The text presented here, a letter that accompagnied the gift of an astrolabe, was sent to Pylaemenes, an important military leader whom Synesius had met in Constantinople. It is a brief essay in which Synesius advises politicians to study the sciences (which the author, as always, calls "philosophy"). Synesius also mentions several improvements to the instrument; the model sent to Pylaemenes appears to have been some sort of prototype.
The text is offered in the translation by A. Fitzgerald.
On an Astrolabe 14-18
 Now, having informed myself about you from those who have known you longer than I have, and having known you myself some little time, I am anxious to kindle the sparks of astronomical lore that are lying dormant in your soul, and to raise these aloft by means of your innate qualities. Astronomy itself is a venerable science, and might become a stepping stone to something more august, a science which I think is a convenient passage to mystic theology, for the happy body of heaven has matter underneath it, and its motion has seemed to the leaders in philosophy to be an imitation of mind. It proceeds to its demonstrations in no uncertain way, for it uses as its servants geometry and arithmetic, which it would not be improper to call a fixed standard of truth. I am therefore offering you a gift most befitting for me to give, and for you to receive. It is a work of my own devising, including all that she, my most reverend teacher [Hypatia], helped to contribute, and it was executed by the best hand to be found in our country in the art of the silversmiths.
 Now, concerning this, by explaining it in advance, I should do something useful to the end in view, and the end I have in view is to call out the philosophic impulses in your nature. For if you should acquire an inclination to gaze with straining eyes upon the apparent, then I shall be holding out to you a greater gift, namely, the things which concern knowledge itself. So now turn your mind to what I say concerning what is demonstrated.
 The representation of a spherical surface, maintaining identity of doctrine amidst difference of figures, Hipparchus of old vaguely shadowed, and he was the first to direct his energies to this question. But we, if it is not more than it befits us to say, have finished the weaving of this tissue even to the fringes, and have perfected it. The problem had been neglected in the long intervening time. The great Ptolemy and the divine band of his successors were content to have it as their one useful possession, for the sixteen stars made it sufficient for the night clock. Hipparchus merely transposed these stars and inserted them in the instrument.
 Every allowance must be made for these men, inasmuch as the more important problems were still unsolved, and geometry was still at the nursing stage.note[Apollonius of Perge and Archimedes of Syracuse lived after Hipparchus.] They were therefore obliged to work on hypotheses only. But we, in return for the splendid mass of knowledge that we owe to their achievements, without labor on our own part, should be grateful to these happy men who forestalled us.
 At the same time we esteem it an ambition by no means unworthy of philosophy, to attempt to bring in now certain adornments, to make a work of art and to produce something new of the first order. For even as cities when first founded look only to the necessities of life, to wit how they may be preserved and how they may continue existence, but as they advance are no longer content with what is needful, and rather expend money on the beauty of the porticoes and gymnasia, and the splendor of the forum - so in the case of knowledge, the beginning is engaged with the necessary, only the development with the excellent.