Eric's Astronomy Blog

Design & Construction of Beinn View Observatory

"BeeVOBS"

A 2 metre Octa-Geodesic Dome

An "intuitive engineering" project !

Contents Considerations Design Construction of Plinth & Pier Construction of Base & Floor Construction of Side Frame Construction of Dome Base & Rail Construction of Sides, Door, & Watershed Construction of Geodesic Dome Inside the Dome Windproofing Utilities Costs

Considerations Why bother to build?   Scottish Highlands weather   enough said !  Minimise affects from light pollution   especially security lighting !   Astrophotography   can take 60-90 minutes to set up equipment and accurately polar align   “Organised” observing   all equipment, observing aids, laptop, notebooks, maps at hand   Cheaper than purchasing “off-the-shelf” observatory   £2,000 to £3,000 for ready-made, delivered, and installed What do I want to achieve? Protection from the elements   can observe in light winds   easy shut-down / start-up in e.g. rain showers   minimise / eliminate dewing  Shaded from light pollution   especially security lighting !   Permanent set-up   always accurately polar-aligned   "ready to go" / ready for imaging in <30 minutes   “Organised” observing   all equipment, observing aids, laptop, notebooks, maps at hand   power, internet access   Environmental considerations   maximise renewable / recycled materials   minimise petrochemical derived materials  Security  Minimal cost   £400 - £600 Options & limitations  Shed with roll-off roof   light pollution / dewing?  Rotating dome   spherical / hemispherical vs. geodesic   square base vs. polygonal base   My skills and equipment   no workshop and limited toolkit   never built anything this scale / complexity   Time   after work & weekends ..... but not every spare moment !!!   spring through summer, ready for autumn observing   Appearance   significant input from my wife !  Minimal cost   £400 - £600 Considerations Design Construction of Plinth & Pier Construction of Base & Floor Construction of Side Frame Construction of Dome Base & Rail Construction of Sides, Door, & Watershed Construction of Geodesic Dome Inside the Dome Windproofing Utilities Costs

Design I decided on a wooden plinth because it was readily available, is renewable, and would easily cope with the weight and dynamics of my 8" Meade SCT.  Note that the final height of the plinth is decided by the actual dimensions of  your base floor and preferred observing  height, etc. This turned out to be an ideal and stable  support structure.  Make sure you include all the bracing / joists as indicated to support and distribute your weight across the floor.  I have included the fundamental dimensions and their arithmetic relationships in order to evaluate various size options. Again, this simple frame and bracing structure turned out very firm and stable.  I didn't need the "cantilever" upper braces for the dome rail as the 3"x2"s with 8mm carriage bolts and PVA wood glue was so solid. This excellent website allows you to "play about" with alternative theoretical dome dimensions until you find the one that meets your requirements.  When I was ready for the full-scale construction I was able to accurately mark out and make up my "triangle" templates. Dome modelling my "blue peter" skills put to good use 22 january 2006 I didn't want to commit to building anything as "complex" as a geodesic dome without modelling it first.  As you can see, it turned out just fine and was something with which you could impress friends and neighbours over coffee ! Considerations Design Construction of Plinth & Pier Construction of Base & Floor Construction of Side Frame Construction of Dome Base & Rail Construction of Sides, Door, & Watershed Construction of Geodesic Dome Inside the Dome Windproofing Utilities Costs

Construction of Plinth & Pier Every journey starts with the first step ..................... or shovel ! looking due west 14 may 2006 Little did I know how much work was ahead of me.  I should have got a big clue from this starting point of digging a hole (900 x 900 x 700mm). Journey to the centre of the Earth   2 hours into project ..... 10,000 to go ! 14 may 2006 This first operation took about 3 hours and stuttered due to a couple of boulders and buried batons of wood which had to be levered, sawn, and hacked out. Anyone lost their caber ..... ? 2100 mm 21 may 2006 This bit of timber was originally destined to be sawn and chopped up for firewood.  It has made an excellent and stable plinth for the 8" Meade SCT. Anyone lost their caber ..... ? 15cm nail tie-ins! 21 may 2006 0.6 cubic metres of hand-mixed concrete (sand:aggregate:cement  1:1:1).  A big tip - use a cement mixer!  This took over six hours to complete and was real back-breaking hard work. Anyone lost their caber ..... ? left to cure for four days 21 may 2006 Four days for the concrete base to cure and the entire plinth & pier assembly was permanently in place.  No going back now! Anyone lost their caber ..... ? novel grass cutting 07 june 2006 I couldn't resist cutting a pattern around the plinth & pier to see what the observatory outline might look like. Levelling up threaded rod aligning bolts 07 june 2006 I used threaded rod screwed about 6cm into the timber pier and fixed securely with a nut and washer.  The telescope wedge would be mounted on top of a nut & washer assembly which would facilitate fine levelling adjustment. Levelling up lx50 attached 07 june 2006 A quick "look-see" to check the levelling assembly would work.  The excess length of threaded rod still has to be sawn off. Levelling up mount levelling detail 10 june 2006 This shows the finished levelling assembly. Levelling up plinth complete 10 june 2006 A look at the finished plinth, pier, and levelling assembly with wedge attached. Considerations Design Construction of Plinth & Pier Construction of Base & Floor Construction of Side Frame Construction of Dome Base & Rail Construction of Sides, Door, & Watershed Construction of Geodesic Dome Inside the Dome Windproofing Utilities Costs

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