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  For additional information, select: Note #3 by Bruce Johnston

Recheck the beam's alignment with the horizontal line to make sure it still sweeps from one end to the other without straying from the line. If it strays from the horizontal line then something has moved. And the procedure must be started all over from Step 4. If it does not stray then you are now ready to check the DEC alignment.

Place the beam at the top of the vertical line and lock the RA. Sweep the beam from the top of the line to the bottom. If the beam is still on the line at the bottom then the DEC axis is perpendicular to the RA axis. If it strays to the right of the line then the right fork arm is higher than the left fork arm. If the strays to the left of the line the opposite is true. Decide which fork arm you want to raise or lower and proceed to the next step.

Step 9. Before making any adjustments it is wise to mark the original position of the fork arms by scoring the drive base with a razor where the top of each fork arm meets the drive base.

This procedure should only be done when the drive base is sitting on a level surface. Attempting to raise or lower a fork arm with the drive base mounted on the equatorial wedge will cause the arm to twist to the front or rear of the base due to the weight of the OTA.

Loosen the four bolts on the underside of the arm you want to raise or lower. Be careful when loosening these bolts, half the weight of the OTA is pushing down on this arm. Do not allow the bolts to disengage the threaded hole.

  Fig 17

Figure 17 - Score a mark to record
forkarm's original location

  Fig 18

Figure 18 - Location of four
forkarm adjustment bolts


To lower the arm loosen the bolts until you can slide the arm down buy pushing on it or tapping on it with a rubber mallet and a block of wood to protect the arm. If you choose to tap with a mallet of some type do so very gently. Remember this is a piece of precision equipment. The optics and electronics are very susceptible to vibrations.

To raise the arm, place a shim of some sort under the arm from each side. I used two cedar shims. Loosen the bolts and tap the shims with a rubber mallet to raise the arm to the desired height.

Go Back GoBack Go Forward   For more information, select: Note #3 by Bruce Johnston