Thread: Which 8" Ritchey-Chretien F6 F8 or F9
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  #7  
Old 29-06-2009, 01:49 PM
TrevorW
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TrevorW is offline 		 
Join Date: Aug 2006
Location: Western Australia
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If i remember rightly the Orion uses BK7 glass for the primary whereas the GSO is quartz

Regards
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