1. Lubber-hole decrescendo Areasoner prophase sliping

2. The brightness of the lubber line shall be adjustable but shall not be reducible to zero.

3. After the angular error in the mounting has been corrected and the equipment has been switched on, the difference between lubber line and fore-and-aft-line shall not be greater than 1 °.

4. After the angular error in the mounting has been corrected and the equipment has been switched on, the difference between lubber line and fore-and-aft-line shall not be greater than 1°.

5. After the angular error in the mounting has been corrected and the equipment has been switched on, the difference between lubber line and fore-and-aft-line shall not be greater than 1 degree.