Edits for some wrong terminology used
No real terminology for it per se, you see/hear it called I2 (Image Intensification). There are differences between Analog units that use photocathodes and Digital units which don't. Specifically a PVS-7/14/31A or DTNVS/DTNVG/Katana are Analog units and something like a SIONYX Aurora is digital.
As far as a "stargazing only" use case goes, you will need to make sure you get a tube with a very low Electronic Background Image (EBI) number (closer to 0.0 is better) and as high of a Signal-to-Noise Ratio (SNR) rating (anything above 30 is pretty good, 35+ is smoking hot).
SNR essentially is how well your given intensifier tube image performs in lowlight conditions - such as an overcast night sky - the lower this number the more "noise" shows up in the image as scintillating artifacts. The higher the number the less scintillation shows up but you will still have a bad image. SNR is still the primary parameter and you should always go as high as you can - most reputable resellers publish the specifications or will make them available to you easily. SNR also lends itself to image quality in your intensifiers in good conditions and this is very noticeable when transition spaces such as an open area, to wooded/shaded areas, to indoors (low-light) areas.
EBI is the ability for an intensifier tube to process images with the lowest possible light hitting the photocathode but in reality that means it will help pickup celestial bodies (from an astronomical use case) and also makes the background image of what you're looking at better. A good analogy to this is setting gamma values in an older video game to help see a bit better and get that dark contrast out the screen.
Temperature, and to a lesser extent high humidity, will artificially increase the EBI of your device so definitely index even heavier on getting a lower number if you are in a hot climate. It's pretty hard to notice differences in EBIs outside of having bino units with a large EBI Variance (e.g., EBI 0.3 and EBI 1.7 - I've seen that personally on a set of PVS-31As) or values above 2.0. An EBI below 1.0 is desirable, I'd say under 0.7 if you live in hot climates, but definitely below 0.4 if you can help it for astronomical use cases.
There is also the distinction between Filmed, Thin-Filmed, and Unfilmed (sometimes called Filmless) terminology. Also, other terminology you will see is White Phosphor (WP) and Green Phosphor (GP). The general consensus is that the best color/contrast and image quality will be Unfilmed WP tubes which are (to my knowledge) only made my L3 now. I will spare you a deep dive in how nightvision image intensification actually works but in short ambient light (photons) hit the photocathode which are turned into electrons and send to the Micro Channel Plate (MCP) before converting to an image you see.
In older designs - and technically this is still true - that electron bombardment was harmful to the MCP over time which degraded performance. The protective Film is essentially a somewhat-effective electron condom. As the chemical composition of films and tubes has changed and technology advanced, it has given way to Unfilmed tubes that L3 is known for, and Thin-Filmed tubes that Elbit Systems of the US is known for. I've lived under NVs for a good portion of my life and can tell the difference between filmed contract (OMNI), thin-filmed Elbit and unfilmed L3.
(As an aside, there is a rumor that L3 is actually still using films but it's just a different technology, anyway I digress)
There are other values such as Gain, Luminance and Halo which are also part of the performance equation, but SNR and EBI are king especially for you folks who would rather look up. That said, the other values will likely be good quality if you have high SNR and EBIs. I'd also lean towards getting those high performance numbers in case you ever decide you want to shoot at night.
Edit: you will also see values around FOM, or Figure of Merit, which is exactly what it sounds like - a qualitative measure of "goodness" with a drastically simplistic quantitative measurement of Line Pairs per Milimeter (Lp/mm) multiplied by SNR. For the most part, every modern tube you see produced from Elbit or L3 will be from 60-82 - usually around the high 60s but Lp/mm is similar to resolution values in thermals.
As far as a recommendation - you'd probably be just fine with a set of PVS-14s, it's a single monocle and very well supported in the market. If you want the Rolls Royce so to speak look into a unit with L3 intensifer tubes, they grade them based on set of minimums per category. L3 goes with 18-20-22-24UA/UM so the higher number means you at least won't dip below specs. Does that mean you cannot get some mind-blowing good with a 18UA tube? Nope. That said, I've used a lot of Elbit XLSH thin-filmed and their "aviation grade" tubes (SLH or YLH, I forget what they call it) and they can get high performance too.
I'd give a call to folks from either: Kosher Surplus, Steele Industries, Apollo Gear Company, Goonin Gear LLC or Licentia Arms Company as they're all very consumer-focused shops to chat them up if you have any doubts (not saying other shops arent good). They all publish specifications with their units they have on hand and will also build you a unit off of a hand-select. PVS-14s will be easier to build since it's just one tube and easy-to-get housings + glass and you don't need to pair it. No tube is created equally.
Longer answer to your question - hope that helps.
