Takahashi - Mewlon 250 10" Dall-Kirkham Telescope on EM-200 III Mount

The Mewlon Series of Dall-Kirkham Telescopes by Takahashi© combines refractor-like performance in
a larger folded optic reflector design.

The EM-200 mount provides a stable, accurate platform for the M-250. The integral polar alignment
telescope and R.A. axis level make accurate polar alignment to within 2 arc minutes of the
celestial pole quick and easy. The reticle is designed to be used in either Hemisphere until the
year 2030. No other manufacturer uses such a highly accurate polar telescope.

The Mewlon series of Dall-Kirkham Cassegrain telescopes from Takahashi offer the experienced
observer a level of performance and portability not found in other Cassegrain telescopes mass
produced for amateurs. Classical Cassegrain telescopes offer excellent performance but they are
extremely expensive to produce at large apertures. By concentrating on the Dall-Kirkham
Cassegrains, the Mewlon offers a professional level of performance within reach of most
amateurs.

The Mewlons use an ellipsoidal figure on the primary mirror and a spherical figure on the
secondary. By focusing on very tight tolerances for these surfaces, Takahashi is able to deliver
a compact telescope with reasonable aperture and high resolution. Where fast F/ratios are not
required, the F/12 Mewlons provide excellent contrast by utilizing a smaller secondary mirror
than comparable Cassegrain designs. Secondary obstruction as a percentage of diameter is 29-31%
on the Mewlons. Classical Cassegrain telescopes usually have secondary obstruction of 32% or
greater. Commercial Schmidt-Cassegrains have secondary obstructions of approximately 38% for F/10
systems. Ritchey-Chretien Cassegrains have even more secondary obstruction making them less
suitable for visual, high contrast applications.

Takahashi uses extensive knife-edge baffling to minimize stray reflections as well as a specially
designed tube that also acts as a light baffle. The result is an instrument that rivals an
excellent long-focus Newtonian or refractor for contrast and sharpness. Some opticians have
criticized the Dall-Kirkham design as having unacceptable coma. With most eyepieces (including
Panoptics & Naglers) the coma is negligible and well outside the field of view. Stars are much
smaller and sharper than in commercial Schmidt-Cassegrains. Coma may be a problem for wide-field
astro-imaging, but these instruments were not designed for such tasks. With Takahashi’s field
flattener/reducer, these instruments offer superb off-axis images at F/9.

The 250mm and 300mm models have electronic focusing accomplished by moving the secondary mirror.
This eliminates the image-shift problem inherent to commercial Schmidt-Cassegrains with moving
primary mirrors. Because of the loose tolerances required in moving large and heavy mirrors on a
baffle tube, most SCT’s will not maintain perfect collimation. Image quality is then compromised
in such optical systems. The large Mewlons also have removable covers for their primary mirror
cells, this aides in rapid mirror cooling so that the observer can take advantage of favorable
seeing conditions more quickly. These features make the large Mewlons ideal for high-resolution
CCD imagery.

With the Mewlon series, one doesn’t have to sacrifice optical performance for high portability.
The Mewlon 250 weighs only 28lbs (12.7kg) and is remarkably compact for a 10” Cassegrain. This
instrument is highly portable and offers deep sky views that are exceptional. On the planets,
many observers have reported seeing details they thought impossible with telescopes of this
aperture. With the exception of a few diffraction spikes around bright stars, on might believe
they were observing with a large apochromatic refractor. The advantage, though, is a greater
amount of light grasp and resolution than a comparably priced refractor. Indeed, the Mewlons
offer an exceptional value in their aperture class.

So if you desire a professional grade instrument in a compact, lightweight package or are tired
of compromising light grasp for crisp detail and contrast, check out the Mewlon Cassegrains by
Takahashi. You will be pleasantly surprised by their performance.

    * The Mewlon combines refractor-like performance in a larger folded optic reflector design.
       
    * The 250 has 10” of aperture and a focal ratio of 12.
       
    * Comes with Fraulhaber German electric focus motor for secondary (no image shift!) 

Mewlon-250US System comes with:

    * EM-200 USDIII Mount,
    * SE-L Tripod,
    * 7X50 finder with dovetail,
    * Tube weight,
    * Two 5kg counterweights,
    * Hand controller
    * Power cable. 

Takahashi EM-200 USDIII Mount

The EM-200 USD III is an accurate, precision-built German equatorial mount that provides a stable
platform for payloads of up to 40 pounds. It is an ideal mount for any type telescope, be it a
refractor, reflector, or cassegrain.

The modern aesthetic design of the EM-200 is highly attractive as well as beautifully functional.
The RA and DEC stepper motors are fully integrated into the mounting,and the high precision design
and construction provides cyclic errors lower than +/- 5 arc seconds.

The integrated polar alignment telescope has an illuminated reticule which can be dimmed to suit
the user or observing conditions. In conjunction with the precision altitude and azimuth
adjusters, this will typically give polar alignment accuracy within 2 minutes of arc of the
celestial pole.

Improvements (EM-200 vs EM-200 USD III) include the ability for operation on 12v (manual
operation via hand controller or remote operation with Temma upgrade and a PC) or 24v (remote
operation via a PC with the addition of the Temma upgrade). These new mounts feature high speed
slewing at 300x [sidereal rate] at 12v and 700x at 24v. A hand controller and power cable for
12V/220V battery connection is included.

Specifications for the Takahashi EM-200 Mount

    * R.A. Slow Motion: Motor Driven
    * DEC Slow Motion: Motor Driven
    * Azimuth Adjustment: 30º
    * Elevation: 0-50º or 5-50º
    * Setting Circles: R.A> -10’ increments, DEC, -2º increments
    * Tracking Accuracy: 5 arc seconds
    * Load Capacity: 35.2 lbs. (16kg)
    * Gross Weight, including Counterweight: 56.2 lbs (25.5kg)
    * Counterweights: 2 - 5kg
    * Polar Finder: Built-in with 5’ setting accuracy, scale pattern effective til 2015 with
quick reference dial for N/S
    * Motor Drive: Sidereal rate N/S switching
    * Slewing Speed R.A.: 0.05x--2x
    * Slewing Speed R.A. High Speed Mode: 2X - 16X
    * Slewing Speed DEC: 0-15 arc/sec
    * Slewing Speed DEC High Speed Mode: 30-240 arc/sec 

SPECIFICATIONS for the M-210 (Tube assembly only)

Effective aperture 250mm
Focal length 3000mm/2307mm w/reducer
Focal ratio F/12-F/9.2 w/reducer
Resolution 0.46”
Limiting magnitude 13.8
Light grasp 1275x
Image circle ø21mm/ø42mm w/reducer
Photographic field 1.0° w/reducer
Total length of main tube 850mm
Diameter of main tube ø280mm
Primary mirror 260mm F/3
Secondary mirror 72mm /X4
Secondary Obstruction 29%
Finder scope 7x50 6.3°
Gross wt. of main tube assembly 12.5kg (27.5lbs)