TELESCOPE AND INSTRUMENT RESTORATION METHODS
AND TECHNIQUES
Jon Slaton
NOTE: this is not a complete primer on restoration techniques;
rather it is a few precautionary notes coming from personal experiences.
First, my compliments on searching out
the correct way to restore your telescope. Second; please read this article
completely before trying any of the methods, as procedures may not be in the
order you may take and skipping a step may diminish your chances of a good
restoration. The first thing I ask people who are contemplating a restoration
of any type is: are you really sure it needs restoring? Many times, a good cleaning,
proper lubrication and adjustments, and possible replacement of worn or missing
parts (mostly bolts, nuts, etc.) will have the instrument ready for use. I had a
clock shop for over 30 years and did thousands of repairs, a few quick fixes, but few full restorations. A thorough
restoration is always costly, time consuming, and without a doubt stressful to
owner and instrument. Proper and frequent lubrication is the key to longevity
for telescopes and other instruments.
I personally do not like to see a shiny
brass tube on an old instrument. It looks like it is new, or at best, looks like
it came from a showcase. I do agree that there are times that stripping
and polishing a tube are in order. I have had a few come through the shop, which
were harshly abused by soldering things on them, painting them pink, or
partially polishing them to where part or all of the lacquer is gone. When parts
have been replaced so that the new ones stand out like a sore thumb, stripping
may be necessary but first try to make the new parts match the old ones. My
first rule when restoring anything is to leave as much of the original as
possible. This includes not only the parts, but also the finish. Once you decide
to turn a part down in the lathe or file it to make it fit a new piece, you can
never put it back. The best policy is to make the new piece fit the old. If you
cannot make the replacement part fit the old one, make a completely new piece
from scratch. Remember, restoration is not a quick fix, it is costly and time
consuming.
Pits, dings, and scratches show some of
the history of an instrument. (Sorry antique tractor and car restorers. I know
your vehicles really look great but obviously very few, if any older things
survive without a scratch.) In addition, a proper patina will camouflage the
imperfections nicely, and that includes using Lemon or Tung Oil to coat the
instrument. If you have dents or dings that impair the functions or movement,
such as on a tube, you can turn a piece of wood on a lathe to just fit the
inside diameter of the tube. Remove ALL screws and stops from the tube, and
drive the wood through, being careful not to cause any further damage.
I have made a series of wooden wedges (they
look like torpedoes) in order to smooth out tube dents - starting with one just
big enough to start pushing the dents out, and getting a little bigger each
time. If you try to push all the dent out at one time, things may not turn out
as you expected. You can
use this same procedure on flat or curved pieces by making the wood fit the
original shape, then pressing or hammering the wood together with the brass in
between. If you try and use a hammer on the brass, it will surely dent and have
lots of small dings where before you had one big ding.
Many times the brass does not need
polishing, it only needs cleaning. Be cautious as to what you use
- ammonia
products will eventually eat away at the brass. I have seen brass works from
clocks virtually ruined from soaking in ammoniated solutions. I assume these
were especially dirty and were left in overnight or longer, but still the cause
and effect are clear. Do not use window cleaners, as they too have ammonia. Try
warm water with soft liquid soap added in, and lots of time and clean rags. The
tendency is to go ahead and use something stronger, and clean it off when done.
To do so you are harming the very thing you are trying to preserve. There are
some brass cleaners, which specifically state for brass, but upon reading the
labels, you see they do indeed contain ammonia. Not to say that ammonia does not
clean brass - it does, but rather you need to look at the long-term effect on
the brass.
I do not use any type of
buffing wheel or the like, as it is easy to very quickly remove square edges,
ending up with rounded corners and smoothed out details. A few passes with the
buffing wheel and some of the lettering is almost illegible. The names engraved
in script on the faceplate of one of my telescopes is so delicate that a small
amount of polishing will probably remove the faint ends of the script. Avoid
using polishes which are in padding or wadding type, as they seem to polish
rather aggressively. Find a cleaner that does not attack the brass. It might
take longer to polish, be harder to use, and not clean as quickly, but you
minimize the risk of permanent damage. As a side note: I don't polish brass or
silver any oftener than absolutely, as you have to notice the black on the rags
when you polish it: the dirt is part of the metal which is removed by the
polish. Clean and/or polish the tube assembly to your liking. Depending on
how much polishing or cleaning you have done, it may look like a new piece of
brass. Clean out cracks with a soft toothbrush, and use toothpicks or
whatever to get the cleaner from screw heads and other tight places. It is
imperative that you clean the brass thoroughly. I use lacquer remover,
acetone, Xylene, or some other strong solvent to make certain that every trace
of the metal polish is completely removed. (Use
masks and/or other precautionary measures for your safety.)
The brass must be almost
surgically clean. After you are sure it is this clean, wipe it down with another
clean rag just to be sure. Then use lemon oil
or tung oil. (Plain tung or lemon oil, nothing else in with it.) Use a clean soft
cloth to apply the oil on the brass. Let
it sit for a bit and then rub it down gently until most of the oil is removed. I
let it sit for a day or so, and then I reapply the oil, rub it down again, and
let it sit again for a few days. You can gradually lengthen the interval between
applications to where you finally do it maybe once a year. The brass will
gradually darken and have a nice patina. I have not had any corrosion using this
process. If you miss a place and some of the polish remains, it will soon show
up but you can clean it, and apply the oil finish again without too much
trouble.
I try to do the least amount of
polishing, to a point where will look "right."
I
have used different types of wax, which will last for about a year, depending on
how much you will be using the telescope. Once again, check to be sure there
will be no harm done over time. Some waxes turn green and gunky over time and
obviously are detrimental to the brass. I have used lacquer on brass and bronze
pieces, but I think the oils work better. As a bonus, they are easier to apply.
l will not bore you with many of the problems and solutions I have had. Before I
did anything to my Alvan Clark brass tubes, I checked with people; asked more
people; and called the manufacturer to make sure the product would not attack,
corrode, pit, turn green, or anything else with the brass over time. Sometimes
the answers were rather surprising, considering what the products were being
sold for. I have stripped and re-lacquered one of the tubes twice, and it looks
bad again. I bought lacquer from the people that make the lacquer for top-name
pianos. You would think it would be good. But it spotted very quickly. Big brown
spots right in the middle of the tube. I stripped it, called the manufacturer,
and he told me I probably had fingerprints or something on it. I didn't think
so, considering the care I had taken preparing the tube for lacquering, but I
stripped and re-lacquered it again. Within two weeks it did it again. I called
him back, and he asked me if I had mixed the corrosion inhibitor in with it. I
replied that he had failed to mention it, along with failing to send it. So I
added it, and within two weeks it did it again. Rather than call him back and
ask what else he forgot to tell me, next time I will use Tung or Lemon oil.
Some of the parts, such as the piers, are
simply a cast metal piece and I see no harm in bead blasting to remove layers of
paint. I carefully took layers off a transit base, and preserved a small area of
the original paint so the color would be available for future restorers. On
other places, such as setting circles, silver inlays, etc., I polished using 3
micron Alox in alcohol applied with a very soft rag. It works fairly quickly,
but I polish the bare minimum to make the lines or letters show up. I don't
care how careful you are, or what you are using every time you polish
something a small part of it goes away with the polishing rag.
Try cleaning a
new piece of brass or aluminum. Then clean it with Xylol or something. Then
clean it again with the solvent. When you're sure it is clean, use some metal
polish on a new rag. The rag will immediately turn black. This is part of the
metal coming off. That is why I don't polish often and hard. I am not
advocating leaving dirt and grit on instruments, just be careful as to how much,
how often, and how hard you polish something.
Very clean steel rusts quickly, so it is
important that you must protect it from rust.
Important
restoration techniques
I begin
by stripping down the tube assembly and mounting, taking lots of digital
pictures, along with detailed sketches and notes.
It sounds
like a waste of time to do it, but I write down everything about how I took each
piece off or apart. During reassembly, your notes can be a real lifesaver
because they can tell you that you need to put a certain piece on before you put
the one in your hand on - even though it looks just the opposite. I managed to
forget a piece and had to take apart the whole mechanism on a clock drive just
to put a spacer in which looked like it should go on last.
Bolts, nuts, screws, and other
small pieces look identical, but often are not interchangeable. I once had the
Making and repairing parts,
and modifying and using tools properly
Many
times, there will be parts missing, or perhaps replaced with newer parts which
may or may not be obvious. These things really take up your time. Try to locate
another instrument like yours, or at least study other instruments and see just
what is missing or replaced. I hope that you will have a good idea then of what
the piece should look like, and how it should function. It is hard work
designing a missing piece; it is also not easy to repair an old one.
Note that brass comes in several varieties - try to match
what was there. Sometimes the piece is there, but bent. This can be
especially frustrating. The tendency is to bend or hammer it back in place, and
hope for the best. The problem with this attack is that it is just that - an
attack. First, ascertain just what caused the piece to bend or break in the
first place. Usually you will find that it is due to one of two causes: the
operator did not know or tried to exceed the limits of travel of the piece; or
the piece was stressed to the point of damage due to friction. (read: lack of
proper lubrication.) Try to fix the underlying problem first, then work on the
damaged piece. Many times brass will break if you try to bend it. Try heating it
a little and gently see if it will bend back. If not, heat a little more. You
may need to anneal it. I use leather or cardboard linings in
my vice or pliers when working with brass, as it seems to scratch so easily and
removing those marks I just made is really frustrating when they could have been
avoided in the first place. Broken
pieces are repaired by silver-soldering. I have found that usually silver
solder, even though not the same color, barely shows after repairs
- if you are careful and do not get it all over everywhere.
Use enough to make a good connection, but not too much. This is one of those
times where you may need to practice on a few test pieces to see how it works
before working on the actual instrument. The joint is
strong, so if the piece is bent as well as broken, try fixing the break first
then try straightening it, as it will be easier to get it to the correct shape
if it is all there!
Bolts and screws, as mentioned before, are rarely interchangeable.
Oftentimes the first person to take them apart marked them with a series of
small dots, or punch marks. You will notice that (usually) if there are say 6
bolts in a pattern, one is punched once, one twice, and so on until you get to 5
punches. One is not marked. Please use the correct tool for the job. All too
often screw heads are seen with gouges halfway or two-thirds of the length of
the screw head slot. This is caused by using the wrong screwdriver blade. Buy
a good set of screwdrivers, and keep them separate from your regular
screwdrivers, because you are going to file or grind them for instrument use
only. Get a magnifying glass and take a good look at a screw head slot. Take a
screwdriver, which is the same width as the slot. If you don't have one the
same width, use one a little wider. File or grind the sides down to make it the
same width. Then start on the thickness and shape of the blade. The blade
should fit the slot all the way down to the bottom of the slot, one end to the
other, and the sides of the blade should touch the sides of the slot all the way
from bottom to top. This fitting of the tool to the screw ensures that you will
have maximum torque available to remove and reinstall the screw with the least
chance of damage. If the screw does not readily unscrew, apply penetrating oil
and let it soak for a while. I know, it is such a time waster because you only
have one screw left to remove, but it is better to have all 6 original screws to
use again than to have to make one or more. The same advice goes for bolt heads,
nuts, and any adjusters on the instrument make your tool fit the instrument,
not the other way around.
Which
brings up the next subject screws or bolts. Sometimes they simply will not
come out without damage, or maybe they were missing to begin with. I try
probably harder than I should to match the old screws. Many people see nothing
wrong with retapping a slightly larger hole and using a newer, readily available
screw. I have done this when the threads are stripped or an replacement simply
could not be made. But if I can, I make a new one. If you do not have a sample
to go by, you can take a piece of round wood and make it slightly larger
diameter than the hole.
Round the
end a little, and thread it in. If you are careful, you can then unscrew it and
have a thread pattern to go by.
If the
screws are all there, but are damaged, you can make them look and function
better by carefully and lightly tapping the metal back into shape. I am assuming
the screw heads were damaged by an ill-fitting screwdriver. Take a very fine
file and clean out the screwdriver slot. The same thing can be done to pieces that have
been hammered on, dented edges, etc. Notice that brass is a soft metal
and dents easily with a hammer. If you are trying to straighten a bent piece,
use a piece of wood between the hammer and the brass the wood will take the
brunt of the force, and the brass should not dent from the hammer blow. It is
not as easy to un-dent. The metal parts of the instrument which are flat usually
have a pattern to it. This is called the grain, and most metals have grain just
like wood. When polishing or cleaning, go with the grain. If this is not clear,
get a new piece of flat rolled brass or steel and look closely at it. You will
see the grain. Polish it, and go with the grain. Clean it to where it shines.
Then polish it just a little across the grain. Clean it again and look at it
you will see that where you polished it across the grain it looks scratched.
Enough said.
Most
types of focusers should be greased and/or oiled regularly. One of the major
causes of damage in using older telescopes is that they are too stiff to
use. This applies not only to the focuser, but to the whole thing. The tendency
of many people is if it won't move easily, a little more muscle won't
hurt, so force it. I have used specialty waxes on some focusers, and light
grease on others. Either way, keep the parts to where they work freely without
having to force them. Clean the old oil or wax off regularly and reapply as
necessary. A buildup of anything causes binding. Many focusers
have a small piece of felt surrounding the drawtube. Make sure this felt is not gummed
up with anything, especially tiny pieces of dirt which act just like sandpaper. Incidentally, I have seen some
focusers which use a special sticky grease. If you clean them and use something
else, they seem to have a lot of play and don't work properly. I have only
seen these on new(er) telescopes.
When reassembling the telescope do
not force shafts into bearings, or any other parts together. They should fit
snugly, and if they don't fit then something is wrong and needs investigation.
Check for play in bearings, worn bushings, and gouges or prick marks on seating
faces. Make sure worms are properly aligned with the wheels, and that the teeth
are correctly meshing. Worm wheel teeth should have a mirror finish. It almost
goes without saying that you need to have everything absolutely clean prior to,
and during assembly. A flat surface which is used for something else to slide or
rotate on needs to be flat, or at least even. This is one case where you might
need to remove some of the original material. Dirt and grit can get into or
between the surfaces and the dirt causes the surface to have raised areas, like
prick marks. These areas need to be flat. You don't necessarily need to smooth
it down to where all the gouges are gone, as many times any removal of metal
will cause the mating part to be in the wrong location. You do need to remove
the high spots, though, on both parts. I have found that many times a surface is
used for a bearing surface and then painted right up to the area where it turns
or slides. These are very difficult to repaint, and remember that the
working surface needs lubrication of some sort.
Lubrication
Practically all the bearing
surfaces, sliding tubes, the screw threads on knobs, and other places need
lubrication not only to function properly, but also to prevent wear. I cannot go
into every place that needs lubrication, as it is nearly impossible to come up
with every occasion. Check the instrument over, and if something rubs, slides,
contacts, or threads into or onto another part, chances are it needs proper
lubrication. There are some important exceptions: gear teeth are usually meant
to run dry. The ends of gears (pinions), where they go through the side plates, are to be
lubricated. Worm wheels are usually meant to run dry, and they are also meant to
be run clean. By the way, when you are cleaning gears and worms, don't use a
screwdriver, awl, wire brush, or anything hard to clean the gunk from the teeth.
Once again, use a toothpick, or let it soak in oil a bit to loosen up the offending
material. After all, these are precision made pieces and you don't want to
scratch them up. If you do, you take the chance of introducing errors, uneven
tracking, or even stopping the instrument.
There are various types of oils and greases. Check around and ask to find
out which will work best for your application. Be careful, as some lubricants
will squeeze out if much pressure is applied. On some of the larger telescopes,
there is a lot of weight and torque on the shafts, and it takes special oils and
greases to remain in place. Just because the label says for everything under
the sun does not mean it will work in your thing. Likewise, some things need
the thinnest of coatings, and you would not want something thick and greasy on
it.
SUMMARY
Stop and think about what you are
doing. Then think it through again. Be sure to take twice as many pictures as
you think are necessary. Digital pictures are cheap. I thought I took way too
many, yet missed an important angle last time. Before disassembly, ask yourself
if you are capable of doing the whole project. From having the clock shop all
those years, I can tell you it is very hard to take a box full of parts someone
started working on, and then making a working mechanism out of them. Usually you
have to fix the problems the last person caused, then fix the original problem. With
something like telescopes, it is much the same thing but compounded with the
added problems of optics.