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How to Clean a Telescope Eyepiece: Step-by-Step Guide

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Close up of eyepiece of telescope with man's hand. Telescope tuning

There’s nothing more annoying than trying to gather light or magnify an image from a distant object using a telescope that has a dirty eyepiece. Some of us tend to avoid dealing with such an issue, because other than the fact that we lack the experience, we’re also afraid of inadvertently causing harm to the device’s internal components.

We know leaving it as-is would defeat the purpose of using a telescope, and that’s why we must muster up the courage to do it. If you’ve been scouring the internet, desperately looking for a telescope cleaning guide that would make your work easier, you’re at the right place.

But before we go through the cleaning process, let’s first check out the list of items that you’ll need to successfully accomplish the task at hand.shutter camera divider 2

Telescope Eyepiece Cleaning Kit

lens cleaning kit
Photo Credit: Ales Munt, Shutterstock

Telescopes are complex devices. And as such, they need unique items when it comes to cleaning. The good news is, the kit used to clean a telescope eyepiece is not so different from that used to clean a DSLR camera. You’ll find the following items in it:

  • Anti-static brush
  •  Isopropyl alcohol solution
  • Q-tip swabs
  • Distilled water
  • Microfiber cloth
  •  Ivory soap
  • Rubber gloves
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Step-by-Step Guide on How to Clean Your Telescope’s Eyepiece

1. Get Rid of the Excess Dust Using a Bulb-Type Puffer

Mini air blower for cleaning camera
Photo Credit: Sigit dan Flora Fauna, Shutterstock

It’s practically impossible to effectively clean any telescope’s eyepiece without using a cleaning kit. But don’t get that cleaning equipment out, just yet. We first have to get rid of as much dust as we can from the eyepiece’s surface, and the only way to do that is by blowing air into certain areas.

You could accomplish this task using a bulb-type puffer or an ear syringe. We’re okay with whatever option you choose to work with, as long as it gets the work done.

Can you blow off the dust using your mouth? No—you could leave behind droplets of moisture.

And speaking of, removing moisture that has accumulated over time is the other reason why this step is often recommended. Moisture cannot only cause rusting but also facilitate fungal growth.

2. Anti-Static Brush

Carbon fiber anti-static brush
Image Credit: Andrei Kuzmik, Shutterstock

You won’t be able to get rid of all the dust by blowing. But don’t fret, as that’s why we asked you to bring the anti-static brush. Just don’t make the mistake of brushing the telescope’s eyepiece before giving it sufficient time to acclimatize to your room temperature—you’ll easily damage the lens.

An anti-static brush is a special kind of brush made using goat hair, horse hair, or some other low-charging fill material. This type of brush is most useful in situations where the restriction of charges that are greater than 200v is a requisite.

That means the bristles are very soft and proficient at removing dust on coatings and even glasses without scratching the surface. Regardless, you still have to be gentle with the strokes. A telescope’s eyepiece is a fragile component of the system and thus should be treated as such.

3. Take Care of the Grease Streaks Using a Q-Tip

White cotton q-tip in organizer
Image Credit: Olha Kozachenko, Shutterstock

The grease marks are inevitable. They’ll always be there even if you’ve been cleaning the eyepiece frequently. The anti-static brush won’t be useful in this case, but the Q-tip will. Just dab it on some isopropyl alcohol solution and then place it at the center of the lens. Gently rub the surface in a circular motion, while working your way outwards, toward the edges.

Please use the cleaning solution sparingly. If you choose to soak the entire Q-tip into the solution, you’ll have to deal with the residual liquid that will be left on the surface once you’re done cleaning. And that’s more work that could have been avoided.

“Why use isopropyl alcohol solution instead of water?”

It all boils down to the chemical property of water. Grease and oil molecules are normally attracted to the polarity of the isopropyl alcohol solution molecules. But the charge found at the end of water molecules isn’t strong enough to destabilize the chemical structure of grease or oil. 

4. Clean the Excess Isopropyl Alcohol Solution

Q tip with bottle of rubbing alcohol
Image Credit: Wirestock Creators, Shutterstock

Use some dry Q-tips or a lint-free piece of cloth to get rid of the residual liquid if there’s any. We wouldn’t recommend giving the eyepiece time to dry up because once that liquid evaporates it will leave behind oil and all kinds of goop, forcing you to go through the whole cleaning process a second time.

5. Tidy It Up Using the Microfiber Cloth

lens microfiber cloth
Image Credit: byrev, Pixabay

Hold up the eyepiece lens under some bright light. The goal here is to find out whether or not we’ve gotten rid of all the grease marks and dust. If there’s still a shadow left behind, use the microfiber cloth. Gently wipe the surface in a circular motion, and then check again.

If the eyepiece is clean, wash that piece of cloth using a bar of ivory soap. You’ll need distilled water to rinse it and a lint-free space to give it time to dry.

Related Read:

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Things to Avoid

  •  Regularly cleaning an eyepiece even when there’s no grease or dust on it. The only thing that you’d be doing is increasing the chances of inadvertently damaging the lenses.
  • Wiping the surfaces using a heavy hand, especially after applying a cleaning solution. This won’t help you pick up more gunk if that’s what you’re thinking. It will only wear away the lens’ coatings in the long run.
  • Substituting the microfiber cloth with a facial tissue or paper towel. You might successfully get rid of all the dust, but not the lint.
  • Washing the microfiber cloth using tap water. You must use distilled or demineralized water, or the cloth will have mineral deposits once it dries up. In other words, you won’t be able to use it the next time you decide to clean your eyepiece.
  • Directly pouring the cleaning solution onto the surfaces. Dab a Q-tip into the solution instead.
  • Touching the lens surfaces with your bare hands. Wear a glove, to avoid adding more oil onto the lens’ surface or dirt from your skin.
  • Using household cleaners as the prime cleaning solution. It’s risky, as some of them contain additives that could irreversibly damage the lens’s protecting coatings.
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To recap, it’s important to remember to use isopropyl alcohol solution, and not water, while cleaning your telescope’s eyepiece. While water is an incredible cleaning solution, the grease and oil molecules aren’t attracted to its molecule polarity.

Secondly, try to be gentle while wiping the lens surfaces. A heavy hand will certainly damage the protective layers of the lens, thus rendering the telescope useless. Unless, of course, you buy new lenses.

The anti-static brush is the ideal tool for this kind of task, as it doesn’t collect dust. And the microfiber cloth will help you avoid adding more lint to the eyepiece surface. If you’d like to clean the device less frequently, use a dust cap. 

Featured Image Credit: Qvils, Shutterstock

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.