So I'm trying to find the focal point of a satellite dish.
I'm not too sure how this dish focuses, as it seems that vertical waves will be focussed differently to horizontal ones, due to the oval shape and that the depths are different depending on which axis is measured.
I ideally want to make a parabolic microphone from this dish. There seems to be a focal point about 60cm from directly above the center of the dish, but when viewed from very off-centre angles, the dish seem to have other points too. How would I determine the "optimal" one?
It is coated in a thin layer of aluminium foil, which I put on to reflect light when finding the focal point.
Unfortunately there are no serial/part numbers, and the dish is missing its feed horn and support so I can't approximate the focal point form there or from datasheet(s).
Any help would be greatly appreciated.
EDIT: Oh and the dish originates in South Africa, and is stamped with a number which looks like a date of manufacture: 19950610. Googling the number yielded no results so its probably a date.