The cross-staff was used for siting for navigation, building construction and surveying, but I thought this illustration by Robert Fludd was interesting because he is specifically linking the use of the staff to observe stars for the purpose of horoscopy.
It's too late for the VMS, Fudd lived around the same time as John Dee's children, but I was able to confirm that he took a number of his ideas from earlier ones (although the exemplars can be hard to find, researchers mention the source-persons without mentioning the sources), so even though it's later, I thought it was worth posting as a visual link between the cross-staff and astrology:
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It's too late for the VMS, Fudd lived around the same time as John Dee's children, but I was able to confirm that he took a number of his ideas from earlier ones (although the exemplars can be hard to find, researchers mention the source-persons without mentioning the sources), so even though it's later, I thought it was worth posting as a visual link between the cross-staff and astrology: