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Summary: /* What you’ll need */ A red “night vision” flashlight is essential for astronomy. If you need to read a map, check a star chart, or fiddle with your telescope or camera, you can’t use a regular flashlight. For optimal star-watching, you have to let your eyes adjust to the dark of night. This takes a few minutes, and any bright, white light resets the process, ruining your night vision. But if you use a red light specially-made for astronomy, you can still read, fiddle and find your way without upsetting your own night vision or that of the people around you. Night vision flashlights can be purchased wherever telescopes, astronomy supplies, or camping gear is sold. Most fancy camera stores have them, too. But here’s the DIY version! ==What you’ll need== * A small flashlight – use the kind with an old-school bulb, not a CF bulb or an LED array. * Red “Holiday” plastic wrap – the kind you use in the kitchen to wrap food. Major manufacturers usually brand these tinted rolls as “Holiday” wrap. The red can be difficult to find outside the winter holidays, but they are available year-round online and in well-stocked grocery stores. You can also use red gels (used in theater lighting) if you can find them. * Rubber bands * Scotch tape ==How to proceed== ”’Tear”’ off a piece of plastic wrap wide enough to fit over the business end of your flashlight with an inch or two to spare on either side. ”’Fold”’ the red plastic wrap end-over-end, making tidy squares. Continue folding (and adding more strips of plastic wrap, if necessary) until you have a square about 1/8 of an inch thick. ”’Secure it”’ to your flashlight using rubber bands and/or tape. ”’Test it”’ to make sure there are no white light leaks, and that the thickness is sufficient to preserve your night vision. ”’Do it”’ again. Make a few of these 1/8 inch thick filters and stash them. You can hand them out, or replace yours if it becomes damaged in the field. [[Category:DIY]] [[Category:Astronomy]]