DOBSONIAN CONSTRUCTION
DOBSONIAN BEARINGS
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| Home DOBSONIAN CONSTRUCTION DOBSONIAN BEARINGS |
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| (1)INTRODUCTION | |||||||||||||||||||||||||||
| (2) CONSTRUCTION | |||||||||||||||||||||||||||
| For general purpose use, it's hard to beat a Dobsonian telescope mount on the basis of rigidity, ease of assembly and use, and last of all - cost. its main drawbacks are - (a) it doesn't track the stars, so frequent fine adjustments are needed, especially when the telescope is used at high magnification, and (b) any jerkiness or stickiness in the movement will make (a) a real chore, and, finally, because of the above, it's not suitable for any astro-photography except very short exposures at small magnification. Nevertheless, the advantages make it seductive, especially the price. | |||||||||||||||||||||||||||
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| INTRODUCTION | |||||||||||||||||||||||||||
| The picture gives the idea. The 'scope tube sits in a cradle held inside a pair of 'wheels' which are supported in trunion bearings on the main stand. This is free to rotate horizontally on a bearing surface. That's all - any more is just lilly-guilding. A with all conventional Dobsonians,this is an alt-azimuth type of mount - so you have to move it in both axes frequently to keep on target. | |||||||||||||||||||||||||||
| Trawling the 'Net turned up plenty of sites and designs for Dobsonians. Putting it all together came down to (a) - the height should be right for comfortable viewing at different 'scope elevations, (b) - rigidity is very important and more height works against that, (c) - the bearing surfaces are the prime problem area, but, they can be changed readily later and (d) - large diameter bearings produce smoother movement. | |||||||||||||||||||||||||||
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| Click for the plans and construction details | |||||||||||||||||||||||||||
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