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Changing TELESCOPES to GOTO operation


Most telescope mounts can be converted to modern standards capable of GOTO operation if required. This is necessary to take advantage of modern technology for digital photography amongst other uses. It is now possible to take pictures with a quality only dreamed of ten years ago. The motor drives must be of similar high quality.

AWR can motorize virtually any equatorially mounted telescope. We can convert many mount types or offer solutions to cater for telescopes with size range 6 inch to 36 inch aperture range. We have motorised many telescopes on robust mechanical mounts, ranging in age from Victorian to the modern day. These include all types of homemade and commercial products. The mount must have slow motions that are smooth without jerks or tight spots. The more even the torque requirement is the more even the running will be, and better if this torque is low, normally less than 50Ncm. Don't worry if there are no slow motions, we can fit worm wheel sets provided you have decent quality axles to put them on!

All GEARED reductions can have the drive rate exactly calculated before hand and so it is possible to fit any type of AWR drive units, Intelligent or non-intelligent. All will have extremely fine step sizes and so vibration is non-existant. The most comprehensive feature set is available to ALL of these mounts giving you the opportunity to get the best out of your astronomy.

Teslescope upgrades for SCHOOLS (please read associated page).

GERMAN EQUATORIAL MOUNTS
This is the solution found on small telescopes. You have a counterbalance on the DEC axis and the two axes are tilted over so that rotating one axis (the RA asxis) it follows the stars. The equatorial head needs to be heavy bacause it must not wobble in the breeze. GEM mounts are found carrying Newtonian telescopes up to 12 inch aperture. Beyond that the mount needs to be very heavy and becomes unwieldy. All the AWR GOTO kits for commercial telescopes convert this type of mount. The ALTER D6 weighs in at 82kg including the tripod. The smaller modern standard mounts supported by an upgrade kit are Alter D6, EQ5, CG5, CGE, SP, DX, GP-DX, GPE, HEQ5, EQ6.

Famous name mounts which we have converted with brackets similar to this are Beacon Hill Telescopes (any worm size), Fullerscopes Mk 4, Astronomical Equipment (Luton), Astro Promotions (Rob Miller), Calver, Browning etc amongst the recognisable makes. See the MOTORS page for more ideas of brackets.

The internal mechanics have worm and wheel reductions in the ratio 100:1 up to 360:1 and so the slow motion axis can be turned easily by motors, usually with other gearboxes, to get the slow running required There is an art to getting the mechanics to run smoothly enough and there we can help. There are many pages describing BACKLASH, BALANCE, PERIODIC ERROR within our web pages. You can find these topics by using the KEYWORD INDEX of keywords and phrases.

COMPOUND WORM & WHEEL ASSEMBLIES
In the age of clockwork drives there are some Victorian mounts that were designed to have a compound drive on the RA axis. A large worm and wheel was driven by clockwork (probably converted to synchronous motor drive by now). This wheel was connected by clutch to a secondary worm and wheel which could be operated by hand - slow motion guiding correction. The whole assembly then turned the telescope. The modern solution is to just drive the large worm and wheel using our large microstepping motors. We did just this adaption for SHREWSBURY SCHOOL.

FORK MOUNTS
There are small commercial telescopes on fork mounts - MEADE and CELESTRON - offering Schmidt Cassegrain style optics (short stubby tubes) and these lend themselcves to the small fork mount. It is possible for us to convert the mechanics of these to GOTO if it is not this type already but in many cases the cheaper otption is to take the Tube Assembly and put it on an Equatorial mount (such as an EQ5). See the LX200 refurbishment in detail.

Large commercial Fork mounts are made by Beacon Hill Telescopes. These are robust with huge worm and wheel sets up to 14 inch diameter. Once you have the worm reductions then the mount can be driven by fitting brackets for the motors and perhaps another gear stage reduction of 3:1 AWR work with several suppliers to provide complete solutions for new telescopes. We can retrofit existing telescopes. See the Guildford Astro Soc 0.5 metre.

FRICTION DRIVE MOUNTS
An alternative way of providing the slow motions is by several stages of friction reduction. There are many excellent telescopes with this arrangement. They do not suffer from backlash. The drive must provide extremely smooth operation with adjustable acceleration and deceleration so that the discs do not slip. AWR microstep drives have this property and have been fitted to a fair range of different telescopes using this reduction method. The intelligent handset allows entry of non-integer reduction ratios, essential for this type of drive.

TANGENT ARM or SECTOR PLATE
These mechanical solutions provide a small angle of movement which has traditionally been used for small adjustments after a manual movement. These type of drives can be converted to useful GOTO arrangements. If a bright star can be located near to the object of interest then the Intelligent drive system can synchronise onto these coordinates and then the small offset to the required object is done by GOTO. If digital encoders are fitted then the job is easier, we have a solution to readout the position in RA and DEC coordinates. The intelligent handset allows entry of non-integer reduction ratios, essential for this type of drive.

CHAIN DRIVES
There is one telescope we have converted successfully to GOTO operation with a CHAIN drive as the primary reduction. It is the 24 inch reflector belonging to the Hampshire Astronomical group. There were no specific problems. The reduction ratio needed tweaked but a 24 volt system gave it slewing ability of over a degree per second.

AWR SOLUTIONS
AWR items suitable for the largest and heaviest telescopes are the Microstep systems using a Sanyo Denki rare earth stepper motor (AWR part number MOTOR/210) with slew performance normally 0.5 degree per second but extended to 3 degrees per second with the right power supply & design (expensive!). The equipment you will need includes two motors, motor brackets, mechanical motion components, Intelligent Handset or Simple handset and a power supply. Normal power supply requirements are 12V DC at 8.5 amps, but could be 12V at 2.5 amps, 24V at 8.5 amps etc. A computer with serial IH-PC lead provides point and click GOTO's if you do not want to rely on the Intelligent Handset. Typical GOTO system prices are in the range 750 to 1,200 depending on what is required. NON-GOTO solutions are from 450.

Non-GOTO solutions arebased on the Microstep drivebox, microstepping motors and a simple handset. At a later date these can be computerised by either direct connection to the drivebox or through the Intelligent Handset.

Design of the correct solution is essential to get the best compromise of speed and power so we tailor each design to your specific requirements. This work continues through after sale service during the commissioning period. Deviations from the standard kit are possible - one system used a 40 Volt 350 Watt power supply with 3 amp per phase motors. We have the knowledge to know what works and what doesn't because of the experiences of many successful installations of telescopes in this category. Reduction ratio's at least 600:1 are recommended giving approx 100 microsteps per second for sidereal rate.

Difficult telescopes of a Heritage nature can be upgraded discreetly just by adding Professional Digital Setting Circles. See our work at the Science Centre, Herstmonceux on all the telescops of the Equatorial Group.

THE NEXT STEP
Decide on the type of system you want by virtue of the features you require. Allow growing room as the equipment will last many years. User support keeps it up to date and with occasional service it should still be going 20+ years time.

The motor needs to be matched to your drive so that it has at least twice the anticipated torque required. There are ways descibed for measuring the required torque in odd topics page. Then it will not lose steps and will perform to the maximum slew rate. We will know this in advance given the total drive reduction ratios present. At this stage depending on your requirements we may advise on a 24 Volt system to meet the slew performance required. A suggestion for the motor bracket and further gear / pulley reductions will complete the equipment list. There are plenty of accessories in our catalogue to make life easier and the star tracking better.

Please ask AWR if there are items you are unsure about. We can quote you for a standard package or for further customising.

August 2007 AWR Technology HOME PAGE www.awrtech.co.uk