M42 variable extension ring Kepler

M42 variable extension ring Kepler.

The Kepler M42 extension rings allow you to obtain the necessary travel to achieve a precise focus specific to the various reducers / correctors.

This variable extension ring is composed of 2 elements: a classic extension ring with T-thread and a counter ring. The length of the output T-thread (M42x0.75) is 10 mm long, which is screwed against the ring (1 mm thick). This device allows to obtain a variable extension, from 0 mm (without the counter-ring) to 5 mm (with the counter-ring and leaving a screw-in depth of the female ring of 4 mm, for safety).

If the female ring has a maximum thread depth of 5 mm, the travel can only be varied by 2 to 3 mm, enough to achieve the optimum focus behind an optical corrector or reducer, but in this case it will be necessary to take the remaining thread length into account in the assembly.

Therefore, this ring can serve as an intermediate adjustment ring in a T-thread assembly composed of several extensions; it will allow very fine adjustment of the length to achieve the ideal focus. If possible, the ring should not be placed in the end position to minimize the risk of tilting.

Caution: this ring is not recommended in assemblies involving large photographic sensors, due to the risk of tilt it may cause. In fact, the counter ring does not constitute a support point perfectly perpendicular to the optical axis and may therefore cause a misalignment of the sensor with respect to the optical axis.

• Mechanical inlet type: female T-thread (M42x0.75)
• Mechanical output type: T-thread (M42x0.75) male thread
• Thickness: 0 to 5 mm

Variable extension ring M42 Kepler.