The observatory is in a rural/residential setting on acreage on the north western fringes of Sydney metropolitan area.  The site is located on a north facing slope on the edge of an escarpment in a position where most of the bright Sydney metropolitan sky is obscured by the hill to the south.  There are no neighbours, street lights or other public lighting visible from the observatory.  Lighting from the residence a little distance away can be turned off if required. Typical moonless night average Sky Quality Meter reading is 20.6 magnitude/arcsec2



The observatory was built over several years starting in 1999 with the circular 3.75M diameter concrete slab laid during the construction of the site residence.. The slab is about 200 mm thick with a square opening in the centre providing space for a vibrationally isolated pier.  The 0.5Mx0.5M concrete pier is sunk 0.5M into the sandstone bedrock.  The 30cm thick circular walls were built using recycled sandstone left over from building of landscaping retaining walls.  The heavy walls are not ideal for a small observatory as the temperature probably takes hours to stabilise after sunset but the sandstone does make the observatory look elegant.



The classic hemispherical rotating dome was entirely a DIY design.  The dome base rings were manufactured (rolled) from mild steel angle.  Curved aluminium ribs were rolled from extruded aluminium box sections of various cross sections.  Dome base design


The dome roof is covered by 0.6mm embossed aluminium sheeting.  Expert roofers were required to stretch, glue and rivet roof segments over the ribs.  Dome sliding opening details


Dome Automation


The dome rotation  was recently automated so that the roof opening follows the pointing of the telescope automatically.  The dome is driven by friction using  a rubber tyred aluminium wheel spring loaded against the base ring vertical surface and powered by a geared 40W DC motor.  Mechanical drawing here.  The motor is controlled by custom designed electronics incorporating an Arduino Mega microcontroller and C++ software.  The Dome Controller  communicates with the telescope control software running in the observatory computer via a serial COM port.  The telescope control software continuously transmits the dome target position to the Dome Controller  which attempts to drive the dome to the required position by optically reading and counting 1 degree spaced marks on the dome base ring.  In manual mode the dome can be driven in either direction by two pushbuttons.




The C14 fork mount is bolted to a pier made from 300mm 0.5in thick steel pipe segments with the mounting surface machined and angled to the local latitude. Pier design




Geographical co-ordinates

Longitude           151.0711E

Latitude               -33.6211


IAU Site code             E23


ASA  Designation      DO3-48


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 To contact us:      | E-mail: andras@arcadiaobservatory.org