these before you place an order, send me an email, or post one of these
question on my Yahoo group. Thanks.
is your lead time?
it is about 6-12 months for new mirrors (depending on size, larger
mirrors take longer), and
approximately 1-3 months for a small-medium size mirror
do you require to place an order?
new mirrors, I ask for 50%-60% of the price up front as a deposit to
cover glass costs (which often include a large secondary mirror) and
the first part of the labor cost, and to reserve
your job's spot in my queue.
-The balance of the purchase price is due upon completion of the
mirror, prior to shipment to the coater.
refigures, if the cost is relatively low I will ask for full payment
upon completion of the refiguring, prior to shipment to the coater.
If the cost is higher, such as for a large mirror, I may ask
for a deposit based on the
estimated cost of the work.
BUT only after I have a buyer for the mirror that your ordered and have
cancelled. Glass is not cheap, and I have to buy glass to
mirror. Consider this carefully if you are ordering a custom
mirror that may be unsuitable for other people's projects, and
therefore hard to sell. I will not sell you a
mirror for a reduced price.
What advice do you have on mirror coatings?
mirrors 20" in diameter and smaller, I recommend and use Nova
Optical Systems for standard and enhanced coatings.
-For mirrors 22" to 46" in diameter, I recommend and use Optical
for enhanced coatings. They are also only a few hours drive
away from my shop, which reduces shipping costs for larger projects.
listed above have done optical
work, and understand how to strip old coatings safely and treat a
polished surface without damaging
is the mirror owner's responsibility to have the mirror recoated in a
timely manner by a good coater. Do not let your coating
to the point that they become unusable - this can result in chemicals
etching the glass, and the degraded coating may be very difficult to
strip, risking damage to the optical surface. If this occurs,
mirror may need to be refigured to polish away the remains of the
coating and the possible damage to the glass, and this is generally
done at additional cost.
-If there is an issue with stripping the
coating, the coaters above will let me know, and I can perform the work
necessary to restore the figure of the mirror.
Again, this work is done at additional cost to the
owner, so don't let the coating go too long.
you wish to have your mirror coated or re-coated by a company not
listed above, please consult
me first. If something goes wrong with the stripping of an
old coating or a new coating, some coaters may take
measures to remove the residue before recoating. This can
the figure of the mirror. After
the initial coating, I cannot and will not be held responsible
for damage to the optical figure/surface caused by a coater,
you wish to use a different one, choose carefully and do so at your own
do not recommend silver or other metals for telescope mirror coatings.
Some coaters may not be used to removing these metals before
recoating, and they may damage the glass. While silver may
initially offer higher reflectivity, I hear that if often fails earlier
than an aluminum coating, especially in environments near the ocean or
in high humidity.
-I do not recommend
or specify chrome undercoats for aluminum coatings. Chrome
is sometimes applied first, in the vacuum chanber. In this
environment, with no air to react with the chrome, aluminum sticks very
well to it.
So, if the aluminum won't stick to the glass, chrome may used as a
"band-aid" - but only once. While the aluminum can be
off of the chrome, aluminum will not stick to chrome that has
exposed to the environment, so it is useless afterward. To
it worse, the chrome is not easily strippable without risking damage to
the glass surface through harsh chemical action.
line, if aluminum won't stick to the glass, then the
not clean or it is damaged in some way. Choose your coater
you recommend standard or enhanced aluminum coatings?
have never had a bad experienced with the normal enhanced coatings
offered by both coaters listed above. In theory, the extra
in a properly applied, simple enhanced coating should make it a little
more durable than
a non-enhanced coating.
-Even if there is a coating
issue, these coatings are easy to strip off without harming the optical
surface (by a competent individual or coater), and are easily recoated
after that. NO coater is
perfect, but the ones I use stand behind their work.
-I recommend enhanced
coatings for secondary mirrors, and for telescopes that have three or
more mirrors to reduce light loss. Ideally for a Newtonian
secondary mirror, the coating is designed for reflection at 45 degrees,
and will be different than one used at normal incidence (0 degrees).
-I recommend standard
coatings (overcoated aluminum) for Newtonian primary mirrors for one
simple reason - lower cost. If you don't mind
little extra, then I can recommend enhanced coatings from the coaters
regrind my slow mirror into a faster mirror?
the mirror has massive problems, it does not usually make financial
sense to destroy an optical surface just to make a new one.
-The client will probably come out ahead if he/she sells the mirror
that they don't want and simply buy a new one from me.
Do you only
make and refigure fast mirrors?
I'll work on mirrors of just about any focal ratio. I enjoy
making or refiguring a slower mirror now and then.
How much will
it cost to refigure my mirror (which you have never seen or tested)?
-I can't give you an estimate
until I test the mirror.
rates are by the hour, so cost depends on how much time I have to
devote to the project. I believe this is fairest to both
and the client.
-After testing, I will provide an upper and lower
bound for the cost, and the client can either proceed or I can return
the mirror, and the client will pay for the testing and shipping.
methods do you use?
concave mirrors, I test most frequently with knife-edge/zonal testing,
also known as Foucault testing. I have found that, even for
mirrors, this testing method is extremely accurate when used properly,
and provides results that agree with star testing to high accuracy.
use a proprietary, highly-sensitivity test to check the figure of
revolution of each optic at multiple stages in the work.
-I have 12" and
flats, which are used for autocollimation.
-I have 10"
f/12.5 and 10" f/6.4
reference spheres that can be used to test flats to high precision.
-I test all blanks for
strain with a crossed-polarizer test.
-I have a Buccini MIC-1 spherical wavefront interferometer, a variety
of divergers, and coated and uncoated reference mirrors. I
test uncoated or coated optics, and I can test Cassegrain systems in
double-pass autocollimation with one mirror uncoated.
I ask that you use my mirror under the sky, support it properly,
collimate it well, cool it to equilibrium, and evaluate it with star
testing and by observing the sharpness and clarity of the images.
So far no one has been disappointed with what they see.
-I value customer feedback - this is a form of testing.
Please let me know how my optic is performing.
How much does
a small mirror and matching flat (diagonal, secondary, etc) mirror,
cost will be around $100 plus shipping. Larger primary
and flats over 10" in diameter will
require more time, and are closer to $200. Again, this is
the hour, so more complicated tests will cost more. Please
your mirrors before sending them to me so that I will not have to.
Others test mirrors for free - why don't you?
charging a testing fee shows that both the owner and the optician are
serious about doing the testing. Second, others don't have a
backlog of work - I do - and time spent testing is time not spent
polishing. In my opinion, you get what you pay for.
How should I
pack my mirror?
provide test numbers for a mirror?
inevitably they end up on the internet, where "experts" will "debate"
them without consulting me.
-For telescope mirrors made by me to my highest standards, I
guarantee performance to 50 power per inch of aperture on nights when
the atmosphere is steady enough to allow this, so long as the
mirror is properly supported, equilibrated, collimated, and reasonably
clean. When you experience a night that allows this type of
of my optics, you will forget all about the numbers.
ordered with a less stringent specification (which is often appropriate
for non-astronomical uses) are guaranteed to that specification.
you have a question about a mirror that I have made, such as in the
case that you are buying a used mirror, please contact me so that I can
consult my records to see the specification. You will need to
provide the serial number and the size and focal ratio of the mirror.
don't you make small mirrors?
not set up for it, and others are properly equipped and will do a good
job. I am set up for ~14.5" mirrors through 60" primary
and I make smaller custom Cassegrain secondaries. I also
tested elliptical flats to go with my primary mirrors so that the
client can be sure that the entire optical system is up to my standards.
-I will refigure mirrors
of just about any size, though I prefer to work from 10" and up with my
other things should I know about your optics?
new mirrors, I grind the back of the blank smooth with very fine
abrasives before optical work is begun. This makes them look
better, allows them to be cleaned more easily, and the mirror will then
"slide" nicely on mirror cell supports without binding.
also scribe, permanently with a diamond-tipped scribe, a small
circle in the glass, exactly centered on the mirror after carefully
centering it on a turntable. This helps you locate your
triangle, ring, square, or other shaped sticker on the mirror for
is the difference between Pyrex and Supremax?
is basically the same as Pyrex in terms of chemical composition,
coefficient of thermal expansion, and how it reacts during optical
work, polish quality, etc. It is made by Schott.
a higher-quality product than some sheet Pyrex was, though the Pyrex I
have used was always very good in quality. Benefits (compared
to poor quality Pyrex, which I never used) include fewer striae,
(stuff in the glass), and bubbles.
-Supremax is available up to
~2.5" thickness, which is more than the ~2.25" maximum of
That's good for me, because I make big mirrors. The largest
mirror that can be cut from a sheet of Supremax is ~44" in diameter.
-Supremax is readily available - Pyrex is no longer available in large
end user will notice no difference in most mirrors, except somewhat
higher prices for mirrors because the material costs more.
size secondary should I use in my telescope?
can't answer that question unless I know the measurements of the
instrument, the required fully illuminated field, etc. In
general, the telescope builder is the one that determines this.
What scratch/dig rating do you provide, and what is your policy on
-For new telescope mirrors 32"
and under I usually achieve a scratch-dig rating of approximately 20-10.
-Also, almost all new mirrors that I make in these sizes have no
scratches or sleeks.
it is impossible to completely avoid the occasional cosmetic blemish in
the form of a few small residual pits, bubbles, or sleeks, so for
normal telescope mirrors, I do not promise a perfect, blemish-free
surface. However, any blemishes that are present are merely
cosmetic, and while they may be visible on the surface of the mirror,
they will not affect the images formed by the telescope, so there is no
reason to be overly concerned about them. They have less
on the image than a few minutes of dustfall!
-On larger mirrors,
more factors come into play. It is far easier to miss
and since the polishing time is longer and the area of the mirror
larger, the chance of getting a sleek increases. Sometimes
glass itself may have more defects that I cannot control. So,
these larger mirrors, I do my best and typically achieve better than a
60-40 scratch dig.
-It pays greater dividends, in terms of image
quality, to spend time tweaking the figure of the mirror, which will
affect image quality, than it does to worry about some cosmetic
blemishes that will not affect image quality.
-In certain glass,
especially surplus quartz blanks, bubbles are common, and I cannot
guarantee a bubble-free optical surface because I cannot reject an
expensive and difficult-to-get blank just because it has bubbles.
refigured mirrors, I generally improve the polish quality of the
mirror, but don't any pre-existing scratches to go away. If
are sleeks or scratches that you wish to have removed, then this
generally requires many, many hours of polishing or regrinding, which
will greatly increase the price of the work compared to the price of
-If you have a scratch/dig
requirement for a particular application, then please specify it when
requesting a quote and I will quote appropriately.
-If no value is specified,
then I will assume a value appropriate for the use of the mirror.
For mirrors that are simply collecting light, a perfect
not necessary, and will unnecessarily raise the price of the optic.
For telescope optics, the mirror will be thoroughly polished.