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I keep looking at different, dome shutter arrangements. A choice must be made for the new dome. The following monologue is a very personal viewpoint and beauty is strictly in the eye of the beholder.
Bi-parting shutters are quick to operate and quiet in movement. They [usually] need no springs, ropes, chains nor counterweights to operate. They provide the full width of the observation slit or only a fraction of it when windy. They can reach well over the zenith depending on the designer's wishes. Bi-parting shutters are more traditional. Even non-astronomers would instantly recognise they belonged to an observatory.
There is no large tray at the dome's "chin" to catch the rain or the wind. The supporting slides can be heavy duty draw slides in amateur scale domes. The use of pipes with linear bearings is another option. Linear bearings can be normal ball races. Arranged, radially around a pipe. The slides, pipes and bearings can be hidden inside the [closed] shutters for weather protection.
Bi-parting shutters can be high or low profile on the dome. They must clear the dome when opening and closing. High profile shutters will tend to catch the wind. Potentially causing unwanted shutter movement, when open. Unless latches or door bolts are employed.
I use door bolts after the shutters closed once too often in a breeze. These lock the shutters in both open and closed positions. Ropes can be arranged, with eyes or pulleys, to close the shutters at the top. Useful when the observer is barely able to reach the bottom of the shutters. Where there are tall observatory walls. More typical of refractor observatories. My own base ing is at eye level. Requiring a step-up to be able to see the ground and/or persons standing outside.
I can usually rely on momentum of the whole shutter to close from top to bottom as one. Oddly, I completely overlooked the wind direction when gluing the weather overlap to the eastern shutter. With the dome usually parked facing south the prevailing south-westerlies can drive rain under this weather strip.
It would be possible to provide spherical shutters which cling closer to the dome. Though this would would require a concave mould be made to produce the convex, spherical surfaces. A great deal of work required just to lower the wind resistance.
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Then there is the large "chin" tray which blocks the view to the horizon when closed. Why do they never hinge these trays to allow them to hang vertically downwards? That would stop them collecting rain and their wind catching profile would be greatly improved. All at the cost of making it rather more difficult to lift them back up again from inside the dome. I find them very unattractive when open.
The "chin" tray can be left in the closed position to provide wind protection inside the dome above certain pointing altitudes.. Without the chin tray the shutter is too long to clear the zenith. The shutter must stop safely before it damages the rear of the dome and/or the shutter itself.
There are more complex alternatives to bi-parting. Or up-and-over shutters. A Danish, amateur astronomer's dome has a series of overlapping, hinged doors. Not having discussed the arrangement with the owner I have no idea if it is successful. Or suffers from unforeseen drawbacks.
The overlaps are obviously intended to shed rain when closed. Being serial, in nature, they must [surely] all need to be opened in a set sequence. Once they are all opened certain doors can then be closed individually to block the wind or stray light. As I study this image I see a cover at the top and extending down the rear of the dome. Suggesting that it is an up-and-over shutter but with serious complications.
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