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HOW TO USE
Star Shooting
C
Custom Mode
Solar Tracking Mode/ Lunar Tracking Mode
Difference from the diurnal motion of stars
Since the sun and moon appear to move across the sky at a different speed than
the stars, the POLARIE U includes Solar and Lunar rates option. (Remember that
the solar tracking rate is slower than sidereal time, and the solar tracking rate is
faster than the lunar rate.) These rates are useful especially during an eclipse,
allowing the user to maintain constant tracking on the sun or moon for long hours.
This mode is for time�lapse photography and it allows you to enter your desired
tracking speed (up to ten times of the sidereal rate is recommended) into the
PORARIE U. Your tracking speed setting is saved. The initial setting is four times
of the sidereal rate. If you change the setting for a different speed, a smartphone
or other wireless device and application software are needed.
Start shooting with releasing the shutter on the camera.
If the camera has an image stabilization function, make sure that the function is
turned OFF before you start photographing. It is recommended to use a shutter
release cable to avoid shaking.
The position of the same star you see in the same time moves toward west
everyday and returns to the same position in one year. Since the star sets earlier
than the sun sets, the duirnal motion of the star appears to be fast by one more
rotation than that of the sun in a year.
Because one year is 365.25 days (0.25 day is for compensating leap year), speed
of the stars based on the speed of the sun is 1 + (1/365.25) = 1.0027 rotation per
day.
The position of the moon you see in the same time moves toward east everyday
and returns to almost the same position in 29.5 days. Since the moon sets later
than the sun sets, the rotation of the moon appears to be slow by one less rotation
in 29.5 days than that of the sun. So, speed of the moon based on the speed of
the sun is 1 � (1/29.5) = 0.966 rotation per day.
Therefore, difference of the speed is 1.0027 � 0.966 = 0.0367 rotation per day (one
rotation = 24 hours). In one hour, its difference comes to
(360/24) x 0.0367 = 0.55 degrees. This is nearly the same as the moon’s angular
diameter (about 0.50 egrees).
