It would be worthwhile › Forums › Telescopes › Mystery lens and optics tube? › It would be worthwhile 20 January 2022 at 12:58 am #585138 Denis BuczynskiParticipant It would be worthwhile measuring the focal length , the original Mond Zeiss 7 inch was f/7. Also have a look at the 7 inch Zeiss triplet lens that we sent back to NLO (the one Harold Ridley passed on to Glyn) and see if they are similar.
