Shooting the pictures

How many pictures?

Depend on the HFOV : Horizontal Field of view

Short for "Horizontal Field of View". The horizontal angle in degrees that a particular image represents of the world. The wider a lens the greater the angle of view. When using a 35mm camera the HFOV is calculable from the focal length as follows:

in 35mm camera world (24x36)

if camera is used portrait
HFOV = 2 * tan-1(12 / focal_length)
if camera is used landscape
HFOV = 2 * tan-1(18 / focal_length)

From 24x36 to digital world : focal length multiplier (around 1.5, 1.6 usually)

Use fovCalculator

Depend on the overlapping : around 30%

Look into the visor for 1/3 overlapping

Note your focal and focal length multiplier for the stitching