We highly advise against visual calcium observations of the sun - the 397nm of Calcium are already ultraviolet radiation, and UV-radiation can cause phototoxic reactions which can harm your eyes. In addition, even young people can't see these wavelengths very good, and sensitivity decreases with the age. Because of this, the eye doesn't feel if the intensity is much too high. If you now try to increase the amount of radiation (e.g. with another mirror) to achieve a brighter image, you will increase the risk for eye damage. According to the newest norms for eye safety and to ophtalmologist conclusions, the sun must not be observed visualy at 397nm.
We highly advise to only observe the sun in calcium photographically, then you also do not need a star diagonal. We can't understand why some manufacturers promote these calcium-filters for visual observations.
We also advise against placing a filter so close to the focus - any energy rejection filter belongs in front of the front lens, even if this sets high demands to the quality of such a large filter. Placing the filter close to the focus will save money, because you can use a much smaller filter, be we absolutely can't recommend it - because of our own conscience as well as because of EU-regulations. The filter would receive all the energy collected by the front lens. We can only recommend putting the energy rejection in front of the front lens, which is the ethically and technically correct method.
The M68-star-diagonal hasn't got this simple option for reconfiguration to 2"-SC-thread. But you can use
- Baader M68 Conversion Ring # 2458195 to change the male M68-thread of the star diagonal to a female thread (https://www.baader-planetarium.com/en/baader-m68-conversion-ring.html)
- M68 to 2" UNFi Conversion Ring # 2458232 to change the female M68 to female SC-thread (https://www.baader-planetarium.com/en/m68-to-2%22-unfi-conversion-ring.html)
- Baader 2" NexStar locking ring. # 2458270 as a counter nut to set the orientation of the star diagonal at the telescope (otherwise it would stop wherever the thread ends). https://www.baader-planetarium.com/en/baader-2%22-nexstar-locking-ring..html
Of, course, this isn't a cheap solution as one more adapter is required, but I'd recommend the NexStar Locking ring whenever you want to screw a star diagonal onto a Schmidt-Cassegrain.
Baader 2" ClickLock® Diagonal Mirror M36 thread (Zeiss)
- Telescope side with Carl Zeiss M68 thread / optical length = 109 mm
- Scratch resistant hard coated mirror surface for safe cleaning, to remain scratch free even if subjected to harsh environment
- Mirror rejects deep UV and IR radiation, safe for solar viewing with all White-Light and H-alpha solar filters
- Baader 2" ClickLock clamp for ultrafast clamping action
- Clamps heavy accessories effortless, with fingertip action
- DC design as # 2956100: Instead of 2" Safety Kerf nosepiece it has a M68 thread, which makes it possible to mount the mirrors on our extensive range M68 with the largest possible passage on many telescopes
|Optical Design||Mirror Diagonal|
|Inner Connection (lens sided)||Thread, M48|
|Outer Connection (lens sided)||Thread, M68 x 1|
|Inner Connection (eyepiece/-camera-sided)||Clamp, 2" (50,8mm)|
|Reflection surface||Dielectrically coated|
|Image Orientation||Erect image, Mirror inverted|
|Optical length (mm)||109|
|Inner Diameter / Clear Aperture (mm)||46,6|