probe.
Tektronix ,HP,or Philips probes normally have quite high ratings,but "El Cheapos" are not as trustworthy.
There is no reason whatsoever to hold the probe when you are testing-------that's what the clip is for!
Connect up the probe,switch your 'scope to a high volts/cm setting,turn on the supply.
If your probe/'scope doesn't show any sign of distress wind up the sensitivity,on AC coupling,( null out the DC first if you have that facility & are on DC coupling)
Read the hum level.
All the above is presupposing that you are looking at the 460V at the output of a transformer type supply,or at the isolated output of a SMPS.
The high DC voltage present after the bridge rectifier in the non-isolated side of a SMPS is a different kettle of fish,as there is the complication of the direct connection of one side to (hopefully) the Mains Neutral.
For the 5kV case,the high value resistor voltage divider idea is the best--just remember that your 'scope & x10 probe look like 10MOhm in parallel with the bottom resistor.
In any case,you are usually interested in hum percentage,so a bit of absolute inaccuracy won't matter.