Thanks @Peter.

I already have the L-eXtreme and the Baader OIII filters. I agree that the OIII filter is not designed for the DSLR camera. But I experimented with separating the Red (in the grayscale) as Ha and the G+B (both in the grayscale) as OIII and I have to say that the results look very positive. I know what the RGGB mask is and I'm very optimistic in the idea that the double G and B can collect some significant amount of proper photons. My Canon 6D is modded, so it collects too much red light, so the separation is difficult. But I am considering adding a stack of the extra OIII subs to the G+B channels. Just look at my pics of the Heart and the Soul nebulas post processed in the typical way and in the new approach:

www.astrobin.com/users/Vroobel/

Finally I know why the pre-focusing as best as possible before the run of the focusing is so crucial. I'm going to find the best initial position using a Bahtinov mask that I designed and printed (satakagi.github.io/tribahtinovWebApps/Bahtinov.html). Since then my routine will be as follow:

1. Zeroing the position with forcing the real zero at the EAF as well,
2. Moving to the position defined experimentally with the Bahtinov mask,
3. Running the focusing procedure.

I found that after positioning the focuser at the real zero, the end of the travel through all the length of the tube each time takes nearly the same number of steps, so I assume that the initial position for the focusing procedure will also be nearly the same each time.

As I wrote, I'm going to compare the linear algorithm with the polynomial one.

Martha

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