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What is A 50 year old male patient complains of heaviness of face, headache and blocked nose. Patient gives history of chronic sinusitis. Waters view x-ray was taken. If the patient’s mouth is open during x-ray, the sphenoid sinus is seen superimposed over- and explain in detail?
Waters view- 
The image receptor is placed in front of the patient and perpendicular to the midsagittal plane. The patient’s head is tilted upward so  that  the  canthomeatal  line  forms  a  37-degree  angle  with  the image receptor. If the patient’s mouth is open, the sphenoid sinus is seen superimposed over the palate.
White and Pharoah, Oral radiology, ed 7th, pg-161