Building a Dobson Telescope

The most fun thing I did in the summer of 2014, was building my own Dobson telescope. More than 35 years ago I build a Newton telescope, with a paralactic mount. This telescope was catching dust because of the better scopes I bought. What a waiste. So, in spring 2014 I decided to give this scope a second live and turn it into a Dobson grab-and-go scope. With the optics being in good shape, the “only thing I had to do was to build my own mount. Being stubborn it wasn’t good enough to grab a drawing from the internet and build on. No! I had to design one for myself. So, of to the drawing board I went. With a sketch of “the general idea” I went to the local DIY store to get some materials.

10012554_1492875050936154_137787861_nFirst step was to build the rockerbox. Out of multiplex board I made a square box: The scope had to fit in and the bearing wheels had to fit onto the outside. This had to fit very precise. After sawing and some grinding it had the desired measurments and a could get tot step two: the bearings for vertical movement. I had choosen for PVC bearings.1978616_1492875814269411_72279875_n They are light in weight and the surfaces slide well. So, on each side of the telescope box, a PVC end cap was fitted. The placement of both caps was also very precise. The caps were fitted by placing them over a wooden groundplate. They were cut in the same diameter as the inside diameter of the caps. By skrewing the groundplates to the box, and gleuing the cape on top of them, they needed no extra mounting materials. The groundplates also provided extra support at the inside of the cap. Also the bearings were cut out of wood. 10155310_1492876390936020_1547384846_nBy sawing and grinding a cruve was made slightly greater than the PVC caps. They had to be slightly bigger to fit in the PVC layer to let both parts slide in an effortless and smooth way. This took a lot of grinding: both parts had to fit precise! The PVC surface was cut from a piece of pipe and glued into place with super glue. In this way two of those barings were made. While the glue had to dry, work was started on the mount itself.

1560662_1492876944269298_308219604_nOn the picture on the right you’ll see the basic form of the mount. The measurements of thids mount has to be precise too. The bearings have to be fitted and the rockerbox and the PVC caps have to fit in snuggly. The mount is also made out of 22 mm multiplex.

1560446_1492877780935881_338997887_nNext step was fitting the bearings. In the picture below you’ll see the bearings mounted into place. The place of the bearings had to be precise too. On one side the hight of the bearing at the mount was determined by measuring the right height. The otherside was mounted at precise waterlevel hight. This way, the telescope was level and the hight of both bearings right. After letting the glue dry for a day an exciting moment came: would the rockerbox fit into the mount and would it rotate as planned? 923560_1492878070935852_75295694_nWell, as you can see, it did fit perfectly. The main job on the Dobson was done! Like I said at the beginning of this page, this had to be a Grab-and-go telescope. By its size the mount would be easy to handle. Its weight was light and it had enough point to “grab”. The telescope itself is larger, heavier en more delicate to handle. From my kitchen project I still had a door handle laying around. This handle fitted perfectly on the rockerbox. This way the telescope was also easy (and save) to handle.

10154147_1492878550935804_1181582745_nLast phase was fitting a groundplate. The plate itself was made out of a 30 mm wooden plate. I used two lexan plates and some grease to let the two surfaces glyde effordlessly. This way the telescope could make a smooth horizontal movement. The bearings provided a vertical movement. 1970862_1492943667595959_1497037620_nAfter just one week the telescope neared completion. Just one more job to do: choose colours en paint the thing. Black for the mount was an easy choice. The telescope itself was a little tricky. The pipe was painted in silver but had some signs of wear and tear. The new colour had to be sparkling, fresh and new. It also had to be strong so  little scratches would be visible easily. So I chose bright blue carpaint. Easy to paint and very hard once dry. All these steps resulted in the telescope below. Lightweight, easy to transport and a great way to observe the heavens.

10155751_1498032233753769_8443570863022868020_nIt just needed a final detail: a finderscope. I remebered I had a red-dot-finder somewhere in a drawer. After looking for it for over an hour I finaly found it. 10271643_1499517323605260_1060002195266363267_nBatterys dead but still intact. I made a little “shoe” out of aluminum and fitted that onto the telescope. This way the red-dot-finder could be easely mounted and removed again. The only thing left to do? Wait for clear skies and a chance to aline the the optics and see what this scope is capible of :-).

 

 

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