Assertion: eyepiece's lens | /r/HasProperty | inserted into the end of the tube
Facets:
Source sentences:
text: A standard Barlow lens is housed in a tube that is one Barlow focal-length long, so that a focusing lens inserted into the end of the tube will be separated from the Barlow lens at the other end by one Barlow focal-length, and hence produce a 2x magnification over and above what the eyepiece would have produced alone.