My small group of friends will be wearing masks. But could COVID-19 be spread by eyes/eyelashes touching the eyepiece? If so, what precautions should I take?

I have a small Starblast scope with an Orion E-Series 7-21mm Zoom Eyepiece which "consists of six lens elements, which are fully multi-coated with anti-reflection coatings for bright and clear views, rich in contrast." Would 70% alcohol wipes damage the coating? Would it matter if it's isopropyl alcohol or ethanol alcohol?

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    $\begingroup$ About they eyepiece, and it's coatings, you have to consider several things separately. 1) 70% alcohol in water, 2) wipes, 3) wiping, 4) dirt particles getting on the wipe and then causing scratches, 5) water remaining or getting inside the lens, etc. I think the chances of alcohol/water hurting the coatings is probably astronomically low (though no guarantees). Lenses have to be cleaned regularly, typical alcohols that would be found around people can be expected to be grabbed by users. (ethanol, isopropanol, less so methanol). $\endgroup$
    – uhoh
    Commented Nov 7, 2020 at 17:13
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    $\begingroup$ Where I live the local pharmacy sells a liter of 70% ethanol for the equivalent of one or two dollars. Apparently everyone is too scared to drink it. Those coatings are almost certainly hard dielectrics like oxides of rare earths or fluorides, they need to be sputtered coated in special vacuum systems for super-careful control of thickness. About the COVID-19 this is the wrong SE site, people will not give you health and safety advice here, except maybe for "don't look at the Sun!" :-) $\endgroup$
    – uhoh
    Commented Nov 7, 2020 at 17:15
  • $\begingroup$ Not sure if applicable to your telescope: birds4you.nl/de/winkel/… $\endgroup$ Commented Dec 19, 2020 at 9:44

2 Answers 2


After calling Orion (they were nice to answer the phone on a Saturday), they said they can't say anything about using alcohol but they do have an optics cleaning kit to sell.

So I tried to find the ingredient of this cleaning kit, but instead found this, which is from the skyandtelescope web page:

For tougher dirt or stains, various lens-cleaning solutions are available. Good ones are pure isopropyl alcohol or methyl alcohol (methanol), available in drug stores and hardware stores, respectively. Standard, diluted isopropyl rubbing alcohol works well too and is easier to find, but avoid alcohol preparations with other ingredients that may leave stains. Camera shops sell lens-cleaning fluids such as Crystal Clear, which is pure methanol, but you can get methanol much cheaper in a hardware store. Also available are “lens pens” with a soft, retractable, solvent-impregnated cleaning pad.

When cleaning lenses, apply fluid to your cleaning pad, not the lens itself. You don't want any fluid to seep in around the lens's edges; it may carry dissolved gunk to glass surfaces inside and leave stains where you can't reach them.

And this cloudynights web page supports this information:

The cleaning solution I use is 91% pure isopropyl alcohol. A pint bottle is less than two dollars, and is useful to have around the house anyway. Q-Tips are the 100% cotton type. They are used to apply the cleaning solution, and remove the excess.

A word on the alcohol. The 91% pure isopropyl alcohol contains two ingredients on the label, alcohol and purified water. Alcohol evaporate easily at room temperature, and leaves no residue. Purified water will not leave a residue, but will take longer to evaporate. Some rubbing alcohols may contain lanolin or other oils to prevent the alcohol from excessively drying the skin. These should be avoided. Read the label. We want alcohol and water as the only ingredients.

So in conclusion, 90%+ isopropyl alcohol (the other 10% being water) is actually recommended to use on eyepieces after dust is removed and if the alcohol is applied to a cleaning material to wipe on the eyepiece, not directly onto the eyepiece so that it does not seep through the lens. This is wonderful because alcohol kills any virus and bacteria as a bonus!

What I plan to do will be taping a big piece of Saran wrap that covers the eyepiece, and use a new piece each time. It'll be a big hassle, but I don't have enough time to get the 90% or pure isopropyl alcohol now.

Update: The little gathering was a success! I initially had a rubber band to hold the Saran wrap down, but after 2 minutes it got dropped into the grass and couldn't be found. Since I wanted to reduce any wrinkles in the Saran wrap and hold it taut, using tape was not practical, so I ended up using my hands to hold a large sheet of wrap for each family. We saw Jupiter, Saturn, and Mars!

Update #2: This is the response from Orion, and they discourage using alcohol, so be cautious, maybe test it on a tiny spot first with a tiny amount.

Original Inquiry: Can I use alcohol wipes to disinfect the multi coated Orion E Series 7-21mm Zoom eyepiece?

Thank you for contacting Orion Telescopes & Binoculars. We do not recommend using alcohol wipes on any optics , as this could damage the coatings on the lenses. You can on the outside of the lens but not anywhere near the glass lens. We would recommend cleaning fluid for the lens.


Please do not hesitate to contact us if you have any further questions or concerns!

Thank you, Leanne Customer Service Orion Telescopes & Binoculars

  • $\begingroup$ Excellent, well-researched and written answer! $\endgroup$
    – uhoh
    Commented Nov 8, 2020 at 0:13
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    $\begingroup$ You can easily find and buy 99% medical grade isopropanol online. It's not expensive. From that, any water will azeotrope off: en.m.wikipedia.org/wiki/Isopropyl_alcohol#Properties $\endgroup$ Commented Nov 12, 2020 at 15:18

The Celestron video #DearCelestron Series - How to Sanitize your Optics addresses this nicely.

Product Manager John Riutta (responsible for binoculars, spotting scopes, microscopes, and outdoor electronics at Celestron) demonstrates how to clean your binoculars, telescope, and microscopes between users.

In addition to gloves and masks the demonstrate the use of 75% isopropyl alcohol from a drug store or pharmacy and instruct us not to use anything from the liquor cabinet.

I will note however that where I live if you go to the corner drug store and buy a two (US) dollar 1 liter bottle of alcohol, it is 70% Ethanol!

The alcohol is applied to touch surfaces, how to clean eyepieces, especially the glass, is not shown for the binoculars.

For microscopes and telescopes, a 1:48 mixture of bleach to water is mixed and applied with a cotton swab or bud, including to the eyepieces BUT NOT THE GLASS OPTICAL SURFACES THEMSELVES to avoid risk of degradation of the performance.

That's all that's available here.


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