Its a shed Jim - but not as we know it...

The Observatory is located in Stoney Hills, near Burnham-on-Crouch, Essex, in the South East of England. Despite the name, Stoney Hills is only at an altitude of 14 meters above sea level, but it is above the surrounding fields. It is also about a mile from most street lights so local light pollution is fairly low (relative to the rest of Southern England anyway)

The observatory is a ‘roll off roof’ design. To construct the observatory I used a standard good quality shed, 10’ x 10’ (3m x 3m) square. An interior wooden frame was made to add strength and to support the rails that allow the roof to roll. The roof itself has 2 extra ‘A’ frames supporting it with vertical and lateral castors to the side rails. The roof rolls off leaving the front of the shed in place but taking the top of the rear wall with it. The roof’s ‘A’ frames are designed with the maximum clearance under them possible. This allows the scope to be mounted high up near the roof apex, giving a less obstructed view when in operation.

The building is aligned east / west so that the lowest unobstructed view for the scope is north / south. The reasoning behind this is that any astronomical objects low in the east or west and hidden by the structure will appear higher in the sky and be visible ether later that night or at a different time of year. Objects low to the southern horizon will always be low in the south and would otherwise never be observable.

The telescope itself is mounted on a custom pier fabricated from 2.5 mm and 10 mm marine grade stainless steel. The main tube was rolled from sheet to 320 mm diameter and the top and bottom flanges are laser cut plate. The construction is fully precision TIG welded and then powder coated. There are numerous trays and power outlets fitted to the outside. These are removable should they cause the electrical cables to snag, but so far this hasn’t been a problem. Leveling is provided by a removable top plate assembly which is mounted on a ring of adjustable bolts. This also allows for easy modification to enable different equipment to be used in the future. The pier tube is currently hollow but was designed to be filled with sand to damp out any vibrations. This has not been required as the pier’s high lateral and torsional stiffness gives it a main resonate frequency of about 600 hz. Under damped oscillations below this are lower than the limits I can measure. The transmissibility of low frequency vibration caused by wind or the telescope itself is therefore negligible and far exceeds the characteristics of the LX200GPS fork mount Please see CAD Images for more details.

The pier passes through the building’s floor without touching and is bolted directly to the concrete base. The base consists of 2 tons of hardcore and about 8 tons of structural concrete. The pier was ‘floated’ on a slurry of fine cement before bolting down to ensure a good mechanical coupling between it and the base.

The base does not have any vibration isolation between it and the surrounding ground since the main sources of vibration in the area are only the people in the observatory and the equipment itself. Ground isolation would have reduced stiffness and potentially caused a lower resonate frequency in the pier assembly. However, the wooden floor of the shed has a layer of foam and a second floor mounted on that to dampen the effects of people walking around. This also helps to lessen thermal effects from the warmer concrete at night. A floor with a little ‘give’ also pays for itself if you drop an expensive eyepiece...

With the roof on there is a 2 stage heating system to ensure the internal temperature stays above 5 degrees Centigrade or so to avoid frost and condensation problems. Heating strips on the scopes front cell’s also cut in automatically at low temperatures. The air is automatically filtered and dehumidified - very useful when the roofs been open all night and the inside is damp.

Power is supplied by 100 meters of armored underground cabling along with twin Cat 5e network links, CCTV, phone and alarm. Robotic control of the scope and systems is available via, the local network or Internet.

All in all I’ve tried to consider everything I can in the construction of the shed and get as many things working with me rather than against me as possible, in fact I’ve probably over done some aspects of it (My wife thinks so...) but I’ve enjoyed myself doing it and at the end of the day that’s what makes it all worthwhile!

Please click on the images below;