Introduction
Star Focus Filter is used to work with cameras to achieve precise focus on the stars,
Focusing a camera lens in the dark is always a difficult thing in astrophotography. Through the Bahtinov Mask on the filter, Star Focus Filter can help the camera get an accurate focus on stars.
Does it work with zoom lens?
Yes, it's ok for zoom lens. The longer the focus length the better the performance.
Below video is tested with indoor red led,
Canon 600D, Canon EF-S 18-135mm f/3.5-5.6 @18mm