Triesnecker was born in Mallon, Kirchberg am Wagram, Austria. When he was 16 he joined the Society of Jesus. He studied philosophy in Vienna and mathematics at Tyrnau, then became a teacher. Following the suppression of the Jesuits in 1773, he moved to Graz to complete his studies in theology, and was ordained soon after his graduation. In 1782 he became assistant director of the Vienna Observatory and 1792 succeeded Maximilian Hell as director. He remained in this post for the rest of his life. In 1794 he was elected Foreign Member of the Göttingen Academy of Sciences and Humanities. During his career he published a number of treatises on astronomy and geography. He was deputy editor of the Ephemerides Astronomicae of Vienna from 1782 until he became editor in 1792. He continued as editor, collaborating with Joanne Bürg, until he retired in 1806. He made a series of measurements of celestial bodies, which were published from 1787 until 1806. These included the Tabulae Mercurii, Martis, Veneris, Solares. He also carried out a long series of determinations of longitude that were noted for their accuracy. The crater Triesnecker on the Moon is named after him.
Works
1787: Dissertatio Lalandi de novo Planeta latine reddita
1789: Tabulae Martis novae ex propriis Elementis constructae. Appendix 2 of Ephemerides Astronomicae Vindobonensem 1789 pp 289-331
1790: Novae Veneris Tabulae ex propriis Elementis constructae. Appendix 2 of Ephemerides Astronomicae Vindobonensem 1790 pp 325-352
1791: Methodus figuram telluris ex Eclipsibus Solis deducendi
1792: Deproprio Motu Stellarum fixarum in Rectascensionem et Declinationem
1793: Tabulae solares novae ex observationibus deductae et ad Meridianum Parisiensem constructae. Appendix 3 of Ephemerides Astronomicae Vindobonensem 1793 pp 401-455
1793: Commentarium De Diminutione Obliquitatis eclipticae saeculari Commentarius. Appendix 4 of Ephemerides Astronomicae Vindobonensem 1793 pp 457-489
1794: Commentarium de De Massa Veneris. Appendix 3 of Ephemerides Astronomicae Vindobonensem 1794 pp 419-435
1795: De usu Aberrationis luminis in tectione Stellarum fixarum per Lunam
1796: Diameter apparens solis, lunae et planetarum cum micrometro objectivo observatus
1798: Catalogus fixarum Caillianus novis observationibus restauratus. Appendix 2 of Ephemerides Astronomicae Vindobonensem 1798 pp 298-310
1799: Longitudines Geographicae variorum locorum e Solis Eclipsibus et fixarum deductae. Appendix 3 of Ephemerides Astronomicae Vindobonensem 1799 pp 328-372
1800: Item Longitudines geographicae
1801: Longitudines geographicae variorum tum Europae tum Americae locorum
1802: Determinationes Longitudinis geographicae diversorum locorum ex Eclipsibus solis et occultationibus fixarum per lunam deductae
1803: Defensio valoris Tabularum suarum lunarium ex plurium pluribus in locis institutis observationibus
1804: Longitudines et latudines fixarum ad annum 1800 cum praecessione. Appendix 2 of Ephemerides Astronomicae Vindobonensem 1804] pp 340-376
1804: De Stella duplici, quae media in cauda ursae majoris. Appendix 3 of Ephemerides Astronomicae Vindobonensem 1804 pp 377-379
1805: Novae Martis Tabulae cum perturbationibus. pp 292-298.
