Takahashi - Mewlon 300 12 inch Dall-Kirkham on EM-500 Mount with SQ-LL Pier

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 aids 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

Mewlon 300 - 12” f/11.9 Dall-Kirkham on EM-500 Mount w/SQ-LL PIER Includes:

    * Takahashi Mewlon 300 Optical Tube Assembly
    * Tube Holder
    * 11X70 Finder
    * Double Finder Bracket
    * Tube Weight
    * Diagonal
    * 30mm LE 1.25\” Eyepiece
    * EM-500 Temma II Equatorial Mount
    * SQ-LL Pier
    * Dual-Axis Hand controller
    * Illuminated Polar Finder
    * Cables
    * Software 
    * The 300 has 11.8\” of aperture and a focal ratio of 11.9.       
    * This system comes with the EM-500 mount and Takahashi\’s SQ-LL Pier.       
    * The OTA comes with Fraulhaber German electric focus motor for secondary (no image shift!) 

Takahashi EM-500 Temma II Mount

The state-of-the-art EM-500 Temma II mount has a tracking accuracy that is guaranteed to +/- 3.5
arc seconds without periodic error correction and it runs off of 24V DC. The EM-500 Temma II
slews at 560X the Sidereal rate. The Temma II GoTo System can be operated via The Sky, Level IV
software and is closed-loop. This means that the telescope can be moved manually without
restarting the GoTo system. The mount can also be operated in manual (non-GoTo) mode without
connecting to a computer and dual-axis tracking is available in this mode.

The self-contained illuminated polar finder is accurate to two arc minutes of the pole.
Autoguider and CCD cables are available for most CCD cameras including serial, RJ-11, and USB
connectors. Main gears are phosphor-bronze with matching poly-steel worms for greater accuracy
and durability vs. aluminum & stainless steel. New, precision micro-stepping motors provide high
durabilty with softer pulse-peaks for better imaging. No need for servos and variable-voltage
systems that reduce longevity.

    * Type: German type, Dual-Axis Drive
    * R.A. Slow Motion: Electric
    * DEC Slow Motion: Electric
    * Self-contained illuminated polar finder: Accurate to two arc minutes of the pole
    * Operation: 12V/24v
    * Slewing speed: 520x sidereal @ 24v
    * Mount Worm Screw Period: 10 Minutes
    * Input Terminal: For Auto Guider (ST-4)
    * Loading Capacity: 40kg. (89lbs.) but it can reasonably handle 120lbs.
    * Tracking Accuracy: +/-3.5\”
    * Operational software: The Sky, Level IV software and is closed-loop 

SPECIFICATIONS for the M-300 (Tube assembly only)

Effective aperture 300mm
Focal length 3572mm/2739mm w/reducer
Focal ratio F/11.9-F/9.1 w/reducer
Resolution 0.40”
Limiting magnitude 14.2
Light grasp 1837x
Image circle ø25mm/ø42mm w/reducer
Photographic field 45\’ w/reducer
Total length of main tube 1094mm
Diameter of main tube ø324mm
Primary mirror 310mm F/3
Secondary mirror 95mm /X4
Secondary Obstruction  29%
Finder scope 11x70 4.2°
Gross wt. of main tube assembly 26kg (57.2lbs)