Thank you rainbowfix and Chris. The Hoyas and cacti ( with the exception of the Euphobia obesa with very small flowers , which is in Melbourne ) are all growing in Selangor. I use a Canon 650 , Canon 450 with extension tube for macro and Lumix LX 5 to shoot the photoes. My wife takes care of the cacti and I look after the Hoyas ( wax fower ) and Bonsai. Cacti flowers only open for a few hours and only 1-2 times a year.
Thank you.

Epiphyllum oxypetallum ( Kheng Fah ) only flower at night and last only for 3 hours. One can literally watch the flower open over a period of 2 hours. Flash has t be used.

Epiphyllum phylanthus, another locally grown Epiphyllum.