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-
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
TMB Optical TMB-92
Thomas M. Back Signature Series
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
Next, moisten a ball of USP grade pure cotton with a few drops of a
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
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
However, TMB objectives are corrected at the peak visual wavelength centered around 560nm in 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
A FINAL WORD
Thank you for your purchase of our
Congratulations on your purchase of this TMB Optical TMB- 92 Signature Series
At only 13.25” in length, the
The
PHOTO/VISUAL CONFIGURATIONS
The
a 2.25” extension tube that can be in- stalled between the optical tube and the focuser for visual use.
When the optical tube and focuser are assembled without the extension tube, the resulting physically short tele- scope configuration provides the long back focus needed by those primarily
focuser rotation.
The supplied carrying case is precut to hold the
FOCUSER
Your
The 2” accessory adapter is secured to the focuser drawtube by three recessed
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
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
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
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
No optic is perfect, and every brand and model scope will show some error in an extended star test. The sensitivity of the
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!
Aperture | BRIEF SPECIFICATIONS | ||
|
| 92mm (3.6”) | |
Focal Length |
| 506mm | |
Focal Ratio |
| f/5.5 | |
Objective Type | ...................... | ||
| with an | ||
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; 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) |
interested in serious CCD imaging us-
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
For those primarily interested in visual observing and only casual imaging with a 35mm camera, webcam, or Deep Sky
at the opposite end of the extension tube now lock the focuser in place and allow focuser rotation, just as the large brass lock knobs in the op- tical tube do when the extension tube is
Retracted
lens shade
Left coarse
focus knob
Compression
ring
Focuser rotation/extension tube
lock knob (1 of 3)
2.25” visual extension tube installs here
Hex head
screw
attaching 2”
adapter to
drawtube (2 of 3)
1.25”
accessory lock knob
2”
accessory
adapter
star test under perfect conditions is 1/20th wave
Case Dimensions | 22.25” x 12.75” x 8” |
not used. A Teflon insert in the focuser
| 2” accessory | Compression |
| lock knob | ring |
1.25” accessory adapter | (1 of 3) |
|
TMB Optical, Cleveland, OH 44131
© 2008 by TMB Optical
end of the extension tube assures smooth