The Mewlon telescopes made by Takahashi combine refractor-like performance in a large folded optic reflector design. This scope has a focal length of 3000mm, and a focal ratio of f12. This telescope is a Cassegrain type design, but uses no corrector lens. The Dall-Kirkham design uses an objective mirror with a concave elliptical surface. The primary is a 260mm diameter f3 mirror. The secondary is a spherical convex 72mm/x4 mirror. I have a reducer that provides a focal ratio of f9.2 and an effective focal length of 2307mm
This 10-inch version of the Takahashi Mewlon scopes has a fixed main mirror and uses an electric focuser to move the secondary. A cable plugs into the rear of the scope for the purpose of operating the electric focuser. The standard Takahasi control box for operating the Mewlon 250 electric focuser uses a 9-volt battery, so it is important to always carry a spare battery. If the battery fails, there is no other way on the standard Mewlon 250 to adjust the focus, and your night of observing may come to an end. However, I have two modifications that get around this limitation. My Mewlon 250 includes the optional Takahashi focuser for cassegrains that screws into the back of the optical tube assembly, which allows for manual focusing within a limited range. Also, I have the ALLOS motorized focuser controller made by FILOS. It operates from the same 24-volt power supply that powers the Temma mount, and eliminates dependence upon a 9-volt battery. Using an ASCOM software driver, it allows the electric focuser to be computer controlled. The ALLOS controller further provides a wide range of focusing speeds, including ultra slow speed focusing. The ALLOS controller does not require any modification to the Mewlon 250. It has a control box that includes a port for plugging in a guide cable to control a Temma mount, in addition to the RS-232 cable that connects to a computer serial port. The Takahashi focuser for cassegrains includes a camera angle adjuster. It works with the Takahashi CN-212, Mewlon 210, and Mewlon 180 as well.
The photos on this page show the Mewlon 250 with an ST-8XE CCD attached. The photo immediately above shows a good view of the optional Takahashi focuser for cassegrains (part number TCF0121). These photos were taken during morning twlight after a night of imaging with the ST-8XE.
The finder scope is securely attached to the optical tube assembly, and may be used as a convenient handle for carrying the scope. The optical tude assembly weighes 12.5 kilograms, and is easy to handle and set up.
I use the Mewlon 250 telescope for small objects that benefit from a long focal length. This scope is especially useful for imaging planetary nebulae. A Takahashi NJP Temma mount is used to support the optical tube assembly when doing CCD imaging.
Complete list of images
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