Abstract: An optical device for vertically positioning a sextant to minimize the "tilt error" which occurs in a measured angle of altitude whenever the sextant is not held orthogonal to the horizon. The optical device can be fixed to the sextant and provides in the sextant's viewing area a secondary horizon which will align with the direct horizon only when the sextant is in a vertical orientation. The device is capable of periodic calibration and can be pivoted out of the line of sight when the sextant's user is initially locating the celestial body whose altitude is being measured.

Abstract: A refrigeration system is disclosed which utilizes the rejected heat from the condenser of an air conditioner to heat a second medium such as water for a swimming pool. A control is provided to maintain the temperature of the pool within a given range without degrading the performance of the air conditioning system and actually improving its economy and efficiency of operation. A heat exchanger, to place the second medium in heat exchange relationship with the refrigerant, is placed between the condenser unit and the expansion valve of the refrigeration system. The temperature of the refrigerant entering the heat exchanger is controlled by the on and off cycling of a fan to selectively move air across the coils of the condenser responsive to the temperature of the second medium.