Quote:
Originally Posted by Manav
The H.a filter is $180.00 with FWHM being 12nm or less the bandpass can be viewed here.
The two things I'd like to know are:
1. This is parfocal with QHY9 not sure what that actually means?
2. Is 12nm reasonable or should I go lower? I'd like to do Ha imaging from my suburban area.
Take Care |
The bandpass width of a filter determines the width of the portion of the visible spectrum it admits. This becomes important if you're in light-polluted skies where you will get all sorts of other light sources showing up that you won't see, or won't see as much, in a dark sky area - like Mercury vapour, sodium, and so on. For example, the average Ha filter with a bandpass of 6-12nm will also show the NII lines at 658.4nm. If you want to be a real purist, then you would need a bandpass of 3-4nm to avoid that line.
The worse your light pollution, the narrower the bandpass should be - IMHO.
ANyone who wants a set of Orange Bright NB filters should PM me or check the ads below.
Peter