Yet over the next few years Herschel’s interest in double stars again increased. One factor in this appears to be Struve’s publications. In an 1828 letter to his friend and fellow astronomer Francis Baily (1774–1844), Herschel wrote that ‘the more I see of the Catalogue [of Struve’s double star observations] the more I am disposed to value it.’ He admitted that his own refracting telescope (which he did end up purchasing from South) could not resolve many of the star pairs in Struve’s catalog and that Struve’s refractor at his observatory in Dorpat ‘must indeed be a jewel without price.’ This realization, however, far from demoralizing Herschel, energized him to improve the capability of the 20-foot reflecting telescope originally constructed by his father. ‘I mean to try my hand at a new mirror. . .’ he wrote to Baily. ‘I shall work at it till it is decidedly superior to my present, then put that on the tool again, and so on alter- nately, till I get something really good.’17 The project of improving his own instruments was successful, for in 1829 Herschel published a catalog made with the 20-foot reflector containing almost 300 double stars of his own discovery.18 Besides improving the mirrors of this instrument, he also augmented its capabilities by installing a micrometer, which, he wrote, would allow him to ‘give measures, not estimates’ of all his double stars.19 The new arrangement worked so well for double star observations that he almost regretted the time and labor he had ‘wasted on inferior instruments,’ though, he main-tained, despite this lost time ‘it is not yet too late.’20 This same year, apparently making up for lost time, Herschel published what he referred to as his third series of double star observations, containing almost 400 newly- discovered double stars. A fourth series followed in 1831.21 Despite his comments on the superiority of the 20-foot reflector, he supplemented his work on it with two catalogs published in 1833 and 1835 of micrometrical measurements of double stars using his 7-foot refractor.22 His fifth catalog of double stars was published in 1833, followed by a sixth in 1836 and a seventh near the end of his life in 1871, all of which were based on observations made with the 20-foot reflector.23 In 1858, responding to a question about the total number of known double stars, he noted that his own catalogs included 5449 such bodies of his own discovery.24 At the time of his death, he was compiling a catalog of double star observations that totaled over ten thousand.25 From the extent of his work on double stars, it is evident that despite his comments on their secondary nature in his observations, the discovery and cataloging of these objects was a major part of Herschel’s astronomical career throughout his life. Along with Struve, he was recognized as an authority in the field that he and his father had largely created. Yet what motivated this enduring inter-est? An examination of Herschel’s correspondence shows the large role that the task of distinguishing between optical doubles and binaries as well as verifying his father’s theories played in his work. What are absent, however, are any clear antecedents to his speculations on the planetary nature of double star companions published in his 1833 work. Views ‘tres Philosophiques en tres vraise’ William Herschel began his observations of double stars with the intention of measuring parallax. Though John Herschel was also interested in this problem as he began revisiting his father’s double stars, his correspondence from this period indicates he was more interested in con-firming what his father had accidentally discovered while searching for parallax: binary stars. This motivation is expressed most clearly in correspondence with his aunt and William’s long-time scientific partner, Caroline Herschel (1750–1848). In a letter from August 1823, during the period Herschel and South were completing observa-tions for their first catalog, Herschel wrote that to his satisfaction his work with South had produced results which ‘in most instances confirm and establish my father’s views in a remarkable manner.’ Caroline was fiercely loyal to her brother’s work, and much of Herschel’s dialog with her regarding double stars was couched in terms of filial duty. He told her, for instance, that he thought he ‘shall be adding more to his [William’s] fame by pursuing and verifying his observations’ then by simply republishing them.26 Two years later, by which time Herschel and South’s first catalog had been published, he wrote to her that he would soon be sending the paper that confirmed his father’s theories. Among the 380 double stars in this catalog, he wrote, ‘we have now verified not less than seventeen connected in binary systems in the way pointed out by my father, and twenty-eight at least in which no doubt of a material change having taken place can exist.’27