Using a star filter is simple, just install it in front of the camera lens. 

Star filter is a special effect filter which adds stars from highlights in the camera frame to your images and videos. No need to change aperture. Made of best quality optical glass. 

You can of course choose shorter exposure times because of the open aperture, which may be an advantage in the shade, in the evening or in dark corners, especially if you are taking photos without a tripod. Where desired, the bokeh is also a dream. The depth of field can really play off best in strong foreground-background contrasts, such as in portraits. It's possible that the crop factor, e.g. with small format cameras like my 550 D, ensures that you get a slight telephoto effect, i.e. you might not get a complete sky on it at all. 

I had to wait for a clear night. I tried all of my binoculars. NONE were suitable for star gazing. They magnified the dark sky. On a tripod you can see a speck of light. 

1. You could consult us or search the mount information online
2. You could find the mount information on your instruction book when purchase the lens/camera
3. The mount information may be showed on front of the lens, side of the lens, rear of the lens or on the lens cap, usually it is a 2 or 3 letter code such as: CN, FD, OM, MAF, NK, N/AIS or F/AX