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More Information  · Recommended Accessories  · Images of Some Features Price $7,500.00 Highest Useful Magnification 500x Focal Length 3000mm Focal Ratio f/12 Resolution 0.47 arc seconds Visual Limiting Magnitude 14.5 Aperture 9.8" Heaviest Single Component 33 lbs. Warranty 5 years

The Mewlon’s 260mm primary mirror is oversized compared to the scope’s effective 250mm aperture for brighter off-axis images. The primary mirror is fixed and focusing is done electrically by moving the secondary mirror fore and aft in its holder under the control of a supplied battery-operated hand control.

An optional 0.8x reducer/field flattener/corrector lens (#TMC1800) is available for the Mewlon. It converts the 250 from a 3000mm focal length f/12 system to a 2307mm focal length f/9.2. This increases the image circle from 21mm at the focal plane at f/12 to 42mm at f/9.2 with the reducer in place. The field of view is 1° using the reducer.

The well-made aluminum optical tube has a die-cast and machined metal rear cell with a removable back for faster cooling of the optics. The rear cell has both 1.25" and 2" accessory holders; a 7 x 50mm finderscope in a very robust mount that doubles as a carrying handle for the scope; and a dovetail for attaching the tube to the supplied dovetail adapter for mounting on a Takahashi EM-200 equatorial mount. The Takahashi Mewlon 250 measures 33.4" in length, 11" in diameter, and weighs 33 pounds.

Features of the Takahashi Mewlon 250 Dall-Kirkham optical tube . . .

• Dall-Kirkham Cassegrain optics: 250mm (9.8") aperture, 3000mm focal length, f/12 focal ratio, with removable rear cell and 156mm available back focus. Ellipsoidal primary mirror and spherical secondary mirror. The mirrors are coated with highly reflective enhanced aluminum and overcoated with quartz for long life.

• Fully-baffled optics: The interior of the aluminum optical tube in finished in a non-reflective matte black. The front rim of the optical tube curves inwards to form a highly effective knife-edge baffle at the front of the body. The secondary mirror light baffle is micro-grooved on its interior to shield the mirror from stray light for higher contrast. The first 20% of the primary mirror baffle tube interior is likewise micro-grooved to improve contrast. The remaining 80% of the baffle tube contains 10 knife-edge baffles machined into its interior. This combination of micro-grooves and knife-edge baffles is very effective at preventing ambient light from reaching the image plane, thereby producing the dark sky background essential for high contrast, high magnification images.

• Removable rear cell: For faster cooling of the optics when the Mewlon 250 is first taken out for an evening’s observing or imaging, the rear cell is removable. This exposes both the front and rear surfaces of the primary mirror to the air, cutting down the cooling time without having to use a battery-powered fan as is the case with many sealed optical tubes. An aluminum collar around the Cassegrain focus holds the rear cell in place. Two bat wing handles on the collar make it easy to loosen and tighten the collar to remove and later reinstall the rear cell.

• Electric focusing: Unlike many Cassegrain scopes which focus manually by turning a knob to push the primary mirror fore and aft along the central baffle tube, the Mewlon 250 focuses electrically. The primary mirror is fixed. To focus, simply touch a button on the supplied hand control to command a motor to move the secondary mirror. A premium-grade Frauhaber Swiss single linear electric motor connected to the center of the secondary mirror holder smoothly moves the secondary mirror fore and aft in tiny increments for very precise focusing. The motor/secondary mirror assembly housing is mounted in a rigid three-vane spider. Together with the fixed primary mirror and the central drive of the secondary, the rigid spider assures that the Mewlon exhibits none of the image shift typical of a conventional Cassegrain as it is focused. The battery-operated hand control plugs into a receptacle under the rear cell of the scope.

• Finderscope: A 7 x 50mm straight-through finderscope with a 6.3° field and interrupted crosshairs is standard equipment. The finderscope bracket is exceptionally robust and rigid, allowing it to be used as a carrying handle for the optical tube with little danger of knocking the finder out of collimation. An optional battery-powered red LED crosshair illuminator can be threaded into the finderscope, if desired.

• Accessory holders: Two accessory holders are supplied for use with the Mewlon 250. One is a 2" accessory holder that threads onto the rear cell of the scope and can be used with a 2" star diagonal or 2" photo accessories. It has two thumbscrews to hold accessories firmly in place. The second slips into the 2" adapter and holds optional 1.25" accessories (star diagonal, camera adapter, terrestrial image erecting diagonal, etc.) It uses a compression ring to hold accessories.

• Mounting dovetail: The Mewlon 250 has an attached hexagonal dovetail plate for mounting the scope quickly and directly onto the supplied dovetail adapter. The dovetail adapter fits the Takahashi EM-200 equatorial mount, the recommended mount for use with this scope, although the dovetail adapter can itself be adapted to non-Takahashi mounts.

• Counterweight: Because the fixed location of the Mewlon 250 dovetail plate makes it difficult to balance varying accessory loads when the scope is installed on an EM-200 mount, a counterweight system is built into the scope. This consists of a steel rail mounted under the optical tube. A 14 ounce (0.4 kg) counterweight with a powerful built-in magnet fits onto the rail. The magnet holds the counterweight in place, but allows it to be moved fore and aft on the rail to balance differing accessory loads. A thumbscrew locks the counterweight in place on the rail once the proper balance has been found.