home 16 inch straight 16 inch lowrider
| 16" f/4.5 lowrider |
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This telescope is the Lowrider version of the 16" Design shown here. I built this telescope for our local astronomy club, the Sternfreunde Breisgau. I wanted to build a robust and powerful telescope for our club members and for public viewing sessions using the relatively inexpensive 16 inch mirror sets produced by GSO. The eyepiece height should be low enough to make ladders or steps dispensable even for smaller persons or teenagers. Further, the telescope should be equatorially mounted on an EQ platform, to allow for relaxed observing by the users and their guests.
The concept for this 16" Dobsonian is a similar to that of my 22" Lowrider, except that it is of course smaller and somewhat simplified. Upper cage and mirror box are very similar, while mirror cell, altitude bearings, and rocker box were adapted to the smaller size of the telescope. The telescope is a moderated Lowrider with a zenith eyepiece height of 150 cm (including the EQ platform). The heaviest part is the mirror box with 20 kg (including the 14 kg for the mirror). The telescope can therefore be handled easily by a single person and still gives that feeling of robustness, which is certainly necessary for a telescope used by different observers.
More about planning and making of big Dobs is on these pages.
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The upper cage ...
... is made of 15x15x1 mm aluminum square tubing and lined with thin plywood. The optical axis is bent downward by about 20°, the telescope is hence a moderate Lowrider. The trusses are 20x1 mm aluminum poles connected pair wise by brackets and attached to the upper cage by quick-release fasteners. |
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The telescope has a wire spider of 0.8 mm steel, with crossed wires and an eccentric configuration. The compact secondary holder allows to minimize lever forces. The secondary mirror can be heated with 0.5 W power using a 9V battery block.
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The focuser is a regular Crayford and there are both a red dot and and an 8x50 optical finder. |
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The secondary cage baffles are made from PE sheet material which is painted flat black from one side and attached to the cage using patent fasteners (see here). There are two baffles at the focuser, which allow to minimize the size of the baffles and hence optimize the wind resistance.
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The mirror box ...
... is made of 12 mm plywood with a 9 mm mirror baffle and 9 mm reinforcements in the back. Despite its low profile, it is very sturdy. The altitude bearings are made of 21 mm plywood.
Both mirror and rocker box are etched in mahogany style and coated with several layers of transparent varnish. |
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The lower truss clamps are similar as on Stathis' Cyclopas. The poles have adjustable stops that allow for precise adjustment of the position of the focal plane. The trusses are numbered, such that collimation of the Dobsonian is largely maintained after each set up. |
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The mirror cell is a 6-poin cell made of aluminum, which is sufficient for the 42 mm thick mirror. The cell is attached permanently to the mirror box at one corner (the upper one) and can be collimated using the other two corners. |
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The collimation bolts are accessible from the top, similar as with my 14" telescope. Lateral support is achieved using ball bearings adjustable to the center of gravity line of the mirror. |
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The EQ platform ...
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is a VNS platform and
mostly identical to that of my 22" Dobsonian. Sturdy and with good
tracking
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