Location and first considerations

dome observatory on roof
Aerial view from west of the finished Dome. (Google Earth)
Aerial view from the west of the finished Dome. (Google Earth)

Planning a home-made dome observatory necessitates some degree of planning.

Living in an urban environment in Malta means night-time light pollution can present a problem for the amateur astronomer. Satellite pictures of Malta show it as a resplendent jewel in the darkness of the Mediterranean but unfortunately looking in reverse towards the sky often shows a far from ideal display of the firmament. 

There is also a problem with humidity, that owing to the warm climate and the proximity of the sea tends to be high throughout most of the year and although generally the climate is mild, temperatures can reach 40°C in the summer. Mercifully though in the winter the temperature rarely dips below 8°C and it never freezes.

Wind is capricious and although not sufficient to make harnessing it on a national scale economically viable, we do tend to get  some rather blustery days from time to time especially in autumn and early spring with winds reaching gale force and predominantly north-easterly.

Other factors need to be considered in deciding where to erect the Observatory.  In Malta houses and apartments are almost exclusively constructed using concrete or limestone bricks  and most of the time have their foundations laid directly on bedrock. Roofs are flat and so building an observatory on a roof becomes feasible as vibrations are at a minimum. High ceilings, and insulated roofs also mean that the effect on optics from the rising heat is minimal and only noticeable in the summer months. Finally of course,  the layout has to ensure that the presence of physical structures eclipsing your view is at a minimum. A compromise is almost always necessary.

Aerial view of completed Dome from the South (Google Earth)

Taking all these factors into consideration and having scouted around the roof  in search  for the most suitable location, my son Kevin and I considered the best place to be on the south side overlooking a field. It was decided that the ideal footprint would need to be around 2.2 m square. This would leave enough room to allow for a corridor all the way around the outside and seemed sufficient for an 8 inch reflector. It was decided to make the ‘room’ square and the dome would then rise from a circumferential beam supported by the side walls. A square or a rectangular room has the benefit of providing useful corners for the fitting of equipment and is far easier to deal with than a cylindrical one.

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