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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

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  1. B

    Star Test Result Question

    99mm aperture and more so 115mm aperture spotting scopes need longer focal ratios for broadly similar performance. So perhaps f/7 to f/7.5 and f/8.5. In addition if the Kowa 99mm is more compact it suggests a stronger telephoto component. Also fluorite crystal is not easy to work with and to...
  2. B

    Star Test Result Question

    Is the difference because of prism type and the speed of the system? Regards, B.