Bahtinov-Mask for 80-100mm telescopes

This mask helps to find the sharpest focus possible. To use it place the mask in front of the telescope. The grid in the mask provides strangely looking stellar images which makes the focusing possible. To reach the sharpest focus try to place the middle spike exactly between the two others. To fasten to the telescope use the three small adjustable tabs. The masks are available several different sizes, matching to the given diameters.