Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.
There's one of these for sale on Ebay.
Has anybody used one? What is the optical quality like? How hard is it to focus?
You lose 3+ stops, but for the solar eclipse this summer, there is plenty of light! Might go well with my DA* 300mm, instead of stacking 1.4X and 2X TCs.