Yes, many kinds of lights can be seen from a distance on a dark night, including a lit cigarette. I could postulate any number of possible signals which might have or could have been used by the Hunley crew, and that is exactly what authors have been doing, without any fact or historical reference. Conjecture and supposition won't cut it with historians when there are primary sources which offer a reasonable explanation. I'll have to stick to the historical facts, science and logic to explain what the "blue light" constituted when observed by the Housatonic's sailor. It was a pyrotechnic signal, not a lantern. The blue light that I've described is much simpler than a lantern, if all you're looking for is simplicity: it doesn't break, it's entirely disposable, doesn't need refilling, burns in all kinds of weather, packs is a small space, is inexpensive, and can be made without any elaborate tools. That's why it was in common use in 1864. If you want the whole research paper on pyrotechnic blue light during the Hunley-Housatonic engagement, it will be published in the inaugural issue of Civil War Navy magazine. Until then, refer to the primary sources in the Wikipedia article on blue light (pyrotechnic signal), and if you find issue with any of the conclusions stated therein, I'd be happy to elaborate in this space.