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We propose a simple method for determining the redshift zm at which the angular size of an extragalactic source with fixed proper diameter takes its minimal value. A closed analytical expression, which is often convenient for numerical evaluation is derived. The method is exemplified with the following FRW type expanding universes: the open matter dominated models (ΩΛ = 0), a critical density model with cosmological constant (ΩΛ ≠ 0), and the class of scalar field cosmologies proposed by Ratra and Peebles. The influence of systematic evolutionary effects is briefly discussed. [ABSTRACT FROM AUTHOR]

Details of successful use of a new high speed infrared photometer for recording lunar occultation light curves simultaneously in K (2.2 µm) and L (3.6 µm) bands ate presented. The photometer has also a provision to incorporate a CCD in its light path for quick monitoring and positioning of the optical/IR sources. A motorized flip mirror arrangement for 45° angular movement using stepper motor controlled drive has been put into operation. The change from optical to IR channels can also be triggered by remote control using a radio frequency transmitter-receiver system. Lunar occultation observations of two M3 giants η Gem and µ Gem in K and L bands have been successfully observed. [ABSTRACT FROM AUTHOR]