One of the critical points for good quality astrophotography is focusing. There are many aids to this, one of the best being the Bahtinov mask, which has rectangular holes cut at different angles to each other. Put it on the front of the telescope and forget that focusing is a complicated operation!
When using a Bahtinov mask, 3 pairs of diffraction spikes appear around the stars, the middle of which moves during focusing. When this is observed exactly between the other diffraction spikes, sharpness is ideal.
This professionally made Bahtinov mask promises durable and precise use. Thanks to the oval hole in the mask's "ears", it is easy to adjust the mask to the correct tube within certain limits. Thanks to the screw solution, the mask is easy to dismantle and reassemble, and its size can be easily adjusted. Thanks to the cylindrical design of the prongs, the masks are easier to place on the tube than models with hexagonal prongs.
When making your choice, be sure to select a model that matches the outer (or inner) size of your dewcap. The nominal size of the mask is the recommended telescope diameter.