Using the black donut mask and the no-cable set-up shown in the previous slide gets rid of basically all diffraction spikes, especially asymmetric spikes, approaching refractor-like stars. Even in refractors overly stretched bright stars tend to show spikes of some kind. This is a false colour image, no white light frames had been acquired.
Hutech Canon T1i(500D),C14 Hyperstar at f1.9 ISO800,Baader 7nm Ha filter,137x91sec(=3.5hours)unguided+darks,flats,bias.False colour,no white light frames.VisLimMag 3.5, Mag17.6/sq arc-sec
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