Quote:
Originally Posted by clive milne
Peter,
As a vendor, I think it is incumbent upon you to include data on the focal ratio limit that these filters will actually offer an improvement over a 3nm (or even 10nm) passband filter.
2c
~c
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First up, This was never intended as a commercial post.
I was contacted by a filter OEM in the USA who has the capability to make ultra-narrow band filters...the likes of which I've not seen before, and would like to use myself.
The rub was, a minimum production run which would make incredibly costly
for just 3 filters.
I'm still waiting on the final specs myself, but yes, I take your point with convergent light cones there is likely to be a flattening of the bandpass curve. (also makes SII problematic)
That said, for anyone who have not used ultra-narrow band filters, there is a a chalk and cheeze difference between 3nm and 10nm filters, regardless of f-ratio. (AstroDon's web site has some nice examples)