To calculate the mid exposure time:
The average time at
witch an object is exposed (mid exposure time), is increasing with
every line of the image. (form the west to the east) To calculate the
mid exposure time: M=S*L - E/2 + T1 ;
M=mid exposure time,
S=shiftime (read out rate, time to read out one line), L=line number,
E=effective exposure time, T1= time at the start of the image. This
formula is not valid for the ramping at the start (or end, if, after
closing the shutter, the rest of the lines is read in) of the image .
The shiftime is stored in the file info like: Note = Sekunden je
Reihe 0.171, Version 1.8 of SCAN adds a 'Shiftime' item to the file
info like: Shiftime = 0.171. WinScan can use fits file format and adds
a SHIFTIME item to the file header. The effective exposure time(E) is
calculated (not for the ramping) by: E=Lccd*S
Lccd= lines on the
CCD in the current binning mode, S=shiftime. This formula is not
valid for the ramping at the start of the image( For the ramping it
is: E=L*S/2 ) The effective exposure time (E=Lccd*S) is stored in the
file info at Exposure = 80.123 (Or in fits files in EXPTIME and
EXPOSURE ) Using the effective exposure time and
the shiftime, the number of lines of the CCD in the current binning
can be calculated: Lccd=E/S
The mid exposure time can be also
calculated by ViewScan pressing with the right mouse button on an
object and choosing "Mid Exposure Time".
The time and date, in fits files:
DATE-OBS= '2002-12-29T22:47:42.54' / UTdate of integration
If the file is sliced in ViewScan, the time and date are calculated new,
so the time and date in the slices are always the time and date
the first line of the slice was read out from the active image area of the CCD.