If it is an exposed rated lamp, then I would say yes this is probably safe.

But assuming it is an enclosed rated lamp (as most are), then I would say maybe. If the lamp is used (or you don't know it's history), I would not at all run it in the open. Technically even a brand new lamp can explode with a severe enough manufacturing defect, but I haven't seen that.

Explosion is always a risk, but if you shield the lamp or shield yourself you should be relatively safe even with an old lamp.

Running them vertically reduces the likelihood.

I recently purchased some 400watt MH gear and would like to know if it’s safe to run the lamp out of an enclosure. I do know that MH lamps have the tendency to sometimes explode apon EOL.

There's a light in English class that looks close to EOL and it's really mercury starved and the other lamp on its ballast is a little dim too even though it looks new.  In fact that entire room is basically just one big EOL lol though it's actually more EOL ballasts than lamps

https://www.lighting-gallery.net/gallery/displayimage.php?album=9185&pos=0&pid=267212

Yes, use the wet sponge on cold tip is generally ineffective, but some people still do it, as a "last try to clean the tip before it cools down completely". And on top of that using rather large forces to scrub it off. Not realizing they are just damaging the things (both the sponge by tearing it apart by the force and hardened solder spikes on the tip, as well as the tip corrosion afterwards).

And for the shocks: It is not immediate destruction, just the surfaces wearing out over time by fatigue cracking within the coatings. 300..350 is still somewhat within the limits, for lead free you sometimes need to go up to 400degC (if you need small tip to melt the solder very quickly) and there the shocks become really way greater. Yes, it is not good practice to use that high temperatures for long time either, but that is another topic, sometimes you just need it.
But it is matter of how long the tip will last, not that much whether it survives short term or not, of course it does.

Here is an example of Chinese cheated with the use of low resolution spectral sensor. Not many users today with discharge sources, and this is not very much noticeable with smooth spectrum LEDs.

I suggest to return this meter while still possible. Or sell it to someone who could use it for its intended purpose, measuring light levels with some added benefits of flicker or *rough* spectral balance.

@Medved Any practical examples where cleaning the tip with wet sponge have done *any* harm due to a thermal shock? Or you are just theorizing?

I am doing it all the time for many years since modern soldering tools has become available, with tip temperatures of 320-350C, also it is a standard practice for the industry, no one uses brass shavings seriously, as it is less convenient. More, most soldering stations come with soldering iron stands having wet sponge plate embedded.

Also, there is no point to use a sponge (or be it brass shavings) on a tip with a temperature below water boiling point as the solder will obviously be solid too, and all sorts of cleaning (short of a file or a sandpaper will be ineffective!
 

@dor123 , have you tried the spectrometer with single wavelength light sources? See if the reading on the spectrometer matches with the actual wavelength. For example, a red laser is ~650nm, a green laser is ~532nm, a violet laser is ~405nm, a neon lamp has a peak at 632.8nm. If the values for these are close (+ or - a few nm) then the spectrometer should be correct.
(Don't point the laser directly on the spectrometer, point the lasers on a white wall and place the spectrometer pointed towards the wall looking at the laser dot.)

There is no calibration instructions in the manual.
"Note: The calibration function is restricted to use by metrology institutes only and is prohibited for use by
non-professionals."

If im not wrong, your spectrometer is model LS335. If its of any help, try downloading the manual for it here.