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I read different opinions on whether one has IR or non IR luminance images.

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Generally you want IR blocking if you use a refractor. Don Goldman has a good article on using IR here.

I went through 2 sets of CS filter with my ST10, but both sets had light leaks and I switched to Astrodons and use Astrodons with my STL11K as well. The ST10 is much weaker in blue and with the CS filters I had to shoot twice as much blue as R&G. With the Astrodons I shoot the same amount of blue as R&G.

The CS and Astrodons I've used were close to parafocal, but not quite. What I do is focus with clear and then use an offset for the different filters so I don't refocus, just move the focuser a tad.

Don Goldman posted some interesting info on parafocal filters on the Yahoo SBIG group here

One thing to keep in mind, a shorter FR means a narrower zone of focus which will make the filters less parafocal than longer FRs.

I still use a CS Ha filter with my ST10. It's focus is quite a bit different that my LRGB filters (both the CS and Astrodons). I use an Astrodon Ha filter with my STL11K and it is very close to the Astrodon LRGB filters which is nice.

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deanrowe.net/astro
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