How To Clean A Telescope Lens & How Often

Wanting to know about cleaning the optics of your telescope? In this article, I cover how to take care of a telescope, including tips on what not to do so you can get the most enjoyment out of using it.


Ever since Copernicus, Galileo, and other astronomers of the Scientific Revolution started stargazing with their telescopes, and Robert Boyle, Antonie van Leeuwenhoek, and other early microbiologists began peering through their microscopes, care of the optical components has been a critical part of discovery.

Whether the user is looking at tiny bacteria or billions of stars in the heavens above, a properly attuned instrument with a clean and scratch-free lens is advantageous.

All of which naturally begs the question of how to care for a telescope.

How do you take care of a telescope?

Storing your telescope with the dust cap on is a good start to caring for your telescope. The dust cap protects the mirrors or lenses from scratches as well as dust. With regard to how to take care of a telescope, it is a simple task to replace the dust cap or cover after each use.

Your telescope most likely came with this dust cap, so make sure it is securely in place. (But before you do, just make sure there’s no condensation. If there is, allow the telescope to air and dry before putting the dust cap on. Some users believe capping the objectives before bringing the telescope inside works to avoid condensation.)

how to take care of a telescope

So, should you clean the optics, and if so, how do you clean the telescope mirror? How do you clean dust from a telescope? Is it better to DIY or get your telescope professionally serviced? What about storage? Let’s cover these FAQs.

What can mess with your telescope

Before we cover how to clean and care for a telescope, let’s look at what can affect your telescope.

There are a few things that can harm the performance of your telescope. Dust or other fine particles is one. Moisture another. And poor alignment of the mirrors also. Another one not to forget is the mess left from crawling insects and other critters.

  • Dust and pollen
  • Moisture
  • Poor alignment of mirrors
  • Bugs and other pests

Avoiding how much these interrupt the use of your telescope starts with how well you store your telescope.

It’s best to prevent dust or grime from settling on the mirror or lens surfaces and a way to do this is to use dust caps or covers. This way your telescope stays operational with less down-time from dirty optics.

How to avoid a dirty telescope mirror or lens?

Make sure to use the dust caps that come with the telescope and store your telescope in an ideal place, one not likely to suffer from humidity or exposure to the elements. Ideally, you’ll want to keep your telescope in a place where you can quickly and easily observe the night sky because it’s convenient and the telescope is likely to be used more often. But it’s not always practical and may not be the best. The following covers some ideal telescope storage ideas.

Ideally, we’d like to store our telescope where we use it. But this is not always practical.

What’s ideal? Where should I store my telescope?

It’s a good idea to store your telescope inside away from the harsh outdoor elements.

Store your telescope in an area in your home, a closet, shed, garage, or basement. As long as these places don’t suffer from excessive heating or dampness, they will generally be okay. Another problem is crawling critters that can soil your equipment.

See my article on Telescope Storage Ideas to learn more.

How do you store a Dobsonian?

A Dobsonian has its advantages, but it is not the most compact telescope. Unless it has a collapsable tube, it will need a spot with some height or width to accommodate the tube in its rocker mount. It may not fit in your closet.

You can store your Dobsonian in the corner of a room if you have space. If this is a living area, you might find it a great conversation starter, and it won’t be forgotten.

Otherwise, look for a corner space in your garage or basement – just as long as you keep in mind the preventative measures of ventilation to avoid problems from excessive heat and dampness as mentioned above.

How often should you clean the optics?

It might be worth noting that “too much cleaning is worse than too little”, according to Terence Dickinson, editor of SkyNews and author of NightWatch. This is because it increases the chances of scratching a lens.

How to clean a Telescope lens

No matter where you store your telescope and how well you take care of it, your instrument will need some sort of cleaning maintenance at some point in time.

Where there is clogging with visible particles, a dirty lens, for example, you’ll want to clean it to avoid interference and get clear views on the nights you’ve set aside for observing the sky.

Try using a can of compressed air or a camel hair brush to carefully do this. One of the worst outcomes is scratches due to friction. Scratches are near impossible to remove.

There’s the professional means of cleaning and caring for your telescope, but let’s look at the DIY side of telescope care.

DIY cleaning tools 

Options for cleaning the exterior of the telescope lens:

  • a can of compressed air
  • lens cleaner
  • rubbing alcohol (50–70%)
  • soft artist brushes

It’s a good idea to get to know the potential problems before attempting to clean the mirror or lens. One is to never attempt to pull apart the optics to try to clean inside. Another is to not blow on the lens as you may inadvertently add further impurities that dirty the lens.

For the outer part, you can remove the dust from the telescope lens using compressed air. Or if a liquid is needed, gently wipe over the lens with a soft cloth with some lens cleaner or rubbing alcohol, ideally a diluted solution between 50% to 70% alcohol.

Also you can use soft brushes. The best brushes for this process are the very soft artist types (for example, camel hair brushes). With these, you can get rid of most of the dust and other particulates that can collect on the scope.

What to clean and cleaning techniques

Of course, that’s just some very minor dust removal and touch up work. For those still wondering “Yes, but how do you clean a telescope lens?” it’s time to get into that.

Cleaning telescope mirror

Let’s deal with the mirror first. Like the lens itself, this is reasonably delicate, so you don’t want to be too rough with it. What’s more, you shouldn’t strive to overclean here – only do so when it is imperative.

You’ll need to remove the mirror before cleaning it.

Once you are ready to clean the mirror, dilute some mild detergent with some water and swab it gently with a soft leaning surface. Your telescope may come with a soft cleaning fabric, but if it does not, you’ll want something similar and not a paper towel or the like that will be far too rough and scratch the mirror or lens.

You may also need to lubricate certain parts, such as the focuser, to keep it from sticking. Simple Teflon lubricating solutions should be sufficient here. Loosen the screws and remove the part before lubricating it. The same holds true for axes or drives if they start to give you trouble.


Last, but not least, there’s the question of collimating your telescope. This refers to the process by which you align the optics. Adjusting the screws and the arrangement of these help correct alignment issues.

DIY collimation articles:
1. Our step-by-step instructions with diagrams on how to collimate a Dobsonian.
2. How to collimate a Celestron SCT in a few easy steps.

When testing the alignment, start with the magnification on low. In terms of how often should you collimate your telescope, every few months may be a good guideline, but this will really depend on how well your telescope “behaves” and if it’s “temperamental” or relatively stable.

Getting your telescope serviced

Finally, about professional telescope servicing… As with any intricate piece of equipment, eventually things start to wear out or go wrong. While you can fix and refurbish things on your own for some time using DIY steps, eventually professional servicing may be required.

Taking care of a telescope is a process that does not need to be overwhelming. By making a few steps habit, you will be better equipped to view the night sky when you have the opportunity and do so with enjoyment.

In closing

Whether it’s a starter set or an advanced telescope costing thousands of dollars, you don’t want it to become a waste of money simply because you neglected to take care of it and watched it whittle in quality.

Extra info sources

Zlife Education: Telescope Care | Astronomy Magazine: Telescope Care

Nightwatch, a Practical Guide to Viewing the Universe by Terence Dickinson (available at Amazon).

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