| This Takahashi EM11 USD III mount has:
• Built-in Temma-2M Jr dual-axis 12VDC drive/drive corrector
• Drive corrector converts to go-to computer by adding a PC or hand control
• Low periodic error of only +/-10 arc seconds
• 250x sidereal slewing rate
• 20 pound payload capacity
• Built-in polar finder
• Variable height tripod
The Takahashi EM-11 USD III mount, Temma-2M Jr dual-axis drive/drive corrector, and FC-L tripod combination offers the amateur astronomer a well-thought-out German equatorial mount and adjustable height tripod that is simple to set up and use, light in weight and easy to transport, and perfectly adapted to the traveling amateur astronomer.
- Payload capacity: The EM-11 USD (Ultra Speed Drive) III has a maximum instrument payload capacity of 20 pounds (9kg), not including counterweights. This allows the use of most catadioptric optical tubes, along with refractors up to about 4" in aperture (such as the Takahashi TSA-102) and reflectors up to 6" or 7" in aperture (such as the Takahashi Epsilon 180). However, most astronomers will probably want to limit the instrument payload to about 14 pounds (6.5kg), the optimal payload to benefit from the increased stability of having a smaller instrument on an over-sized mount. Some optical tube examples would include the 4" aperture Takahashi TSA-102 refractor, the 3.6" TMB 92 refractor, the 6" Astro-Tech AT6RC Ritchey-Chrétien, etc.
- Drive system details: The EM-11 USD III has 144-tooth 2.9" diameter zinc drive gears in both right ascension and declination, with 14mm diameter worms (declination brass, right ascension steel(. The hardened aluminum right ascension and declination shafts are 2" in diameter and supported by multiple pre-loaded ball bearings.
The standard equipment dual axis drive motors are built into the chassis to protect them from the elements and reduce maintenance to a minimum. The quartz-controlled r. a. and dec stepper motors operate at a 100 pulse per second rate, assuring an imperceptible stepping motion during visual observing and imaging. Careful design and machining keeps the periodic error to a low +/-10 arc seconds during each 10 minute rotation of the worm gear.
The motors are powered by an optional 12 VDC source. Takahashi has an optional 110/220VAC to 12VDC power supply (#TPS0012) available, as well an optional rechargeable 12VDC battery pack (#TBAT12). The EM-11 USD III draws 0.3A when operating at the sidereal rate; 1.3A when slewing at the 250x sidereal rate; and 1.7A when first starting from a dead stop position.
The supplied hand control provides a variety of user-selected drive correction rates for astrophotography, from 0.1x sidereal to 1.9x sidereal in right ascension, and +/- 1.5 to 13.5 arc sec/sec in 1.5 arc sec/sec increments. Four pushbuttons in a diamond pattern control the motion in r. a. and dec, while a red/green LED shows which speed mode is engaged. A nearby switch and pushbuttons change the directional speed from normal/drive correction to fast slewing, change from northern to southern hemisphere operation, change the drive correction rates, etc.
The USD III control panel built into the side of the mount contains an on/off indicator; an adjustable brightness control for the internal illuminator of the built-in polar alignment scope; a computer standby switch for connecting to an optional PC or advanced Takahashi hand control (#ATHC) through the standard RS-232 port; a DC power input port; a hand control port; and an SBIG type ST4/7 autoguider port for self-guided astrophotography.
- Mount details: The EM-11 USD III’s aluminum die-cast body is built to be strong, yet light, to satisfy both stability and ease of portability needs. The complete head, including the standard equipment 7.7 pound (3.5kg) counterweight, weighs only 23.1 pounds, while the tripod weighs only 16.5 pounds, making transportation and setup easy. Additional counterweights are recommended to balance payloads over 14 pounds.
The mount is designed to operate in both northern and southern hemispheres at latitudes from 20° to 50°. A single large knob in the base of the mount adjusts the mount in altitude, while twin adjustment knobs let you fine-tune the azimuth alignment on the pole over a +/-10° arc.
The standard equipment illuminated variable-brightness polar alignment finderscope can align the scope on either celestial pole with a 5 arc minute accuracy. The alignment scale on the polar finder’s reticle is accurate through the year 2030 and can be extrapolated beyond that point. There is a built-in bubble level for leveling the mount for the most accurate tracking.
- Setting circles and slow motion controls: Right ascension and declination setting circles, used to help point the telescope at a celestial object by dialing in its coordinates, are standard equipment. The right ascension circle is marked in hours and subdivided in 10 arc minute intervals, while the declination circle is divided into four 90° quadrants, each divided into 10° segments, with each 10° segment subdivided into 2° intervals.
Large quick-release levers disengage the right ascension and declination axes independently to allow you to quickly move your optical tube manually to any part of the sky. No manual slow motion controls are provided. Once you move your OTA by hand to the vicinity of your target, the levers are reengaged and the hand control then provides motorized centering and fine-tuning of the tube position.
- Tripod: The supplied Takahashi FC-L tripod is a 16.5 pound adjustable height wood tripod with a metal accessory tray. The legs are made of a dark stained Luan mahogany. The legs extend from 36" when collapsed to a maximum extension of 59". This puts the top of the tripod between 32" and 52" above ground level, and the nodal point (the intersection of the right ascension and declination axes) between 41" and 61" above ground level. Its length makes it well suited for use with longer focal length refractors, although observing from a seated position may be necessary with some scopes.
Two hand-tighten levers on each leg lock the legs in place at the desired length. The tripod bolts onto the three mounting posts that are part of the die-cast base of the EM-11 USD III mount.
The FC-L tripod is very solid and stable, able to support the EM-11 equatorial head and its associated payloads with ease. The tripod’s wood legs have excellent vibration damping characteristics. The result is that your images remain steady and vibration-free, even at high magnifications, making for a more enjoyable observing experience.
The tripod legs are tipped with pointed metal feet, designed to sink into grass or dirt for a solid footing for your scope. A metal peg is molded into the outside of each tripod leg so you can apply pressure with your foot to anchor the scope firmly in the ground. If you set up the mount on a hard surface, such as a deck or driveway, a set of vibration damping pads would be a useful addition.
The tripod’s aluminum accessory tray helps lock the legs firmly open. A low lip on the tray keeps small items from rolling off the tray in the dark. There is a hook molded into the top of one of the legs to hold your mount’s hand control and keep it close at hand.
- Optical tube mounting method: The mount is designed primarily to be used with Takahashi tube rings, as the circular top of the mount has two holes on 35mm centers threaded to accept the M8 metric bolts supplied with Takahashi rings. However, for non-Takahashi scopes, Losmandy makes a saddle plate that mounts on the EM-11 head and holds standard Losmandy D-plate dovetails (#G11SPT).
- Computer control: The mount comes with a factory-installed Temma-2M Jr dual-axis drive/drive corrector, with built-in encoders. The Temma-2M Jr drive corrector converts to a go-to system simply by adding an optional advanced Takahashi hand control (#ATHC) or an external PC.
If you’re looking for a lightweight, very high-precision, and extremely portable mount, take a careful look at the Takahashi EM-11 USD III Temma-2M Jr mount and FC-L tripod combination.
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