Javascript and/ or Php project

Hi I am looking for somebody to write a field of view calculator for a website. I can do the maths but the Java is not my thing.

I need a be page that does this...

So I have a list of Telescope makers their telescopes and the scopes aperture size and focal length.
I also have a list of Camera makers, their cameras and the cameras x and y chip size and pixel size.
I want a user to select a telescope maker from a dropdown and that to populate a drop down of telescope make by that maker on selecting that the aperture size and focal length is determined
The same happens with cameras but we get the pixel the pixel scale and chip x & y size.
There is a third dropdown that selects a focal length reducer or multiplier. This just changes the telescopes effective focal length.
A forth drop down selects an image.
The calculated field of view and pixel scale is displayed (I can provide the maths)
The selected image is rescale to the right pixel scale and a rectangle is overlaid showing the calculated field of view. This image is displayed.

Note they are a number of sites doing something similar.

I expect that their might be some future development work once the site is running. This will be extra.