The ideal situation is to have the focuser behind the etalon so the etalon can remain fixed at the desired 200mm . My local scope shop had a used Moonlight without an adapter for a good price so I purchased it and made the adapter I needed for this purpose . The pic below is the re configured mod utilizing the Moonlight .
I had one more issue I needed to deal with and that was the focuser that I was using in the scope . I had adapted a "low profile" focuser designed for a Newt , I used this short focuser to avoid having to cut the tube . The issue it had was the short body focuser did not offer enough support to prevent the optical train from sagging . The solution was to shorten the tube by 3" and go back to the original focuser as it offered better support and can be locked squarely . It's purpose now will be to position and lock the etalon , all focusing will be done with the moonlight .
The images below are from the first test run with this new combination .
6 comments:
Great write up Mike! Now for some testing weather.
Great mod Mike! You and Bill are always on the edge and your fantastic images show it!
Thank you Chris , one thing you can count on is that Bill and I will never stop thinking , especially when it is cloudy . Too bad we can not discuss these scopes on the forum .
I see that you eventually cut the scope back by three inches, Mike.
Was three inches necessary? I seem to recall two inches as the magic number. Oh..we are talking about the 102 here..aren't we??
Hello Bob , The main issue we wanted to eliminate was the fact that with the original configuration we were moving the etalon every time we focused . The best case is to have the etalon fixed at the 200mm into the optical path and have the focuser behind it .Our initial tests have shown much better etalon (sweet spot) control with the etalon left at or close to the 200mm . I was able to avoid cutting my tube (102 XLT)by adapting a Low profile Antares focuser to this scope . this presented a bigger issue in that the short focuser did not offer enough support to keep the mod aligned without drooping out of square . So last week I removed the Antares focuser , cut 3" off the tube and returned the original focuser to the scope . I now use the original focuser to position and lock the etalon and do all focusing with the Moonlight . The scope now puts the etalon at the 200mm spot with the original focuser extended 1" , this has left me 1" of inward travel to see if there is any advantage in placing the etalon further up stream . More testing is required but initial tests have shown much better results .
I also am considering the fixed etalon position and am leaning in that direction. Cutting off a few inches or three of the tube is not an issue as it was purchased specifically for this mod.
Thanks for posting your efforts and results as it lets people like me benefit from your work without the necessary trial and error that I know is involved
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