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Hi all,
For those thinking about buying a filter and you only wish to start with 1 filter the best choice is easily the DGM Optics NPB filter. This is made by Omega Optical and also sold under their own name. It is a narrowband filter (UHC) but has a very tight bandpass, compared to some other narrowband filters. It allows the H-Beta Line at 486nm and allows both OIII lines at 496nm and 501nm. It works exceptionally well in telescopes of all apertures and works on a very extensive range of objects. I have countless filters but if I was limited to one filter only I would take this one each and every time.
Cheers,
John B
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