ASO fine optics CLEANING SYSTEM: Part I 
PRECISION COATED OPTICAL Lenses, Corrector Plates 
and other REFRACTIVE GLASS 
by 
Dr. P. Clay Sherrod 
Arkansas Sky Observatory 
______________________________________________________________________________
  
PREFACE: 
There are many, many variations of high precision, high reflectivity and high 
transmission coatings presently offered on the market for both amateur and 
professional scientists who use OPTICS in their respective lines of study. 
Smaller glass surfaces with high transmission coatings have always been 
seemingly easy to clean, since the smaller surface area is not as prone to 
spotting, sleeking and streaking of the cleaner used.  On the other hand, 
large optical surfaces such as telescope lenses, corrector plates and optical 
glass "windows" are very difficult to properly clean without some residue 
being left behind as a result of cleaning. 

The ARKANSAS SKY OBSERVATORY's new protocol for cleaning optical surfaces 
includes: 
1) judging carefully when cleaning is actually necessary 
2) preparation of the optical surface for proper cleaning 
3) a new solution that combines the attributes of all previous formulae and 
results in very fast, easy, and streak-free results if used properly 
4) the proper new technique that is highly recommended for cleaning. 

WHEN TO CLEAN OPTICS: 
Although we are attempting to obtain the best possible light transmission 
efficiency from our optics by cleaning them free of deposits, film and debris, 
lock firmly in your memory that cleaning coated optical surfaces is the 
single-most damaging action that will be done to them, short of actual physical 
damage or breakage.  No matter how careful, how delicate, nor what cleaning 
solution is used.....every time cleaned will result in a microscopically-reduced 
optical performance than before cleaning.  Note that the coatings themselves - 
regardless who makes them and from what they are made - are nothing more than 
molecule-thick deposits of a very delicate film left on the optical surface 
from a vacuum process in which air is evacuated and the gases of the coating 
materials are gently and uniformly distributed across the glass surface after 
the vacuum container is void of air. 
  This system is devoted to the cleaning of large astronomical refractive 
optics: lens, corrector, and other optical glass; however the techniques 
discussed here as well as the new ASO SuperPlus Solution is excellent for the 
cleaning of eyepieces, eyeglasses, binoculars, camera lenses and all other 
fine coated optical surface. 
  So....the ground rule here is:  CLEAN ONLY WHEN ABSOLUTELY NECESSARY.  In 
most cases, dusting alone will lead to tremendous improvement in performance 
and overall light transmission. 

PREPARATION TO CLEANING 
DUSTING OPTICAL SURFACES:  Large area optical surfaces are frequently plagued 
by DUST, POLLEN, GRIT, DEBRIS and even human skin and airborne hair.  If the 
surface of the glass is allowed to be exposed at a temperature BELOW THE 
DEWPOINT, these particulates will stick to the glass and will be stubborn to 
remove.  However, for optimum performance, it is essential to, indeed, remove 
debris from the optical surface.  Your optical glass MUST be dusted when: 
1) a flashlight held obliquely against the glass reveals a uniform and fairly 
thick layer of dust, etc 
2) when POLLEN is on the glass, as leaving pollen will result in "pollen sap" 
leaving a very difficult-to-remove stain on the surface 
3) ALWAYS prior to cleaning the glass with the solution and technique which 
follows. 
Never clean optical glass without gently dusting first! 
You will find in 3 out of 5 cases that merely dusting off the glass is 
sufficient to greatly enhance your performance back to optimum and that 
further physical cleaning is NOT necessary after dust removal.  There can be 
a lot of smudges, stains, flecks and streaks on the glass before it actually 
begins to degrade your optical performance for all but the most exacting (i.e 
., high resolution planetary imaging, CCD spectrography and photometry, etc.) 
demands put upon your telescope. 
To dust, use a SQUARE-CUT (not a tip-cut) very soft brush that is about 2" 
(50mm) wide with tapered bristles.  I have found several excellent such 
brushes at Lowe's and Home Depot and other stores where quality painting 
supplies are sold.  Look for the very soft and flexible "touch up" and/or 
"delicate trim" brushes....most of these are short-handled and have the 
bristles as an angled radius cut.  Make sure that the bristles are incredibly 
soft; I use the "cheek method" for testing softness:  take the brush out of 
its package and push the tiny ends of the bristles hard against the cheek of 
your face....if they do not "prick" then they are fine for optical use.  
Another tip on selecting a brush is the number of bristles....the MORE 
bristles on brushes just described, usually the softer and better the quality. 
I start dusting by dusting the METAL SURFACES that surround the optics, 
ridding them of all debris first; just whisk away.  Then start at the top of 
your glass and gently swipe the surface IN ONE DIRECTION....do NOT move back- 
and-forth with the brush.  Stroke in only one direction.  Do NOT rub.... 
merely "pull" the brush across the surface and apply no pressure; let the 
brush do the work for your.  Any particles that do not come off with such 
brush will be removed in subsequent cleaning with liquid if necessary. 
The object of your dusting is to essential "move" all the particles to the 
bottom of the surface you are working on...once there you can brush them off 
the area and actually assist their removal by blowing gently against the 
areas being brushed. 

USING COMPRESSED AIR:  DON'T.  Period.  Dusting is easy, although it may take 
a little more time, and it is more effective.  I have found that compressed 
air is virtually worthless for attempting to gently remove embedded particles 
on a glass surface and the chances of the liquid propellants within the can 
being expelled in liquid droplets against the glass is quite great. 

The ASO SuperPlus Optical Cleaning Solution - how to mix it yourself! 
There is NOTHING magic about the new concoction developed over a period of 
about five weeks here at the Arkansas Sky Observatory.  SuperPlus Solution 
is quite simple, and indeed, there are many familiar components that are 
being used that have been touted in cleaning solutions before.  Nonetheless, 
after hundreds of elixirs and hours later, this combination - in exactly the 
proportions given below - results in near-perfect results every time! 
 In striving for the "perfect cleaner" the following criteria were evaluated: 
1) Streaking - the solution was required to dry streak free with minimal "dry 
rubbing" which can damage optical surfaces 
2) Spotting - the solution must dry spot-free with minimal rubbing 
3) Safety - the solution was required in all respects to be totally 
impervious to the optical coatings and totally safe for all variations of 
them on the market 
4) Simplicity - it needed to be something that anyone could mix up when 
needed with over-the-counter inexpensive components 
5) Sure-fire - it must work every time the first time....the less rubbing the 
better. 

Experiments on all types of optical glass surfaces were conducted with EVERY 
cleaner offered by all makers and groups; the following SuperPlus Solution 
was derived as the "best of all of them" since all had some attributes that 
were worthy, with some extreme cases omitted.  Interestingly although some 
of the solutions that have been previously offered were deemed very hazardous 
to the quality of cleaning and even the surfaces themselves, some components 
used within those solutions did HAVE MERIT and have been incorporated!  You 
will be surprised perhaps at the simplicity of this. 
HERE IS WHAT YOU WILL NEED: 
Nearly all components should be available locally; suggested outlets for 
obtaining these are in parenthesis. 
1) distilled water (supermarkets) 
2) "pure" isopropyl alcohol (pharmacies, drug stores....may have to be 
ordered) 
3) coffee filters 
4) "regular" Windex, the blue kind (supermarket) 
5) Kodak PhotoFlo solution (camera and photo houses only) 
6) pure combed cotton surgical swabs (some finer pharmacies, medical supply 
companies....ask your local M.D.!!) 
7) two "atomizers" or simple squirt bottles for dispensing liquids  (Wal Mart 
or similar) 
8) box of KLEENEX [only!] pure white, no additives tissue (supermarket) 
9) quart mixing jars, very clean and sterile (try your cabinets!)    10) 
sterile eye dropper (drug store). 

 NOTES ABOUT THE INGREDIENTS: 
What an how you combine these components, as well as HOW you use them will 
make or break your success in streak-free and perfect cleaning; please make 
note of the following: 
 Pure Isopropyl Alcohol - NEVER use "regular" isopropyl alcohol.  Isopropyl 
is what you commonly see in stores as "Rubbing Alcohol."  However, most 
on-the-shelf varieties is about 70% or less pure....the remaining 30% is 
impurities which WILL result in streaking and deposits on your glass.  USE 
ONLY 91% OR HIGHER proof isopropyl....this is found on the same shelf 
typically, in very large and well-stocked pharmacies.  If not, simply ask 
your pharmacist to order some!  Expect to pay about double the price of the 
"store brand." 
Windex - Many cleaning formulae suggest Windex, indeed from one of the 
largest optical houses in the world.  However, there has always been 
"something wrong" with Windex in that it leaves a ghostly film on optics.  
After much experimentation, I have found that it is the heavy impurities that 
are SUSPENDED in the solution that are responsible for the fog....you CAN get 
them out as you will see.  NOTE that ONLY the blue Windex should be used.  
NEVER use any cleaner with vinegar on your optics. 
Kodak Photo-Flo - If you have never used this before NOTE!!!  This is 
extremely concentrated stuff and a tiny, tiny bit goes a very long way!  We 
are talking DROPPER amounts here....NOT ounces.  DO NOT USE MORE THAN 
RECOMMENDED....your results will be horrible. 
Kleenex - ONLY USE pure white Kleenex, no other brands at all.  Do not select 
Kleenex with "ultra softeners" or with scented oils.  Only plain and simple 
pure white. 

HERE IS HOW TO MIX ALL THIS STUFF: 
You are making TWO solutions: 
1) Solution 1 - Cleaning Solution:  This is the active part of the cleaning 
and should be mixed very precisely in the quantities provided. 
2) Solution 2 - Rinse Solution:  This is ABSOLUTELY necessary for most 
cleaning session; however, you MAY find that you do NOT NEED the final 
solution if your optics dry streak-free (which likely they will!). 
SOLUTION ONE:  Cleaning Solution.  
You are going to have much more solution of each component than need for one 
quart of final SuperPlus Cleaning Solution.  Keep all left-over unused and 
unmixed components well sealed and marked for future use. 
Step 1:  FILTER THE WINDEX VIA THE COFFEE FILTER into a thoroughly washed and 
dried container; go ahead and filter the entire bottle as this is much 
simpler and more effective than attempting to filter one ounce. 
Step 2:  FILTER THE DISTILLED WATER using a second clean coffee filter into 
another jar.  Yes, I know that distilled water is supposedly inclusion free, 
but trust me on this one. 
Step 3:  MIX...... In another  quart jar, add the following (do NOT substitute 
nor change amounts!) 
a) the filtered and purified WINDEX - 1 ounce 
b) ALCOHOL - 1.5 ounce 
c) PHOTO-FLO - two drops...that's RIGHT, I said "two drops"....any more and 
you will be sorry.  And I mean SMALL drops!! (about 1/16th ounce is pushing 
the limit) 
Step 4: MIX together gently but do NOT shake. 
Step 5: ADD 12 OUNCES OF Distilled water.  I chose to mix my solution in empty 
quart plastic alcohol bottles; if doing so, merely fill the bottle to within 
1" of the top. 
 Step 6: Pour liquid into your MARKED squirt bottle for use. 
SOLUTION TWO:  Rinse Solution. 
In 12 ounces of filtered distilled water add TWO drops (only!!) of Photo-Flo 
solution.  No more no less.  Transfer liquid into SECOND MARKED squirt bottle. 
You are now ready to CLEAN your optics. 
The ASO SuperPlus Cleaning Technique - You CAN do it right!  The FIRST time! 

**tip #1** 
CLEAN OPTICS ONLY IN THE DAYTIME WITH THE OPTICAL SURFACE "LOOKING" OUT OF A 
WINDOW OR TOWARD A BRIGHT OPEN SKY 
**tip #2** 
NEVER....NEVER...ATTEMPT TO SURFACE CLEAN LARGE OPTICS WHEN THE HUMIDITY IS 
ABOVE 65% !!  Streaking will result.  If you attempt to clean your optics 
when the humidity is high, you will be very disappointed in the results. 
**tip #3** 
PLAN TO USE AT LEAST ONE TISSUE PER INCH APERTURE BEING CLEANED....ALWAYS 
keep a dry tissue to the surface for best results! 
There is no solution that will result in satisfactory cleaning if your 
technique is NOT good when cleaning.  Unfortunately with cleaning large glass 
surfaces, you must normally move quickly, but gently in order to obtain a 
streak-free and spot-free result.  If you follow this technique, you can move 
a bit more slowly and deliberately AND achieve the same results. 

** MAKE SURE YOU HAVE DUSTED OFF THE PARTICLES FROM THE GLASS PRIOR TO 
FURTHER CLEANING!  (see above) ** 
STEP ONE - Turn your telescope so that you are FACING the corrector plate or 
lens head-on; you are NOT going to use so much liquid that you need to be 
worried about cleaning solution getting away from you and down inside the 
retaining rings of the optics.  Make yourself comfortable....you may be here 
a while!  I prefer placing the telescope if possible in a position where I 
can sit down to clean.  You must have a small table or area within reach 
where you will have your cotton pads, solutions and Kleenex waiting. 
STEP TWO - Imagine your corrector plate or lens in QUADRANTS or quarters, 
like large sections of pie.  You are going to begin at the TOP left and work 
your way down to the BOTTOM left piece of pie. 
STEP THREE - Gently shake the container (Solution ONE - Cleaner) for just a 
brief moment and spray a generous amount of liquid onto the COTTON PAD, NOT 
the glass surface.  You want the cotton pad WET, but not dripping; make sure 
you hold the pad only on ONE side and do not TURN to use the side where your 
fingers have been. 
STEP FOUR - Begin in your upper left "quadrant" and gently daub (do NOT rub) 
this section until you have generously smeared the cleaning solution across 
the surface of ONLY that area.  Never "push" the cotton pad, only pull.  Do 
NOT rub.  The idea here is to ONLY move the liquid across the surface to 
break the adhesion of film and dirt deposits against the glass. MOVE QUICKLY 
TO STEP 5..... 
STEP FIVE - Before the liquid begins to collect into large areas and before 
any drying takes place, immediately begin wiping the quadrant just soaked 
with KLEENEX tissue to dry it....to do this, you want to gently PULL the 
Kleenex across the surface in ONE DIRECTION ONLY...do NOT go back and forth 
as this will streak and will tear the tissue into endless amounts of clumps 
that will have to be removed from the surface.  You will see the liquid 
rapidly drying behind you.  Follow each swipe IMMEDIATELY with a DRY Kleenex 
tissue. 
[reminder:  keep changing to a dry tissue constantly!!] 
STEP SIX - When entire quadrant is reasonably dry, buff gently with a totally 
dry Kleenex; repeat a second time with another Kleenex while gently "puffing" 
a bit of your breath against the corrector plate or lens to expose possible 
areas of streaking. 
[reminder:  keep changing to a dry tissue constantly!!] 
STEP SEVEN - Repeat same procedure on remaining three quadrants with a bit of 
overlap on each. 
[reminder:  keep changing to a dry tissue constantly!!] 
STEP EIGHT - Check each point where areas overlapped during cleaning and 
"touch up" using a fresh cotton swab sprayed with a VERY SMALL amount of 
cleaner....you want this swab nearly dry, but just enough moisture to touch 
up defects in cleaning. 
STEP NINE - Using your breath as a guide, gently "puff' against the glass 
while using a COTTON SWAB to buff the final cleaned surface to a high luster 
with not streaking! 
STEP TEN - [[OPTIONAL]] - USING THE RINSE SOLUTION 
This step is likely NOT necessary and should ONLY be used if there is any 
streaking left after the careful cleaning procedure outlined above.  If there 
are problem areas, you should rinse your cleaned corrector/lens as follows: 
    - spray a VERY SMALL amount of cleaning solution onto the glass OR place 
some on a fresh cotton pad.....you want only a tiny amount of liquid present 
to break the surface tension of the glass....remember, the glass is already 
cleaned from the CLEANING PROCEDURE.  All you are attempting to do is to 
remove any streaks at this point. 
    - gently rub the cotton pad across the entire glass area quickly but 
very lightly and follow WITH YOUR OTHER HAND a fresh dry Kleenex tissue to 
absorb any moisture remaining from the first pass.  This should take care of 
streaking very quickly. 
  - again, buff the entire surface with a fresh and dry cotton pad to 
finish. 
  ------------------ 

Best of luck and take your time.....this solution and technique will work on 
all coated glass surfaces (NOT MIRRORS) and the solution is ideal as well for 
your binocular, eyepieces and camera lenses. 
The key to success is:  1) take your time; 2) work in small areas; 3) use 
LOTS of dry Kleenex; and, 4) use ONLY the materials and techniques described. 
Another quality service from your Arkansas Sky Observatory!  
Part II (coming soon...):  "Cleaning Telescope Mirrors and Delicate First 
Surfaces" 
Part III (coming soon...):  "Preventing the Need to Clean - Protecting your 
Telescope Optics" 
  
Dr. Clay 
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Arkansas Sky Observatory 
www.arksky.org