Abstract
DURING the past summer, in the Transactions of the Optical Society, Mr. J. W. Gifford has directed attention anew to the question as to the two wave-lengths most suitable for achromatising telescope objectives. Mr. Gifford has constructed telescopes in which the paraxial focal length for the D and E lines is the same, and, judging by the performance of such objectives, he considers such a choice superior to the more customary choice of the C and F lines. By a different path I have been led to a similar judgment, at least for telescopes of large aperture.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
