The "Time Stamp Form" can be used to
evaluate the time stamp data and to check the accuracy of the
The Time Stamp Data is stored in the memory, while a drift scan image, a speckle image, a fast scan image or a sub array image is taken.
There is stored the time stamp data from a maximum number of lines, you can set in "Settings Computer" but it can be taken images with more lines.
It is stored the time, a line is read out form the CCD.
The time at the start of the image is 0 .
To show the data in the ListBox, press "Show Data".
To calculate the standard deviation press "Calculate standard deviation".
The data can be also saved to a file.
To save the ListBox, as it is shown, chose: File , Save ListBox to file
To save the raw data chose: File, Save raw data to file.
To load the data from an older image chose: File, load raw data from file.
The saved files are text files and can be read in by other programs.
The decimal separator in the ListBox can be changed. (affects only the ListBox and storing the raw data in this form, in the rest of the program the decimal separator is ".", outside this program there may be also an other decimal separator )
The column separator can be used to separate the columns in the ListBox. If the data saved form the ListBox is read in form example by excel, decimal separator "." and column separator "tab" should work.
Scale is used to show / save the data in seconds, milliseconds or microseconds.
The "Hide" button will hide the form.
The Edit field "Time per line (should be)" shows the time per line, as set in the Settings Form
The Edit field "mean + 3*sigma (in sec) (Calculate standard deviation)" shows "mean + 3*sigma " after pressing "Calculate standard deviation".
This value can be copied and pasted in the "Time per line in s " (Shiftime) Edit field in the Settings Form
Only drift scan images: If the fist lines (ramping) are not stored, when taking a drift scan image, ("store fist xxx lines" is not checked) the fist timestamp data will be stored, when the first line is stored. If the last lines are read in, ("read last xxx lines" is checked), for that last lines, there is stored no timestamp data, as this lines are read in at closed shutter as fast as possible.
Examples, format of the data:
Drift scan image, fast scan image:
time in ms :
Line Time Difference Error (mean) Error(whole)
Line: the number of the line, first line is line number "0"
Time: the time the line is read out.
Difference = TimeLine[n] - TimeLine[n-1];
Error(mean) First the mean time to read out a line is calculated.
Error(mean)=mean - Difference;
Error(whole) The whole error.
Error(whole) = TimeLine[n] - n * Shiftime;
Shifttime is "Time per line in s" set in the Settings Form.
Like the data of a drift scan image, but a new frame is indicated with "n"
Sub frame image:
B indicates the begin of a sub frame
E indicates the end of a sub frame
In the next column the number of the sub frame is stored.
Then the time is stored.
Then the difference of the time and the time in the last line is stored
The difference in a "B" line is the time it takes to shift the lines one sub frame, if this time is to large, you will get some streaking. To avoid that, the tracking CCD should be used.
The difference in a "E" line is the time the sub frame is exposed
There are taken more sub frames as fits on the CCD to avoid effects by opening the Shutter, but of course there are only stored the last sub frames which fits on the CCD.
Effect of the accuracy of the timing in drift scan images:
Taking a drift scam image, every line must be read out at a definite time.
If one line is read out a little late, the next line will be read out earlier, that will be no problem
The first lines of the image may be read a little late, this will only degrade the first lines of the image.
If there are read out many lines to late, or if the necessary read out speed can not be reached, the quality of the image will degraded.
This may happen, if you use a very long focal length at 1 x 1 binning.
ST-7 > 4 m
ST-8 > 2 m
After taking an image, a message is shown, in this message you can check also if the necessary read out speed is reached.
If the focal length is to long, you will see this in the data.
Do not run a second active program, which requires processor time at the same time.
Don't select an other window, mousing should be avoided while taking an image.
It can be selected 2 x 2 binning, you will have a faster readout speed and have to read out a line half as often.
Or use the planetary mode (but this will decrease the FOV)
Disabling brake (or Esc Key) while taking an image may also increase the readout speed a little.
Viewing no control image (See: "Settings Computer") may also increase the readout speed a little.
Taking fast scan images, it should be used at "Brake(ESC) while taking an image" the "only Esc key" feature (only available at Windows 95, 98 or ME) and the image should be stored to the memory first
Using NR, 2000 or XP you may change the priority of WinScan, see: Change Priority
If you are using a fast scan image to observe lunar occultation's or so, errors in the readout times may cause errors in the pixel values, so you may use the Time Stamp File to correct wrong pixel values. But take care of the y - position of the star.