ASTRO-PHYSICS 1200 Manuel - Page 7

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telescope or JMI digital setting circles, then tweak the final polar alignment by star drifting. Please refer to the

recommended reading list at the end of this manual.

2. Loosen the two altitude locking knobs and the four pier knobs. Refer back to the section on Altitude and Azimuth

Adjustments – Rough Polar Alignment

3. Follow one of the methods of polar alignment mentioned above.

4. When polar alignment has been achieved, tighten the two altitude locking knobs and the four pier knobs. Please

note that the polar axis pivot screws should have been tight throughout the fine polar alignment process.

OPERATION OF THE MOUNTING

R.A. and Dec. Damper knobs

The R.A. and Dec. damper knobs are not intended as axis locks. They should be tightened with light finger pressure, so

that a slight resistance can be felt when pushing an unclutched axis by hand. This really adds to the "feel" at the end of

the scope with the drives adjusted correctly.

R.A. and Dec. Clutch knobs

1. What do they do?

The three R.A. and three Dec. clutch knobs depicted in the diagram on page 2 have the function of connecting the

R.A. and Dec. axes to their respective drive worm wheel gears. Their function is progressive, from no tension (axes

free to move – as required during correct balancing of the telescope) to a completely "locked up" state.

2. How can you find out what they really do?

As shipped, all 1200 mounts have all three R.A. and Dec. clutch knobs firmly hand tightened. This will give you a

good idea of the maximum tightness (clutch action) than can be achieved by hand effort alone. At this point, you

must bear in mind that for optimum performance all three clutch knobs on each axis (R.A. or Dec.) should be

tightened evenly with the same tension i.e. all three half tight, all three fully tight, etc.

In order to feel the effect of the clutch knobs, you may wish to partially assemble your mount. Fit together the R.A.

and Dec. assemblies plus mounting plate and counterweight shaft. Do not put scope and counterweights on at this

stage. With the above assembly (with the clutch knobs firmly hand tightened – "as shipped"), you can feel the

amount of force needed to move each axis by hand. Grab each ends of the telescope mounting plate and move it

with a backward and forward movement of the Dec. axis. You will feel considerable resistance to this motion.

Perform the same operation on the R.A. axis by moving the counterweight shaft backward and forward. With a

well-balanced telescope, the above tightness of the clutch knobs will be sufficient for all normal conditions of use.

Now, if you proceed to mount up and balance your telescope, you can "feel" what this resistance in R.A. and Dec.

(movement backwards and forwards) is like when you make these motions from the eyepiece end of your telescope

as you would during normal use when slewing (pushing) by hand to acquire an astronomical object within the field

of view of your finder or scope

3. How tight can the clutch be and can you do any damage by pushing against them?

The maximum tightness of this clutch system is ½ turn (with a 5/32 allen key) further in than the tension you can

achieve with the knobs by hand. You will see that each clutch knob has a 5/32 hex socket for tightening with an

allen key. With this extra ½ turn on each clutch knob, the axis (axes) will be considered completely "locked up" and

you should not attempt to push your scope by hand against this "locked up" resistance, or undue stress will be

placed on the worm wheel/worm and bearings.

However, if you are undertaking a very long astrophoto exposure, it is advisable to increase the pressure on each

clutch knob (with the 5/32 key) by about 1/4

hand with this tension, however you will notice considerably more effort is required to achieve movement. This is

the absolute maximum tension that can be used for hand slewing. As a general rule, if you have a big scope (7" or

8" refractor) with all the accessories, you will need more clutch tension than a 5" or 6" scope.

Drive Test Knobs - You will notice in diagram 7 below the R.A. and Dec. drive test handles. These are NOT intended as

manual control knobs for centering objects in the field of view. Please use the buttons of the dual axis hand controller to

center objects in the eyepiece. Never, never attempt to turn these knobs manually.

turn on Dec. and 1/8

- 7 -

turn on R.A. You may safely slew the scope by