
Brian
Therefore I anticipate the internal etalon will require vacuum tuning, or need retuning of the CWL to allow for pressure tuning.The evolution of internal etalons has taken several steps. The original systems had internal fixed etalons that sat behind a re-collimating lens set (these lenses work to bring the light rays back to parallel). The light from the etalon was then re-focused back to the image plane. These systems cannot compensate for changes in altitude and air pressure. Taking this system from sea level to 8,000ft would not work...
The next step is the introduction of some tilt. This works similar to the tilt on the front of a system. However, due to both off axis light rays that could not be re-collimated with a simple lens, and the angles created by the Sun’s size, the etalon can only be tilted thru a fraction of a front mounted system... The removal of the tilting from the internal system is providing stunning results... This [Doppler True (pressure) tuning] technology has certainly improved the dedicated system...(Empahsis added)
Hi DerekThanks Bob does that mean you need a bit more tilt or that's it as far as being on band?
Why not ask Mr. John Hunter to determinate the necessary spacers thickness, to make them and to assemble the etaion at the LM laboratory?
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Typically we charge about US$20,000 for large aperture etalons, I expect the repair would be about half of that (and may not be successful).
Thanks Alexandra -- me too! And if not, I have vowed to give up solar astronomy and take up stamp collecting ;-)Oh dear Bob, I hope they fix it soon and the dream will come true
Hi Achim,the two etalons must be rotated against each other to find the best h-alpha...or a Fraunhofer-refraktor, which is corrected at the red wavelenght... Sorry, the SM140 is not the "Holy-Grail", because there are worldwide 4 pieces of a Lunt 160 frontetalon....
Hoping to have additional updates in the coming weeks. Again -- much appreciation to Andy for his efforts... Two thumbs up!Hi Bob,
Yes we have.. : )
The front mounted etalon was completely reworked. We took the etalon apart and re-assembled using new spacers. The bad news is it took 10 attempts, the good news is that we were able to get the etalon to a uniform and excellent tune. Only a very slight tilt will be required.
The internal etalon is very close to be ideal being just slightly high.
To compensate for this we are going to re-house the etalon and change it's tuning point slight lower.
I imagine that this will be completed by end of next week.
I did test the IR ERF and found the surface to be very good.
Let me know if you have any questions.
Best Regards,
Andy Lunt