Quote:
Originally Posted by alpal
Hi Mark,
then why do people pay megabucks for obstructed RC telescopes with published high Strehl ratios?
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To guarantee optical and mechanical quality. 0.5 wave spherical aberration plus a 50% obstruction will probably have an Encircled Energy Ratio ( the Strehl value taking into account obstructive effects ) of less than 0.5... A low Strehl value does not render a telescope useless for imaging. Most of the worlds large RC's probably have 50% obstructions...their resolutions even with large obstruction are way below the seeing limit anyway.