For many people that are into stargazing, the choice of supplies and methodology to clean a telescope’s mirror is a topic almost as controversial as their political views. Everyone thinks they know “the right way” and “the best trick”.
One of the most common subjects of this discussion is good old Windex. So let’s settle this debate once and for all.
Can you use Windex to clean a telescope mirror or lens?
Yes. It is safe to use Windex to clean telescope optics as long as it is the original blue glass or invisible glass formula. Using the right cleaning method is more important than the liquid you decide to use with a few exceptions you should avoid.
Windex has been tested widely on telescope mirrors and lenses and it does not leave a film. Some people used to be against its use because it contains dyes and a fragrance which are usually a no-no for lenses, but the quantities are negligible and the formulas have proven to be safe to use.
Even one of the best optics companies in the world, Televue, has chimed in on the subject and assures us that Windex is ok and that you should care more about perfecting the cleaning method.
Here’s the complete list of ingredients in Windex:
- Ammonium hydroxide
- Lauryl dimethyl amine oxide
- Sodium dodecylbenzene sulfonate
- benzyl acetate, butylphenyl methylpropional
- Liquitint® Sky Blue Dye
Substances to avoid while cleaning a telescope
While Windex is ok to use. There are some other liquids and substances you need to be careful about using on your expensive telescope mirrors and lenses. The following items are not recommended.
- Acetone – While acetone is a good cleaner for grease spots and is safe to use in terms of residue, it can cause a flash fire, making it a hazard, specially if kids will be using it.
- Nail polish remover
- Cleaning liquids with perfume
- Paper towels
- Cloth (maybe except for microfiber, but even then tissues are a better choice)
- Canned air
How To Clean A Telescope Mirror With Windex
- Use an air puffer to blow any dust off the mirror. Do not blow into the mirror as you don’t want to spit all over it. Some people also “vacuum” the dust by sucking air with their mouths but then all the dust goes into your lungs. We recommend the puffer.
- Slightly moisten a tissue or q-tip with Windex. Tissue for the bigger lenses, q-tip for the smaller ones like the ones in eyepieces and diagonals. Do not soak them, just spray a little bit.
- Gently blot the surface with the tissue. Don’t wipe or rub yet. Just softly “tap” the mirror.
- Blow off the dust again.
- On a separate tissue/q-tip, apply some more Windex or alcohol. Again, don’t soak, spray it if possible.
- Starting from the center, wipe the lens in circles from the center to the edge. Go very slowly so you wipe the liquid from the previous circle as it drips down. Use multiple tissues if necessary.
- Finish the corners with a q-tip or a folded tissue to wipe around the edge, again, in a circular motion.
- If there are spots left. Fog the surface of the mirror with your breath and wipe just that area with a new tissue sprayed with your cleaning liquid (alcohol, windex or whatever you are using).
- It’s ok to use Windex to clean a telescope mirror or lens
- The cleaning method is more important than the cleaning fluid
- Always apply the liquid to a tissue, not directly to the lens.