Given the following things things I've read recently;
- Apparently you can't trust parfocal filters to be truly parfocal, so you must check focus at each filter change.
Astrodons cost more because they are less prone to reflections
Reflections are more likely in narrowband than LRGB imaging (is this true?)
You can achieve quite marked results by adding a single narrowband to your LRGB images.
I wonder if a decent strategy for quality results with monochrome imagers would be to get cheaper LRGB filters from say, Astronomik, and go for a single NB Astrodon in Ha or OIII.
What do you think?
Markus