Mewlon-250

Mewlon-250 Telescope and Specific Accessories

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The Mewlon 250 is the second instrument of Dall-Kirkham configuration manufactured by Takahashi.

The Mewton 180 had paved the way, and because of its quality had ousted its 200mm (8") competitors. Now the supremacy of Takahashi optics surpasses instruments up to 12" (300mm) aperture. As is the case with the Mewlon 180, this instrument requires no corrector plate, thus is easier to handle, is lighter than an instrument with a corrector plate, and also reaches thermal equilibrium more quickly. The curved front of the tube prevents any condensation tram entering the tube and there is no possibility of dewing as is the case with Schmidt-Cassegrains. The primary mirror has a surface accuracy of 1/20 wave, and is 1 cm over-dimensioned to avoid any possibility of vignetting. It is contained in a fixed cell, thereby avoiding any image shirt during focusing. Focusing is clone by electrically moving the secondary mirror, and the focus control box has a potentiometer to vary the rate of focusing, which is ultra smooth and can be carried out without moving the eye from the eyepiece.

This smoothness is particularly apparent in CCD imaging where accurate framing and fine smooth control is essential. The electric focus system is contained in the secondary cell, and power comes tram a 9 volt battery in the focus control panel. To achieve fast thermal balance the cover behind the mirror cell can be detached, and the cell itself is perforated with 8 circular openings. In this way, thermal equilibrium is achieve in about 40 minutes. The 15 Kg tube assembly is attached to the mounting using a dovetail system which enables rapid connection as well as coarse balance by sliding the dovetail joint before locking in place. Fine balance is obtained by sliding the magnetic 0.4 Kg counterweight (optionally 1.1 Kg) on the tube itself. To improve image contrast during planetary observation there are internal baffles in the central tube which eliminate all stray light, and the ratios of f/3 (primary) and f/4 (secondary), similar to those of the Mewlon 180, give a very stable image for such a large diameter.

The illuminated, open-centre reticle 7 x 50 finder also serves as a carrying handle, its support being moulded and rigidly attached to the main tube. Observation through the Mewlon 250 gives great satisfaction, combining light-gathering power with sharp images of high contrast, for example subtle nuances of grey can be clearly seen in the "ears" of M27 the Dumbell Nebula. With averted vision, from a dark site, it is possible to glimpse the 15th magnitude star in the centre of M57, the Ring Nebula, such is the efficiency and precision of the optics, and Enke's division can be clearly resolved in the rings of Saturn.

Coupled with an EM-200 mounting, no component weighs more than 15 Kg, making transport an easy task. The EM-200 German mounting is of high precision with a cyclic errors of under +/- 5 seconds of arc; It is a favourite for high quality photography and CCD imaging, having the facility to be manually or automatically guided. The RA and DEC drives are fully enclosed within the housing to ensure accuracy, plus total freedom from any contamination. The integral polar finder has an advanced system of alignment permitting rapid alignment to within 5' of arc of the celestial pole; The EM-200 has a precision of 3-5 times better than mass-produced fork mounts, and has a unique serial number, as does each instrument.

With individual hand figuring of the optics, to achieve the highest possible specification, the Mewlon 250 is a reference point amongst instruments of this aperture.

Technical Specfication of Mewlon-250 Telescope and Specific Accessories

Specifications may change without notice.

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