This thread is a following of the recent previous one concerning band passes for nebula filters.
I'm looking for a filter which would be the exact contrary of an OIII filter: that is to say a filter which would block the OIII lines (and also H alpha and H beta lines), but would let all other wave lenghts to pass.
It seems such a filter has already existed (Uwe spoke about it) and it is on the website of a main German dealer, but presently out of sale.
Does someone know if it is possible to find that device, and if yes, where and how to buy it.
This kind of filter would be very useful to extract the weak central stars embedded in bright PNs.
By now, I use a solar filter which has a band pass of 15 nm around 5040 nm. This filter rubs very well the lights of PNs, but also about 1.5 visual magnitude of stars, and this is a problem for weak central stars.
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