Meade Telescope TMB 92 User Manual

camel’s hair brush with attached blower bulb, for example).  
The use of canned or compressed air should be avoided, if pos-  
sible, as the propellant in the can may spit out and leave diffi-  
cult-to-remove deposits on your lens. Also, the expanding com-  
pressed air drops in temperature as it leaves the can. The cold  
air coming out of the tiny tube that most compressed air cans  
use to direct the air flow has been known to chill a lens to the  
point of spalling chips off the lens if pointed at the same spot  
on the glass for too long.  
If you want, or need, to use compressed air to remove stub-  
born particles, use a high quality compressed air duster (of the  
R-134 propellant type). ChemTronics sells a high-quality unit.  
Do not tip or shake the can. Blow any loose particles off the  
lens surface using short blasts at an angle to the glass, without  
getting too close to the lens surface or aiming directly at it.  
Next, moisten a ball of USP grade pure cotton with a few  
drops of a photographic-quality optical cleaning solution de-  
signed for multicoated camera and binocular lenses. You can  
use Formula MC (available from many telescope dealers) or  
your own mixture of distilled water and a drop or two of mild  
soap. A well-worn 100% cotton handkerchief also works well  
and Zeiss and Kodak both make suitable cleaning fluids. Blot  
the entire surface with the dampened cotton ball or cloth to  
pick up any stubborn particles and to clean the surface. Ex-  
change the cotton ball and/or turn the cloth frequently so you  
always have a clean portion of the cotton ball or cloth in con-  
tact with the lens.  
Use a very small amount of liquid – not so much that the  
fluid could be wicked between the lenses by capillary action.  
Do not drip the cleaning fluid directly on the lens. Do not, at  
any stage, apply hard pressure. Using a fresh piece of cotton or  
a lint-free white facial tissue, carefully clean the surface of the  
lens by wiping across in a radial direction. Repeat the process  
with denatured alcohol, using a blower brush to clean off any  
dust that may fall on the lens as you are cleaning it.  
If you want to take the ultimate step in cleaning, a final rinse  
with high-grade acetone will clean the surface to new condi-  
tion. You may notice a few faint streaks from the dried solvent.  
They will not affect performance, but they can be removed with  
light pressure and a Q-Tip slightly moistened with a small  
amount of alcohol or acetone. Finally, a clean air blower bulb  
can be used to remove any remaining dust.  
wavefront for third order aberrations, and 1/60th wave for sharp  
(fifth order) aberrations. It is highly unlikely that even the most  
ardent observer can see errors of this small a magnitude on an  
extended object, even under very good seeing conditions (which  
is when the atmosphere typically presents no better than a 1/4th  
wave P-V wavefront to the instrument).  
The refractor also presents another factor: the change in  
spherical aberration with a change in wavelength. This “sphero-  
chromatism” is found in all refractors. As a lens is tested in the  
longer (red) wavelengths, the lens becomes “under-corrected.”  
Tested in the shorter wavelengths (blue), the lens becomes “over-  
corrected.” These overlapping corrections at different wave-  
lengths change the star test pattern from technical perfection.  
However, TMB objectives are corrected at the peak visual  
wavelength centered around 560nm in the green-yellow por-  
tion of the visual spectrum. The eye sees over 80% of the vi-  
sual detail at this wavelength. It is the correction at this visual  
peak that makes the difference between a merely good objec-  
tive and a superb one. Our lenses are figured for the best pos-  
sible wavefront at green-yellow wavelengths, for the sharpest  
images and highest contrast.  
TMB Optical TMB-92  
Thoma a  
s M. B ck  
Signature Series  
Congratulations on your purchase of this TMB Optical TMB-  
focuser rotation.  
92 Signature Series air-spaced apochromatic triplet refractor.  
This exceptional 92mm f/5.5 scope uses an element of costly  
FPL-53 ED (Extra-low Dispersion) glass to achieve true apo-  
chromatic visual and photographic performance, free from chro-  
matic aberration and spurious color.  
At only 13.25” in length, the TMB-92 is a premium quality  
ultra-compact refractor that we believe elegantly and more than  
capably fills the void left by the long-discontinued 90mmAstro-  
Physics Stowaway (a legendary refractor that sells for up to  
$6000 on the used market).  
The supplied carrying case is precut to hold the TMB-92 in  
either short body imaging or long body visual configurations.  
FOCUSER  
Your TMB-92 features an ultra-precision Feather Touch  
Model 3025 dual-speed rack-and-pinion focuser from Starlight  
Instruments. This exceptionally smooth focuser has a 3” diam-  
eter drawtube for non-vignetted astrophotography with medium  
format film cameras and very large chip CCD cameras. The  
drawtube ends in a 2” accessory adapter with a non-marring  
compression ring eyepiece/accessory holder that will not dam-  
age the barrels of your 2” accessories. Three hand-tighten lock  
knobs on the adapter assure the compression ring’s solid grip  
on heavy accessory loads. This adapter allows visual use with  
2” star diagonals, plus imaging with 35mm film cameras and  
2” barrel large format CCD cameras.  
The 2” accessory adapter is secured to the focuser drawtube  
by three recessed hex-head screws. Undoing these allows you  
to remove the supplied 2” adapter and replace it with a custom-  
made Feather Touch adapter for medium format (Pentax 6 x 7)  
film photography using A-P photographic accessories. Please  
contact Starlight Instruments directly at (847) 985-9595 for any  
specialized adapters you may need in this regard.  
The fully-collimatable TMB-92’s truly outstanding optical  
and mechanical quality will provide you with many years of  
highly portable visual observing and imaging enjoyment.  
PHOTO/VISUALCONFIGURATIONS  
The TMB-92 consists of an optical tube assembly with lens  
and dew shield, a Feather Touch focuser that slips into the op-  
tical tube and is locked firmly in place by three brass knobs that  
allow 360° rotation of the focuser, and  
a 2.25” extension tube that can be in-  
stalled between the optical tube and the  
While star tests are interesting and useful, they should not be  
the only criterion for judging any telescope’s quality. Most ob-  
servers spend their nights enjoying the views of extended and  
detailed objects – like nebulae, galaxies, star clusters, and planets  
– not simply examining a star test’s single out-of-focus point  
of light. We feel that the true proof of optical excellence will be  
found in your nightly observing, not just in star testing.  
focuser for visual use.  
When the optical tube and focuser  
A FINAL WORD  
are assembled without the extension  
tube, the resulting physically short tele-  
scope configuration provides the long  
back focus needed by those primarily  
The supplied 2” to 1.25” accessory adapter is designed for  
visual use with 1.25” star diagonals, plus imaging with stan-  
dard 1.25” format CCD, webcam, and 35mm adapters. This  
Thank you for your purchase of our TMB-92. We believe  
that this ultra-compact apochromatic refractor will outperform  
any other telescope type, inch for inch, and is the most trouble-  
and maintenance-free telescope that you can buy. Its versatility  
for visual, photographic, and CCD work is unmatched. With a  
little care, this fine apochromatic refractor will last you a life-  
time. Use it to enjoy the wonders of the night sky!  
Supplied  
Extension Tube  
Retracted  
interested in serious CCD imaging us-  
Focuser rotation/extension tube  
lens shade  
lock knob (1 of 3)  
ing long equipment trains: camera, filter wheel, adaptive optics  
system, etc. This arrangement also allows binoviewer use with-  
out the need for a Barlow or optical compensator lens.  
For occasional visual work, a simple optional compression  
ring extension tube (from Astro-Tech, TeleVue, and others) can  
be slipped into the scope’s 2” accessory holder to provide the  
necessary extra physical length to reach focus with a star di-  
agonal and eyepiece.  
2.25” visual extension  
tube installs here  
BRIEF SPECIFICATIONS  
Aperture ............................................................. 92mm (3.6”)  
Focal Length ...............................................................506mm  
Focal Ratio ...................................................................... f/5.5  
Objective Type ...................... air-spaced apochromatic triplet  
with an FPL-53 ED glass element  
Optical coatings .......................................... fully multicoated  
Resolving Power (Dawes’ Limit) ................. 1.26 arc seconds  
Visual Limiting Magnitude.............................................12.3  
Light Grasp Versus the Eye ...........................................173x  
Focuser............... Starlight Instruments Feather Touch #3025  
3” dual speed rack and pinion, with 10:1 ratio fine focus;  
2” and 1.25” compression ring eyepiece holders;  
Hex head  
screw  
attaching 2”  
adapter to  
drawtube  
(2 of 3)  
Avoid overcleaning your scope. The multicoatings on the lens  
are quite hard and durable. However, frequent overzealous  
cleaning can scratch the coatings if all the dust particles (which  
are often tiny flecks of windborne rock) are not removed be-  
fore you start pushing a damp tissue around the lens surface.  
Clean your optics only when absolutely necessary. If you take  
proper care of your TMB-92, cleaning should rarely be needed.  
For those primarily interested in visual observing and only  
casual imaging with a 35mm camera, webcam, or Deep Sky  
Imager-type CCD camera, a 2.25" extension tube (shown above)  
is supplied to provide the proper back focus for comfortable  
visual use and casual astrophotography. This extension installs  
between the optical tube and focuser. Agroove in the extension  
tube engages the large brass lock knobs in the optical tube (that  
normally control focuser rotation) to lock the extension tube  
firmly to the optical tube. Three nylon-tipped metal lock knobs  
at the opposite end  
Left coarse  
focus knob  
THE STAR TEST  
We strive to make the best apochromatic optical systems avail-  
able. You may find your lens may not test “perfect” during an  
extended and stringently-graded “star test,” particularly if the  
scope has not fully reached thermal equilibrium before the test.  
This is not an indication of a poor optic, but is rather due to the  
test star’s complex wavefront continually changing as the see-  
ing conditions in our living atmosphere vary from moment to  
moment.  
and 360° rotating camera angle adjuster  
Focuser Travel.................................................. 2.56” (65mm)  
Tube Diameter.......................................... 114mm (4.5”) o. d.  
Minimum tube Length ................................ 13.25” (337mm)  
(set up for imaging, lens shade and focuser retracted)  
Tube Length ...................................................... 16” (406mm)  
(set up for imaging, lens shade extended, focuser retracted)  
Maximum Tube Length............................... 20.75” (522mm)  
(set up for visual use, lens shade and focuser extended)  
Optical Tube Weight ................................... 8.5 lbs. (3.86 kg)  
Case Dimensions ................................... 22.25” x 12.75” x 8”  
Original focuser  
of the extension tube  
rotation lock knob  
now lock the focuser  
(1 of 3)  
Compression  
1.25”  
ring  
in place and allow  
accessory  
lock knob  
focuser rotation, just  
as the large brass  
lock knobs in the op-  
tical tube do when  
the extension tube is  
not used. A Teflon  
insert in the focuser  
end of the extension  
tube assures smooth  
Extension  
tube  
2”  
accessory  
adapter  
New  
No optic is perfect, and every brand and model scope will  
show some error in an extended star test. The sensitivity of the  
star test under perfect conditions is 1/20th wave P-V on the  
focuser  
rotation  
lock knob  
(1 of 3)  
2” accessory  
lock knob  
(1 of 3)  
Compression  
ring  
1.25” accessory adapter  
TMB Optical, Cleveland, OH 44131 E-mail: [email protected]  
ExtensionTube Installed  
Features of the Focuser’s Left Side  
© 2008 by TMB Optical  
 

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