The OAT firmware supports the NEO6m GPS Module (e.g. Amazon Link
for determining your current location and time.
This information is useful to calculate LST (Local Sidereal Time), which
is then used to calculate the HA for the OAT. This saves you the trouble
of getting this from your phone or laptop every imaging session.
You only need to connect 4 Pins from the GPS module to the Arduino Mega.
(on the LCD there are still 2 ground and one 5V free)
There is a combined GPS and Digital Level mounting part that
replaces the bubble level.