The treatise's author adds that the best observational instrument to date was the "azimuth instrument" (alat-i samtiyya) invented by Abu 1-'Abba's al-Lawkari, which, however, also suffered from the above-mentioned issues.
However, azimuth instruments (in the sense of the instruments specifically used in the simultaneous measurements of altitude and azimuth) were apparently not so novel.
Therefore, we can consider at most five observational instruments (apparently models of azimuth instruments) to have been innovative in the Islamic period up to Ghazan Khan's time, over a period of five centuries.
