Gemara:

Avoda Zara 

Halacha:

Birchas Kohanim,  Tefillah 

Collections: R' Grunstein Duchening

References: Avoda Zara: 20A ,  Avoda Zara: 20B  

Description

While gazing/starring at the Kohanim might be prohibitted, just looking might not be, as per other areas in Halacha in which we are forbidden to "see" something, not to mention their hands might be covered by the Tallis. But as a זכר למקדש, recalling what was done in the Temple, the custom is that we don't look at all