Safe, cheap, and colorful?

[The Lightning Stalker]

For neon, I would use a B7A indicator. Place a 5k resistor in series for 120V operation. They are pretty
cheap. Mercury and sodium require a ballast that usually comes with a special fixture. Sodium lamps will
give you some mercury and sodium lines and maybe a few others.

 

[Cyparagon]

If you're looking for a standard light socket option, you're looking at >$25 for mercury or neon. If you're comfortable wiring mains voltage yourself, neon indicators are <$3. For mercury... if you're okay with the UV hazard (or know how to shield against it), search for "germicidal lamps" as they can be found in variations that fit most fluorescent lamp fixtures.

 

[Ben Goren]

After a bunch of searching, I was able to find a GE 45178 self-ballasted mercury vapor light for $26 at Amazon:

GE 45178 - HSB160/M Mercury Vapor Light Bulb - High Intensity Discharge Bulbs - Amazon.com

I also found this $23 (with standard shipping) medium base neon bulb:

https://www.interlight.biz/light-bulb/R6A

Between the two of those, I should be in good shape...I hope.

(I'm guessing the neon bulb isn't going to be particularly bright, but that's okay. I can use high ISO and / or a long exposure, since I just care about locating where the spectral bands are in the image. And I can merge two exposures, one from the mercury vapor bulb and another from the neon bulb, to get coverage of the entire visible spectrum.)

Again, thanks for all the advise; I'll post an update when I've got something to report....

Cheers,

b&