General Requirement for the Design of the LLMC

In general the design of the LLMC should make its observation suitable for its new observational principle and for the eliminations of the deformations from both gravity and heating.The instrument should be able to observe a star alternatively in the meridian and the prime vertial directions so that the azimuth error and the instant latitude can be absolutely determined.In practice, it can be rotated around its horizontal axis like a transit instrument during observation, therefore, the absolute determinations for some errors can change into the relative determination.It needs an autocollimative plane mirror in the tube.The plane mirror together with the primary and secondary mirrors form an autocollimative system to measure in real time the change of the optical axis.The change contains the flexure of the tube, the displace and rotation between the primary and secondary mirrors. An axis collimationer is required to measure the irregularity of the privots and the heat deformations between two privots.At last, a new method is needed to measure the level error in place of a traditional vial.