Ultimate Newtonian Telescope Rotating Head

The Rotating Head

Description and Adjustment

The rotating head is a new design that allows the user to easily and smoothly turn the eyepiece to a convenient observing position. How this design works and how the head is adjusted is explained below

This is a cross-sectional representation of the ring system. The rings are located on the outside of the tube and are a nested pair made of machined aluminum . The basic concept is simple, the outer ring contains eight delrin screws each having a end point formed at a 45 degree angle. These individually adjusted pointed heads bear directly into a similarly formed and matching groove cut into the inner ring and create a self-aligning, self-centering rotating surface. Motion is smooth because Delrin is a somewhat self-lubricating material and this is assisted by a small amount of oil wiped into the aluminum groove.

Each delrin screw is adjusted using a screwdriver. Make certain that the screwdriver head is smaller that the screw hole or you may ruin the threads. The screws turn very easily but remain in place. Never tighten them hard or even near hard, just a gentle touch against the inner grove ring is sufficient.

The inner ring is shown here.

The outer ring is shown here. Note the eight adjustment screw holes in the ring perimeter.

The above pictures show the condition of the rings when they are first placed upon each other prior to properly adjusting the screws. Note that there is no space between the rings. The left picture shows the upper ring improperly offset to the left. The right picture shows the upper ring skewed a little to the right. Both rings must be exactly centered with respect to each other.

The picture at the left shows the rings properly oriented. Use a straight edge of some kind, as seen at the right, to align the edges. Exactly how this procedure is used will be explained below.

A properly aligned and adjusted set of rings. Note that not only are the edges exactly aligned but there is a 0.050" space between the rings. This space emerges naturally when the delrin screws are properly adjusted and allows for smooth and free rotation.

Instructions for Adjustment

Set the telescope on its bottom end on a hard level surface. Crank in the focuser and remove any eyepieces. Begin by backing off all eight delrin screws until they are loose. If fitting the head for the first time back the screws off so the that the head can be easily placed over the lower ring. If you are re-adjusting the screws, back all screws off until the upper ring is loose. If things get out of whack you must start from scratch. Never force anything. The inner grooved ring must be round and free of dents and dings or the screw points will hang up and stick.

There are eight screws. The drawing above shows how they are numbered for reference purposes. The rectangle at the right surrounding the number 1 represents the focuser and is to be used as a reference. Only four of these screws, at opposite and right angles, (nos. 1, 3, 5 and 7) will be used for primary adjustment. Think of these as the primary screws. Back the other secondary screws (nos. 2, 4, 6 and 8) out so they do not touch the inner ring. I suggest pointing the focuser in line with the number 1 screw and using that as the prime reference screw. This allows you to keep track of things.

Tighten number 1 screw until the outer faces of the two rings are approximately even, then go to the screw directly in the rear and tighten that one until the rings separate a little, but do not tighten fully. Now, go to a screw 3 at 90 degrees (half way between the front and back screw) and tighten that until the faces are even, then go to the screw directly opposite, number 7, and tighten that one until the rings separate a little, but do not tighten fully. The two rings should now be separated, not perhaps evenly, but separated. Try and rotate the top. It should rotate but will likely wobble. Go back to screws 1 and 5 and tighten or loosen those until the faces are even and aligned when a straight edge is placed against them at the screw locations and the top rotates with a bit of friction but rotates easily. Then go back to screws 3 and 7 and tighten those until the faces are even and aligned at the screw positions when a straight edge is placed against them and the top rotates with a bit of friction but rotates easily.

The top should now rotate fairly well but perhaps not perfectly. Go to each of the four primary screws you just worked on, 1, 3, 5 and 7, and take your forefinger and thumb and squeeze the rings together and the screw locations and see if the rings compress. If they do, the screws in that direction may be a little bit loose - tighten one just a very little and see if you can still turn the head. Do this to all four prime adjustment screws until the motion is really nice and smooth and the friction is even. Remember to keep checking to see that the faces of the upper and lower rings are even. If they are not the two rings will not be truly concentric and may bind.

Now, go to each of the secondary screws in order and tighten them one at a time until the screw just touches but does not cause friction to increase. This stabilizes the head and imparts a lot of additional support.

If you lose track of what you are doing, go back to the beginning - that's what I do. You cannot just indiscriminately tighten screws - you will get nowhere and become frustrated. A logical system must be applied. This may take a little practice but after a couple of trials, you'll get it. It takes me about five minutes to set and adjust a head.