An option to strobe the readout for fast scan images is
added. Now it will be easier to calculate the time of the
start and the end of an occultation.
GPS support to get the exact time form a GPS receiver (NEMA output) is added
A special function to take partial TDI images was added.
( it is possible to take partial TDI images without this function,
but now it is a little more comfortable.)
Dark reference lines:
In Version 2.08, only in Drift Scan images, there is subtracted a time offset
from the start exposure time because of
the dark reference lines near the readout register of the CCD.
This offset is calculated:
Offset= d * Shiftime
d= Number of dark reference lines
It is necessary to subtract this offset.
The ST-7 has 4 dark reference lines near the readout register.
A star leaves the active area before it leaves the CCD.
ViewScan calculates the mid exposure time like:
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 the first line of the image was read from the active area 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 .
When slicing images, using ViewScan, the time in the file header of the slices will be the time the first line of the
image was read out of the active area of the CCD.
For a pixel scale of 2.5 arc sec there will be an error of 0.1680*4 = 0.672 sec for a ST-7, which may be
tolerated, but the ST-10 has a dark reference of 34 lines.
Also, the hight of the ramping of a ST-10 is not only 1472 lines, but it is 1506 lines.
The active area of the ST-7 and ST-8 is higher as a standard image, which is read out by the driver.
( ST-7 active area 765 * 512 pixels, standard image read out 765 * 510 pixels,
ST-8 active area 1530 * 1024 pixels, standard image read out 1530 * 1020 pixels )
The effective exposure time for drift scan images is calculated by the hight of the active area (512 pixels ST-7).
(height * SHIFTIME)
In Standard, SubArray, FastScan or Partial TDI images there will be
subtracted no offset from the start exposure time (= time the shutter opens).
You can disable the subtraction of the offset, by checking the FastScan CheckBox
on the DriftScan Tab Sheet.
If you have taken drift scan images with WinScan Version <=2.07 and you need a very exact time,
you may correct the file header of those images.
The values for the number of dark reference lines (DumpExtra) and the
height of the CCD are stored at \set\cameras.ini.