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Telescope Mount 1

Copyright 2004

Help us develop our process to build Moon terrain maps in 3D

Simple Equatorial Telescope Mount with Setting Circles

-- Freebie

By Tom Riley of Baltimore, MD.

Woodware Designs, Woodware@woodwaredesigns.com

Sometimes what you need is a quick telescope mount that you can make from readily available, inexpensive materials in one weekend. No fancy machined parts. No mail order stuff that takes two weeks to not get there. Just go down to the local home center, buy a few things, scrounge some scrap materials, and build it today.

This design is well within the capability of high school students. It folds up to go in a car trunk and it can handle a 6 or 8 inch Newtonian scope.

In apparatus is smooth moving and low to the ground. I built one of these mounts in the 1970's and used it for several years. I am now writing it up from memory.

If you buy the parts new the cost will be about $75.00. Painted up nice, this mount will looks real good with a flared curve on the sides.

You can even add setting circles. My reference for the circles is all about Telescopes by Sam Brown (Edmund Scientific Co., New Jersey 1979).

This free design includes six detailed sketches. Three bit map pictures are included in the text but these can be a little fuzzy. You can clear drawings by e-mailing us this little form.


You can make this mount by:

  1. Downloading the drawings and this text.
  2. Studying this information and locating the materials.
  3. Cutting and drilling the wooden pieces.
  4. Hand lapping the pipe joints
  5. Custom fitting the shelf length to suit your longitude
  6. Making the setting circles
  7. Finishing all wood pieces
  8. Assembling the mount.
  1. Discussion of Sketches

    After you download the sketches, these notes will help you understand them more completely.

    1. Simple Equatorial Telescope Mount (above)

      The front view and side view show the Simple Equatorial Telescope Mount with its two sides spread wide in a 'V'. The point of the 'V' holds a piece of pipe that serves as the mechanical apparatus for the mount. The telescope shown in a six inch Newtonian.

      Telescope Mount 2
    2. Simple Equatorial Telescope Mount, Top View, Sketch #2

      This sketch is shows top view. The wide wing sides that form a stable tripod for the scope. The telescope is counter weighted with loose weights borrowed from a small dumb bell.

      Telescope Mount 3
    3. Simple Equatorial Telescope Mount, Wooden Parts, Sketch #3

      This sketch shows the wooden parts of the mount. The hardware parts are listed in the parts list below. Two sides are needed. They form a pair as the two beveled edges should both slope to the center. The oval holes in the sides are handles.

    4. Simple Equatorial Telescope Mount, Setting Circles, Sketch #4

      This shows the parts for the setting circles and also includes the full size pointer.

    5. Simple Equatorial Telescope Mount, Ascension Setting Circle, Sketch #5

      This is the full size ascension setting circle that mounts on the base. You can use either the 4 inch circle for the 5.5 inch circle. The outer ring of numbers are the 24 hours of the day. The inner circle show 1 to 6 hour for relative readings. The smallest marks are five minutes.

    6. Simple Equatorial Telescope Mount, Declination Setting Circle, Sketch #5

      This is the full size declination setting circle that mounts on the scope holder. You can use either the 4 inch circle for the 5.5 inch circle. The smallest marks on the outer circle are 1 degree, on the inner circle they are 2 degrees.


  2. Materials

    This mount is made from a pieces of 3/4 inch plywood, bits of wood, and some pieces of pipe. The parts are assembled with glue, wood screws. and pipe clamps.

    1. Wood

      Sheet Goods:

      • 1 -- Fir Plywood, .75 in., A/C, 4x4 feet, -- $16.00
      • 1 -- Masonite, 1/8 inch, 2 x 2 ft ---------- $4.00

      You might have to buy an entire 4 by 8 sheet or you might be able to salvage thinner scrap plywood and glue up double thicknesses. The masonite can come from an old piece of cheap furniture.

      Molding:
      • 18 in. -- Pine, 1.5 by .75 inches, $.50/ft -- $ 1.50

      This is best cut from hardwood scrap.

      Wood Subtotal: $21.50
    2. Hardware
      • 6 -- Screw, flat head, #8 1.25 inch -- $ .75
      • 4 -- 1/4 inch by 2 inch bolts -- $ .50
      • 8 -- 1/4 inch flat washers - $ .25
      • 4 -- 1/4 inch wing nuts -- $ .50
      • 4 -- #10 x 1 in. flat head screw -- $ .50
      • 8 oz. -- Woodworker's Glue -- $ 3.80
      • 4 -- 1.5 in. Pipe Clamps -- $6.00
      • 1 -- 1.25 in. Dia, by 20 inch pipe nipple -- $ 6.00
      • 1 -- 1.25 in. Dia. pipe 'T' -- $ 3.50
      • 1 -- 1.25 in. to .75 in. adapter -- $ 1.50
      • 1 -- .75 in. by 8 inch pipe nipple -- $ 3.00
      • 1 -- .75 in. pipe cap -- $ 1.50
      • 1 -- 1.25 inch short nipple -- $ 2.00
      • 1 -- 1.25 inch flange -- $ 3.00
      • 1 tube -- Lapping Compound -- $2.50
      • 2 -- Large hose clamps -- $ 5.00

      Hardware Subtotal: $40.30

    3. Finish:
      • 1 qt. -- Paint, oil based -- $ 7.00

      Finish Subtotal: $ 7.00

    4. Omissions and Contingencies (~8%) ( Tax, sand paper, etc.) $6.20
    5. Estimate Total Cost $75

    This is only an estimate (made in the March 1999). You can save a lot of money if you use a lot of scrap wood. In fact, there is not reason all the wood parts cannot be made form old pallets and plywood shipping boxes. If you have thin plywood then glue together two pieces face-to-face.

  3. Tools

    This Mount was designed to be build using a few simple tool.

    1. Electric Drill, 3/8 chuck
    2. Screw Mate bit for #8 screws -- $6.20 new
    3. Jig saw, skill, saw or access to table or radial arm saw
    4. Punch and hammer
    5. Square
    6. Screw drivers

    You will also need sand paper, paint brushes. etc. It would be nice to have a four-in-hand rasp.


  4. Building Your Mount

    This is your mount and you can build it to suit your likes and needs. After all that is why you build your own stuff anyway.

    1. Options

      You need to decide on these options before you build the mount.

      1. Longitude Adjustment

        The main axis must have the same angle as your latitude for a true equatorial mount. The unit shown is for Baltimore Maryland at 39 degrees north latitude. With this design, you have a fair amount of adjustment capable by adjusting the spread of the sides. The central shelf sets this spread.

        If you live at a significantly different latitude then you may need to adjust the angle cut on the side panels. This angle (shown 30 degrees) should be about 10 degrees less than your latitude. If you are in doubt then cut a scale model out of cardboard and try different angles.

      2. Setting Circles

        The setting circles take a bit of fiddling to get them to work right but they do teach you a lot about how setting circles work. They are made mostly from scrap materials.

        You can also choose either 4 inch or 5.5 inch circles. The large ones are easier to read but are more likely to get knocked around in transport.


    2. Rough Cutting the Sides

      The two sides pieces are shown in Figure #3. First cut them as rectangles and then make the 30 degree cut along one side. Bevel this side and the bottom side at 45 degrees making the two pieces a pair.

      Don't cut the curved line yet or the handle holes. You will want to custom shape these.

    3. Mounting the Pipe

      Try taping the two sides together and standing it up. Adjust the width of the legs until the point of the 'V' is at your latitude. When you have this working to suit you, you can mount the pipe axis.

      Install a small block of wood on one side only to support the end of the pipe.

      The large pipe is held to the plywood with four pipe clamps. These must have metal straps across the open end. The pipe mounts right at the edge of the plywood. Drill holes for the clamps and cut away wood on the other side to make room for the clamp. You want there to be a slight crack between the two sides at the 'V' point.

    4. Adjusting the angle

      Install beveled blocks on the sides to mount the shelf.

      Cut a piece of cardboard in the shape of a large triangle with one angle your latitude. Adjust the width of the 'V' until the pipe is at the correct angle.

      Custom cut the ends of the shelf to hold the sides at the right opening. Drill holes for four bolts with wing nuts. You need to remove this shelf to fold the mount for transport.

    5. Lapping the Pipe Joints

      Normal pipe joints do not fit together to make a smooth turning joint. You can lap the two parts together to achieve this goal quite easily.

      The trick is to grind the two pieces of steel to together until they knock the hight spots off each other. This is the normal way you seat valves to rebuild a car engine so the grinding compound is readily available at auto parts stores.

      There joints need to be lapped: the main axis to the 'T', the 'T' to the short nipple, and the short nipple to the flange. Mark the parts with dots made with a punch so that you will not get the parts confused once you have lapped them. Once lapped the pipe must always be assembled the same way.

      Apply a little of the grinding paste to the threads and screw the pipe together until it becomes tight. Then turn the pipe back and forth about an inch. As you proceed the joint should screw farther together. From Time to time take the joint apart, wipe it clean, and apply new joint compound. You should be able to get the joint running very smoothly in about 30 minutes.

      You have successfully completed the lapping when the pipe joint will make one full turn from the point where it is tight back to the point where it feels loose. This test is subjective.

      When you are finished, wash the parts thoroughly with detergent and water in a plastic bucket. Do not wash them in a sink as the can chip the surface (been there, done that). Use an old toothbrush to get down inside the 'T' and deep in the pipe threads.

      Dry the pipe immediately either in hot sunshine or with a hair dryer.

      You will need to lubricate the threads but you do not want to use grease or oil. These collect dirt and can get on your hands and from there to your optics. A small amount of graphite applied with a brush works well. Be sure to wipe off all excess immediately. There is a very good spray dry lubricant that may be available at auto supply stores but it is much more expensive.

      The joints should now run very smoothly. If not you probably did not get all the grit off.

    6. Telescope Tube Mount

      You will have to custom make a mount for your particular telescope tube. The one shown is a piece of wood or plywood with two beveled pieces of molding attached to it.

      The straps shown are large hose clamps cut in half and extended with strips of sheet metal riveted on. Metal straps tend to scratch the tube paint. You can use bungie cords and eye screws if you prefer.

    7. Test Mount the Telescope

      Assemble the pipes, sides, and shelf. Find the center of gravity of the telescope and mount it with is CG in line with the cross pipe.

      The counterweights shown were 'borrowed' from our weight set so I did not include them in the cost estimate. If you do not have any, you can buy them a large sporting good stores. I show them held in place with the clamps from a small one hand barbell.

      Install enough counter weights to balance the telescope. More weight can be put in close or less weight farther out. Too long a pipe gets in the way.

    8. Final Cut the Sides

      Swing the scope around and mark where it hits the sides. Draw a sweeping curve so that the scope mostly misses the sides but enough plywood is left to provide strength. In use you have to step over the legs all the time so you want them fairly low. Make these curves look good.

      Remove the telescope and cut the sides. Also cut hand holes at convenient points along the curve. Round off all sharp corners.

    9. Setting Circles

      There are two setting circles. The ascension circle is in hours and the wheel attaches to the mount with the pointer attached to the telescope support. The declination circle is in degrees and the wheel is attached to the telescope and the pointer to the pipe support.

      In both cases the wheel and the pointer are not hard mounted but can be independently turned by hand to set them. The disk stacks act like clutches. When the telescope moves the pointer moves with respect to the wheel only.

      To use the wheel, you point the telescope to star with known right ascension and declination. Spin the wheels by hand until the numbers are in a good position for viewing. Then spin the pointer to the specific reading for that star. You can then move the telescope while looking at the pointers. When you reach the new right ascension and declination, the target star should be in the telescope field of view (or at least in the finder scope filed of view).

      Cut out the paper setting circles and from sketches #5 and #6. Make two copies of the pointer in Sketch #4 onto clear plastic viewgraph material and cut them out.

      Cut out four 1/8 inch masonite disks the size of the circle. One side must be smooth but the other can be rough. The inner hole should be a loose fit on your pipe and turn easily.

      Cut out two pieces of springy foam like that used for packing electronics the same size as the circles. This foam has to provide springiness to make the clutching work and take up the movement 1/16 inch caused by the turning pipe threads. The thickness of the foam is a bit of a cut-and-try but it should be between 1/4 inch and 1/2 inch.

      Cut out two disks of masonite 1/2 inch smaller in radius than your pointer circle. The inner hole should be a fairly tight fit on the pipe but should still move by hand. Cut two slight smaller similar disks.

      You can either adjust the pipe lengths to suit your setting circles or make the pipes longer and add a wooden locking ring. This is a circle of hardwood with center hole a tight fit on the pipe. You can add two set screw holes to lock the ring on the pipe but drilling a pilot hole. File teeth on the thread end of a scrap bolt to cut the inside treads in the wood.

      Glue the paper disks to one set of disks. You may wish to shellac the paper to make it wear better. Glue the plastic printer to the smaller disk. Assemble the stack of disks as shown in Sketch #4.

      Place the stacks on the pipe frame, and attach the end of the disk stacks to the telescope parts. RTV should work. Fiddle with the pipe adjustments, the foam thickness, and the roughness of the disk surfaces until the circles work proper. You may need to shellac and rough some surfaces or sand others. You may want a small amount of graphite on the inside of the pointer plastic (but not too much).

      By the time you are through fiddling you will understand setting circles.

    10. Folding Up for Transport

      To fold the mount up for transport, mark the location of the telescope mount on its body and of the counterweights with tape. Remove these both.

      Remove the wing nuts from the shelf and set it aside. Loosen the pipe clamp bolts on the one side only and fold the sides together. Be careful not to damage the ascension setting circle.


  5. Finishing

    You may finish your mount any way you like but the plywood should be sealed against ground damp. Telescope bases are usually painted white to make the easier to seen in the dark. We recommend:

    Plywood edges take some effort to seal. The end result should be uniform in texture and not have holes one place and excess filler another.

    First fill all visible holes with glue and wood splinters. Toothpicks work well. Let dry and sand with course paper over a wooden block. Fill with wood putty (I like the powder you mix with water). Let this dry thoroughly and sand again. Seal with a thinned coat of shellac. Sand again and refill. Sand again, seal again, and sand with fine sand paper. In the process you can round the edges of the plywood a little bit. The edges are now ready to be painted.

    Priming the wood with thinned shellac help seal the wood, and helps the paint both to stick and to cover more area.

    Two coats of oil based enamel should last for many years except where you bump your feet.

  6. Completion

    All that is left is to reassemble the mount, relubricate the joints, and install the telescope. Do not get lubricant all over the place.

    Assemble the unit outside and get a feel for the way it moves.


Conclusion

Thanks again for using a Woodware Computer Plan. We very much want to know how you are getting along with your project and would be happy to answer any questions by email.

If you send us a picture of your finished mount, we would be happy to put it on our web page. We need pictures of finished projects with real people standing beside them.


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