About: http://webisa.webdatacommons.org/443572488

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	When I did this more than ten years ago I thought I would invented the configuration - but there is a version with much thicker glass (expensive) in telescope-optics.com.I used 6mm plate glass for the correctors.
http://www.w3.org/ns/prov#wasQuotedFrom	cloudynights.com