[doug mc]

Thought you might be interested in this post taken from a CN member. Having owned one of these filters for visual only, i found it always cleaned up whatever i was looking at. It imparts the least yellowing than the other filters here, while removing about the same amount of colour fringing. To remove the yellowing effect of this filter, Baader introduced the Semi Apo filter which cuts into the yellow area of the spectrum to balance the colour, at the expense of light throughput.