🚀 go-pugleaf

I don't think you really have to pay $1,500 for an IR scope.

The old Varo Metascope (uses 6929) is being surplused in the
around $400 range.

There's a firm that offering 1st GEN image intensifer tubes
that advertised in the UK Electronics & Wireless World for
a few hundred dollars, various grades, that are ex-mil-surplus.
[These are probably 25mm tubes.]

I believe these require about 2.7KV AC for the voltage multiplier
stages.

The best IR tubes in my opinion is the 6914, used on the M-14
Infrared weaponsight and some tank IR sighting gear.

The Image Intensifier tubes photocathodes usually have a significant
amount of response in the IR region (S-25, S-25ER, S-20), and would
probably operate significantly better than S-1 photocathode tubes
due to their gain. As a matter of fact, the NV goggles worn by
soldiers incorporates an auxilliary illuminator that is an IR emitting
diode. GEN III image intensifier tubes would probably run rings around
the old S-1 photocathode IR tubes (6032, 6929, 6914, etc.) if used in
the IR region.