Jared Willson said:
I frequently hear various amateur astronomers referring to certain telescopes as being, "well corrected achromats." That always made me curious...
Are there variations in commonly used glass that would matter? Without resorting to special dispersion glasses?
Thanks - Jared
I always been curious about the use of different (non special dispersion) glasses for doublet achromats, and claimed reduction in secondary color. One manufacturer/source says "The BaK1 and F2 oiled design....which uses a barium crown glass (BaK1) as opposed to a borosilicate crown glass (BK7) reduces the effects of the secondary spectrum by nearly 20 percent, resulting in a noticeable reduction in secondary color...and at only slightly increased cost." If this is the case, why don't more makers opt for this design for such a drastic reduction in CA at minimal cost? Or is this maybe NOT the case?