I've taken some interest into amateur Astronomy recently and came to realize that, as a hobby, it can get very expensive very very fast. The amount of equipment available at any price range is tremendous and just getting started can mean dishing out some serious money. Learning as much as I could before deciding what kind of equipment to purchase I found astronomers use very dim, red colored flashlights as to allow for their eyesight to remain as adopted to night-time vision as possible. Since every penny worth saving on other equipment equals more aperture for your scope I decided to make a very simple red filter for my, already partly modded (with LED) Maglite.

Time required for this project: 1 hour
Cost: $0 (I had everything on stock a.k.a. rubbish laying around)

Step 1: What You'll Need

To make this you will require at least:
- MAG LITE MINI with an LED instead of the regular light-bulb.,
- A thin layer of acrylic foil. I got mine from a broken ATX power supply. Should be about 0.5mm thick,
- Dark red nail polish... preferably the one your spouse does not like too much,
- Thin magic marker,
- Scissors,
- Fine grain sandpaper

Additionally, I ended up using some duct tape, nail polish thinner and a pair of equally sized plates of glass to press the two chips together.

I would recommend against making this mod with a classic MAGLITE light-bulb installed, as I remember it heating quite a lot as opposed to a bright LED. Than again if you should want do, you could simply change the light-bulb with an already colored red LED and go about it that way.

Step 2: Step 1: Disassembly

Disassemble the top of the MAGLITE. Only remove the very top ring that holds the glass plate in place. There is no need to go any further than that. You should end up with 4 parts as shown below. The ring, reflector ( which is basically useless for a LED mod, but looks better ), the lens and the rest of you MAGLITE.

Step 3: Step 2: Making the New Lens

Now that you've got the original lens, if we can even call it that, out, it's time to take a super thin magic marker and trace the outline of the original lens on the acrylic foil twice. I originally planned on doing only a single side coating, but it turned out horrible as you shall soon seen.

Once you've outlined the shape, cut the new chips out, but make them only very very slightly smaller than drawn as to compensate for the thickness of your marker.

Should you be as clumsy as I am with your scissors, make use of the fine grain sandpaper mentioned earlier to smooth out any irregularities.

You should end up with 3 equally sized ( 1 original + 2 just made ) lenses.

Step 4: Step 3: Painting

Take some double-sided tape and glue your two lenses to a flat surface. I used a small piece of glass I had just laying around. Be sure to glue the whole surface of your plates, not just a center part as I did. I regretted it later when I pressed the plates together and pushed all the nail polish away from the center of the lens making a few lighter areas. So make sure that the whole area of the lens is equally supported.

Additionally ensure the nail polish is thin enough. If you, as I suggested, decided to use a nail polish that is not in regular use it's bound to be half dry. So add some solvent to it to make sure you get a nice equal coating. The picture below is what you are trying to avoid. :) But it will not be a whole lot better in any case especially if your working under a couple of 200W lights like I was.

A word of caution about using aggressive solvents like acetone since it could eat through your new lens depending on the material you've used. Be smart and test your solvent on a piece of foil left over from cutting your lenses.

Paint outwards from the center as to not get paint under the chip, gluing it to the glass.

Step 5: Step 4: Pressing

Once you've added about two coats of paint (depending on the tone of color you've used) it is time to paint both sides one last time and hastily press them together. This will get rid of all the bumps and irregularities you might have gathered during previous applications. Some nail polish will be squeezed out onto the glass. That's exactly why we've used glass.

Press and hold for only a few seconds than hold the still pressed lens towards a light source to make sure the color is nice and evenly spread. If not, twist the two plates around by just a little bit while still gently pressing the plates. That should do the trick unless you made the same mistake as I with not equally supporting the while area of the chips.

Providing the nail polish hasn't gotten squeezed out onto both glass plates you can remove the top one without any damage to your work in about a minute or two. At this point I used a hairdryer on its lowest setting in order to speed up the drying process, moving the lens onto sanding paper in order to make it stop being blown off all the time.

Step 6: Step 5: Testing and Assembly

You can test your work by placing it on a clean plate of glass while balancing the whole thing on a MAGLITE as I did. Overall I was rather pleased with the result, being only slightly aggravated by the white speck I made pressing the plates together two hard.

It's time to put your 4 parts back together exactly the same way it was before except for replacing the original lens with you brand new and dim red filter. I feel that taking a picture of that would simply be an overkill.

Step 7: In Action

Here's the finished product in action at 100% and 30% power. Right of the bat, full power seems like very little light, but given two minutes to adjust, you realize it is still quite possibly too bright, 50% and 30% power are much more suitable in pitch black conditions.

This has been my first instructable. Hope you enjoyed it.

Kind regards, Vince.