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Old 31-01-2009, 06:59 PM
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Merlin66 (Ken)
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Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
These Ha filter units need an aperture stop to provide at least an f20 (or above) light cone to the filter. The resolution (bandwidth) of 1.2A approx is ideal for viewing prominences, but a little wide for detailed surface contrast.
A PST is cheaper.
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