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Adventures in Eyepiece Cleaning
Submitted: Wednesday, 15th November 2006 by Scott N. Mitchell

Author’s Disclaimer

The author takes no responsibility for any problems that may occur from cleaning your eyepieces as outlined here.  If you are in doubt or have any questions please contact your eyepiece manufacturer or local retail reseller to confirm what will and will not work on your optics.  It is not possible for the author to be absolutely sure about what will or will not affect your eyepieces as there are just too many different types of eyepieces and coatings to test them all.  So proceed at your own risk and please exercise your own common sense.  I am neither an optician nor an eyepiece manufacturer.  I am an amateur astronomer with the emphasis on amateur.  I will set out to describe what I do and what seems to work for me.  I offer no warranty or promise that what I do is right for you and your equipment.

And so it begins

My first eyepiece cleaning journey began when I returned home from one of my first public viewing nights that I attended with a telescope.  While I was putting my eyepieces away I made a horrible and shocking discovery…my eyepieces were dirty!  I was not sure what to do and unfortunately for me, my eyepieces did not come with a set of cleaning instructions. 

I really was at a bit of a loss on how to go about cleaning my precious eyepieces and turned immediately to the internet where I found a whole range of opinions and sometimes conflicting suggestions.  I read everything I could find on the topic and after some consideration and soul searching and armed with imperfect knowledge I decided to dive in and clean my gear. 

An interesting (or not) aside

At this stage I think that it is helpful to the reader for me to offer my opinion on what some believe is a sensitive subject.  Do note that there are two basic types of people when it comes to cleanliness of astronomy gear.  For simplicity sake I will refer to these two people types as the “Felix Type” and the “Oscar Type” after two of my favourite TV characters from the classic TV show ‘The Odd Couple’.  For those of you not familiar with the show, Felix was a high strung neurotic neat freak and Oscar was a much more relaxed and laid back slob of a fellow.  The show in large part revolved around their struggles in living together having been thrown together under an interesting set of circumstances.  For the record, I am much more like Oscar than Felix and I tend to adopt a much more relaxed approach to cleanliness of all things (including Astronomy gear). 

Even after admitting that I am at least in part a slob, I still do believe that having clean eyepieces gives you the best opportunity to have the best views possible and keeping your eyepieces clean in the long term is probably better for their longevity and the longevity of their coatings than not keeping them clean.  So in a nutshell, I try to keep my eyepieces reasonably clean and relatively tidy.   

Optical coatings…are they fragile or not?

Your answer to this simple question will clearly influence how you proceed with cleaning.  I will not debate this question here but simply state my opinion. 

I have stated my experience level with high end optics (more directly my lack of experience) and my tendency toward “Oscar-ness” (some might say slothfulness) so take my opinion with a grain of salt.  I do not believe that eyepiece coatings are particularly fragile.  Eyepieces are meant to be used and they have been built with the idea that they should be able to stand a little wear and tear.  For the record I have even been known to let my sons (age 5 and 9) use my eyepieces and also help in the cleaning process.  Eyepieces and the coatings on them were meant to be used by people not put in a museum display case.

Handled with a little common sense and normal care I believe that eyepieces can handle a lifetime worth of viewing and cleaning.  If you disagree with my opinion on this point then please read no further…

Okay, so now that we have gotten rid of all of the Felix type people us Oscars can get down to cleaning our eyepieces.

First things first

In my opinion there are too many things that can go wrong by cleaning eyepieces in the field.  I believe that eyepieces should only be cleaned in a clean environment that is comfortable and well lit.  While I have watched some people try and “clean in the field” and or clean at night (or in the car etc.) it is not something that I feel comfortable doing.    

That is why when I am going to clean my eyepieces, I set up in one of my wife’s “clean areas” at home…usually at the dining room table.  It is comfortable, well lit and clean and it gives me plenty of room to spread out.  I also find the best time to clean my eyepieces is while my wife is out running errands or otherwise busy outside of the house (what she does not know will not hurt her).

The next thing I do before I begin is to gather all of the stuff I feel I need to do the job properly.  I will once again remind the reader that this is what I actually do on my own eyepieces…it seems to work for me.  Your methods, techniques and equipment choices probably do vary from my own and that is okay with me.  Count on and use your own judgement and commonsense in this task and do no feel obligated to follow my way blindly…after all, I am not an expert.

Remember to be careful in the handling of your eyepieces as you clean them.  There are few things more irritating to me then to put a fingerprint accidentally on a newly cleaned eyepiece lens.  Some people might advocate the use of wearing gloves in the cleaning process but I find that a bit over the top and I think it would introduce more risk of mishandling into the process.  

My cleaning gear

I use the following things to clean my eyepieces:

  • Clean well lit location
  • Hurricane “puffer bulb” (bulb end of a turkey baster or ear syringe)
  • Soft bristled brush (very fine and soft…anti static brush preferred)
  • Q-tip brand cotton bud tupped “ear cleaners” (I use the high quality ones as I don’t want to scratch the lens)
  • Cleaning solution
    • I use the Bintel UHTC Cleaning Solution (available for AUD$10 at The Binocular and Telescope Shop in Sydney and Melbourne, “Bintel”).  There are many opinions about what cleaning products to use and several “secret” recipes to choose from.  I will not go into a debate on this topic as I am not qualified to do so but you can find many opinions on the internet if you look.  The Bintel “blue stuff” works fine for me.

How I clean

In this order here is what I actually do:

  1. I inspect my eyepiece to see how dirty it is…if it looks clean (keep in mind I am an Oscar), I put it away…if it looks dirty I proceed.  I try to only clean things when they need it…call me cautious or lazy (both are accurate)
  2. I gently use the puffer bulb to blow off any dirt and dust
  3. After blowing it with the puffer bulb, I gently brush it with the brush (just to make sure)
  4. I then gently blow off anything the brush leaves behind again with the puffer…I want to make sure that I get any loose dust or dirt off of the lens without scratching the lens.
  5. Inspect the eyepiece again…if it looks clean I put it away…if it looks “oily or smudgy” I proceed
  6. I carefully dip one end of a Q-tip in the Bintel UHTC Cleaning Solution.
    • I try and get the Q-tip moist but not wet…too much liquid is a potentially bad thing and can cause its own set of problems.
  7. Starting from the centre of the lens, I begin to clean the eyepiece with the “moistened” Q-tip using very light pressure in a circular motion.  This will take some practice…too much pressure forces excess liquid out of the Q-tip and creates pools on the lens.  Try to avoid the pooling if you can as they can lead to spots.  I like to gently rotate the Q-tip as I make my way around the lens.  If an eyepiece is really dirty I might use more than one “moistened” Q-tip as I try to keep a one wipe per Q-tip rule in place.
    • Be careful when approaching the edge of the lens with the “moistened” Q-tip as “wicking” of the liquid into the inside of your eyepiece is possible (depending on the eyepiece)…try to avoid getting the inside of your eyepiece wet.
  8. I now use the “dry” end of the Q-tip to soak up any remaining liquid on the eyepiece lens surface.  I again use a circular motion and gently rotate the Q-tip as I go (taking great care so as not to scratch the lens).
  9. Discard the used Q-tip – I am a bit of a stickler on this point…I use a clean Q-tip on each pass and only use a Q-tip once (moist or dry)…(disclosure note:  At this writing I do own stock in Johnson and Johnson the makers of Q-tip brand products)
  10. Inspect the eyepiece while sitting at my well lit work area…hopefully my wife will still be “out.  If it still looks “smudgy” or “oily” I go back to Step #6 and repeat until it looks clean.  Sometimes this takes a few iterations.
    • Occasionally during the inspection I notice what looks like small “water spots” where the “pooled” cleaner dried before I got it picked up with the dry end of the Q-tip.  As a short cut to repeating the cleaning process I will sometimes use my breath to “fog” the lens and then use a clean “dry” Q-tip to dry the lens again using a circular motion and gently rotating the Q-tip to get everything dried up.
  11. I then give the eyepiece another quick “puff” with the blower to make sure that there is no lint left over from the Q-tips
  12. After a careful inspection and when I am satisfied that they are clean and dry, I cap my eyepieces and put them away.

Okay so that is how I go about cleaning my eyepieces.  I am confident that other more experienced amateur astronomers or pickier (Felix type) people will have different methodologies and quickly point out the error and risks of my ways.  They may very well be right and I am open to new ideas and suggestions for improvement.  I again urge you to use your own judgment after all, it is your equipment.

I believe that any cleaning regime needs to have a similar pattern and so in summary here is mine:

  • Inspect
  • Remove dust/dirt
  • Inspect
  • Clean with cleaner
  • Dry
  • Remove dust/lint
  • Inspect
  • Put away


Good luck to you and take heart, if a slob lime me can successfully have clean eyepieces so can you!

Article by Scott N. Mitchell (wavelandscott). Discuss this article on the IceInSpace Forum.

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