Spherical abberation is usually caused by an undercorrected mirror. The TDE would have to be wicked to produce a "halo". Try masking-off the TDE with a cardboard annulus and see if the image improves. If it does, it's back to the barrel for refiguring. A deep center sounds like overcorrection, but if this zone is on the small side, and the rest of the mirror is undercorrected, it may still be undercorrected overall. The center would be masked by the secondary silhouette. Also, make sure your secondary is truly flat and mounted free of strain. --- DunnDave@aol.com wrote:
If I remember correctly, the figure on this mirror has a deep center and a little TDE. What causes spherical abberation?
Dave
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