AS2 Communicator
AS2 Communicator is able to connect to other ASCOM compatible applications and synchronize the dome to the telescope and other scientific equipment. It uses its internal 3D software models of both dome and telescope mount for predicting the target azimuth of the dome with respect to the actual telescope pointing. If accurate geometrical data is provided by operators, dome motion can be controlled to a high degree of precision.
AS2 Communicator also exposes a set of bublic variables which can be accesses by any other ASCOM compatible application, which enables easy upgrading of existing AS2 Communicator abbilities. For example, custom software routines for advanced air conditioning control are easy to implement by observatory operators.
Note on dome motion control method
When considering the type of dome motion control, a question whether continual or intermittent dome motion better suites telescope needs sometimes arises. The answer is practically unanimously - intermittent, and there are several good reasons for this:
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Mathematical equations used for calculating ideal dome azimuth are highly non-linear with respect to constant telescope tracking of celestial objects. For any telescope mount type, there are areas for which dome needs to be practically stationary, while for some other areas dome has to move rather fast. The fastest dome motion is often necessary when the telescope tracks a celestial object passing near the zenith - dome door then has to switch rapidly from looking east to looking west. It may seem strange at first, but the ratio between the two extremal angular speeds easily exceeds 1:1000.
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Practically no electric motor powerful enough to move the dome can be controlled in such a huge speed ratio just mentioned above. The realistic figure is closer to 1:20, with motor torque falling rapidly out of this range. The solution to this technical problem could be introduction of variable gearing ratio mechanical transmission, but in this particular case that would unnecessarily complicate the system leading to significant loss of durability and reliability.
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Even if dome motors could be controlled in continuous fashion, power dissipation that constantly powered-on motors would inevitably produce would easily lead to observable spoiling of astronomical seeing. Motors are the most efficient (in terms of energy) when left operating at their designed (natural) maximum speed. The more external control is applied to them, the higher percentage of electrical energy fed to motors eventually becomes converted to heat. Because of the inevitable energy losses as high as 15%, variable ratio gear boxes would make this problem even worse...
Taking everything into account it becomes clear why astronomical observatory operators prefer to control telescope motion continuously and very precisely, which is obviously necessary for achieving long exposures, while at the same time they try to move domes as rarely as possible.
