Ryehill Observatory

Design thoughts

The biggest observatory design decision most people have to make is whether to go for a roll off roof or a dome. The siting of the observatory above an existing shed took that choice away from me, a dome was the only practical option. Roll of designs have the advantage of usually being cheaper, easier to construct, can blend into a garden setting better, give a full view of the sky and aren't prone to the same "seeing" problems associated with the small apertures of domes. On the other hand, domes provide more shelter from the wind and shading from bright light sources, dew is much less of a problem and observing in the dome is a warmer more comfortable experience.

My greatest concerns were around the seeing problems especially since the observatory has a lot of heat retaining brick and concrete beneath and around it. I have installed 2 good sized extractor fans to encourage a steady flow of air into the dome through the aperture rather than having warm air pockets convecting out. Once the scope has been aligned the whole imaging operation can be controlled remotely. This gets rid of one major heat source - me!

To encourage the air in the dome to reach outside temperature a number of air bricks have been built into the walls. These can be blocked up when the dome is in use and the extractor fans are working.

I have been concerned about damp conditions (this is the UK remember!) affecting the equipment. Sealing off the dome and using a dehumidifier is impractical and also works against equalizing the temperature with the outside. To reduce potential problems the scopes, mount and cameras are protected by a large, waterproof but breathable motor bike cover. Under this is a small lamp equipped with a low energy 7W bulb. This should hopefully raise the temp around the equipment to a couple of degrees above ambient.

The dome is a 2.7m pulsar complete with drive. I haven't gone to the expense of a PC controllable dome since I'm not planning on operating the observatory when away from home.

Construction Pictures

This was the brick garden shed sitting in a rather neglected work-a-day corner of the garden before construction.
The walls were built up and the ceiling of the shed lowered.

The shed ceiling has been lowered and the brick walls are being built up to their final height

The shed ceiling has been lowered and the brick walls are being built up to their final height.
This picture shows the view to the south east

The dome sits on this raised plinth to keep it well above any pooling water

Construction of the 2.7m Pulsar dome was straightforward

Paul and Alex at work on a fine June day.

The floor of the existing building had several layers of concrete, some reinforced, 20 inch depth.
A 1m square and deep hole was opened up through this and the concrete plug keyed into the existing floor.

The entrance is through a doorway through what was the back wall of the adjoining garage. Here it is under construction

Nearing completion here. The large tree to the right largely obstructs the view to the north
although, surprisingly, I can still see polaris through the polar alignment scope.

This picture shows the installed Epsilon pier with Tak EM200 mount, 250mm LX200ACF, QSI 532 and SX AO unit. Lots of wires which I've managed to tidy up a little! You can also see the drive unit for the dome.

This picture shows the 20x20inch concrete tower coming up from the floor below. It rises about 6" above the floor of the observatory as a result of the rather high up stand supplied with the Pulsar dome. In the background you and also see my FSQ 106, part of a GSO 8" F4 newt, one of the extractor fans and a collection of dew straps.

In Operation

So far Ryehill Observatory has worked out as hoped. The seeing has been excellent on occasions which has been a relief.; The extra height has made a huge difference to the view compared with being down in the garden. It is such a pleasure to be able to walk in, switch on and be up and running. Just a shame it do anything with the weather