Speckle imaging with SCAN 1.8 and a ST-7 or ST-8 See also: readme.txt Content: 1)-Settings: 2)-Take a Speckle image: 3)-After the image is started: 4)-Limitations: 5)-Principe: 6)-Reducing the readout time: 7)-Examples for the readout time: 8)-Using the Speckle mode for drift scanning observing occultation's: 9) Using the Speckle mode for drift scan imaging 10)- Author of SCAN For this application (Speckle mode), SCAN must run in the DOS-Mode or under DOS, not under Windows!! A Pentium or compatible is required! Taking drift scan images, (4 main menu) the program may run under windows. ------------------------------------------------------- 1)-Settings: Change the following settings: Menu Settings: 1 Imaging CCD or Tracking CCD set to Tracking CCD 3 Binning should be 1x1 16 Set screen mode should be 320 * 200 33 clock cycle counter Pentium use the clock cycle counter 34 Pentium, CPU frequency set the frequency of the CPU, use the program form my homepage to test the frequency 35 Planetary mode,start,maxlength start to the position left of the star maxlenght should be about 10 Look for hot pixels, and chose the start position so, that there are no hot pixels in the sub frame. 36 Speckle imaging,HeightSubFrame set to about 10 37 NumberOfSubFrames about 1000 or much more 38 Exposure Time Sub Frame sec should be about 0.03 sec 39 Readout time line Sub Frame should be about 0.001 - 0.0015 sec test for minimum readout time: Set Readout time to 0.0001 (not 0 ) take a Speckle image and read the message at the end of the image, to change the readout time for one line of the Sub Frame then press 'y' after asked. If the size of the sub frame, the start position or other settings are changed, start a new test. 40 Use XMS (extended memory) Set this to 1, if the XMS memory should be used. Using XMS no time for storing the lines to the hard disk is required. For Speckle imaging there may be only a low gain, as the lines are stored during the exposure of the sub frames. Using the Speckle mode for observing occultation's, ( setting 38 Exposure time Sub Frame to 0 ) this may be useful. Using XMS the size of the hole image is limited by the available XMS. Using XMS, the Speckle mode may be also used for drift scan images, filling in the calculated time at 39 and set Setting 38 to 0. I tested XMS in the DOS mode only on my computer. If there are error messages related to XMS, restart the computer, check the Settings, maybe you reduce the number of Sub Frames or disable XMS. 41 Use XMS for time stamp file If this is disabled, there are only stored information's about the readout time of the first 4000 lines ( The image file may still have more than 4000 lines) Information's are in micro sec. (0.000001sec) If this is enabled, there are stored information's about more lines ( all lines of the image or as much as fit in the XMS). Information's are stored in micro sec with decimals. The time stamp file may be very large! If 40 Use XMS is disabled, 41 is also disabled (ignored). The other settings should be the same as for standard / drift scan images. Settings number: 2,6,7,18,21 are ignored Settings number: 9,15,17,30,31,32 are disabled. Settings 4,5: the CCD should be cooled, hot pixels may look like stars. The Settings for Speckle imaging in 36,37,38,39,40,41 will not affect standard / drift scan images. ------------------------------------------------------- 2)-Take a Speckle image (Speckle mode) In the main menu: 40 Take a Speckle image read the messages, shown by the program, put in a file name without extension, then the image is taken 41 Take a Speckle image a dark frame (shutter closed) to do a dark subtraction with an other image processing software ( SCAN does not support in time dark subtraction taking Speckle images ) ------------------------------------------------------- 3)-After the image is started: At the screen a control image is shown. There are shown many sub frames at the left side of the screen, being updated form the top to the bottom. If the star you want to picture is not visible, you can shift the start of the sub frames left or right using the cursor keys.(this may affect the timing) The sub frame can also be zoomed using Ctrl + cursor keys. (only for tests, finding stars, or so, this destroys the file !!!, start a new image after zooming) (zooming also affects timing) Pressing 'z' the sub frame will be set to 10 x 10 pixels zooming destroys the current file. Start a new image after zooming. You can stop the exposure, pressing ESC. Pressing 'c' disables the control image, pressing space enables the control image, pressing 'b' resets the background. ( the program uses an autocontrast function on a per line basis, related to the background of the brightest line) The image (*.st7) is stored on the hard disk. ( directory /picture ) A file with the extension *.t7t (a text file) is also stored there . You can view it, to control the settings. A time stamp file is stored in the directory /tstamp . All entries in micro sec. (only Speckle mode, entries for drift scan images are still in milli sec ) It is used, to control the accuracy of the timing. If the timing is not precise enough, increase the readout time for one line (Settings, 39 ) ( See also the message at the end of an image) In the image you will see many sub frames with the chosen height and width. In every sub frame the star is pictured. Some streaking is also visible. ------------------------------------------------------- 4)-Limitations: Without using XMS: Max pixel number of one sub frame: 1500 but it should be about 10x10=100 Max width of a sub frame/line: 500 should be 10 Using XMS: No limits for the size of the sub frame. The size of the whole image is limited by the size of the XMS. Accuracy of the timing: about +-4 micro sec Readout time for one line of a sub frame: about 800-1500 micro sec (0.0015 sec) The exposure time sub frame (Settings 38) Should be about 0.03 sec must be a multiple of the readout time for one line (it will be rounded, if set to an other value) (reason for this lies in the kind of implementing this feature to SCAN) In time darksubtract and flat field correction are disabled. Auto Dice/Auto Grab is disabled. Reading out rest of the lines on the CCD (Settings 15) is disabled (because not useful). It should be used only the Tracking CCD, because the imaging CCD is to slow. (readout time) In the time stamp file, there are made only up to 4000 entries(lines), if XMS is disabled, but the image may have more than 4000 lines. It should be used the planetary mode, the sub frame should not be to big. (should be about 10 x 10 ) A Pentium or compatible is required. The clock cycle counter must be used (Settings 33) The 320 x 200 screen mode should be preferred (faster) ------------------------------------------------------- 5)-Principe: The shutter is opened , the exposure is started. After about 30 milli sec there are read out about 10 lines (height of the sub frame) The lines are read out at definite times (readout time for one line about 800-1500 micro sec ) 10 lines will last about 8 - 15 milli sec. There are read out as many sub frames as you want. (using XMS as many as fit in the XMS ) The image may be evaluated with other image processing software. With other software you may do dark subtraction or flat field correction. ------------------------------------------------------- 6)-Reducing the readout time: The readout time depends from: Windows or DOS: DOS (or DOS-Mode)is faster , use only DOS(or DOS-Mode)! Width of the sub frame: (maxlenght, Settings 35) should not be to wide, use planetary mode Start of the sub frame (Settings 35 ) the readout time will decrease when the start position is increased ( Position should be set at the right side of the CCD, but not at the right border, because the star than may leave the CCD, and you can not shift the sub frame, using the cursor keys ) ( This correlation is only valid for the tracking CCD, at the imaging CCD the readout time will increase when the start position is increased) Screen mode (Settings 16) Mode 1, 320 x 200 pixels is faster than 640 x 480 pixels the control image may be shut of pressing 'c' after starting the exposure, that will reduce the readout time a little more, but then you can not control, if the star leaves the sub frame Tracking / imaging CCD the tracking CCD is much faster than the imaging CCD The imaging CCD of the ST-7 is faster as the imaging CCD of the ST-8 Binning 1 x 1 binning is faster than 2 x 2 binning ( As you want a high resolution 1 x 1 binning should be preferred in every case ) Exposure Time Sub Frame sec If this is set to 0 , it will also affect the readout time as the lines are stored during the exposure of the sub frame. If XMS is enabled, this will not effect the readout time. If it is set to 0, line after line is read out with the readout time line sub frame. 38 Exposure Time Sub Frame sec should be about 0.03 sec The height of the sub frame does not effect the readout speed of one line in most cases. (the time to read out one sub frame will increase, but the brightness of the streaking should be constant) ------------------------------------------------------- 7)-Examples of the readout time: This may vary on other computer systems. Readout time in micro sec: Calculated by mean(ReadOutTime)+3*StandardDevation(ReadOutTime) (See the message at the end of the image) (The readouttime was set at 39 Readout time line Sub Frame to a low value like 0.0001 sec (100 micro sec) (not to 0 ) ) Start of the Sub Frame: Screen mode 1, 320 x 200 1x1 binning Width of the sub frame 10 pixels Start position of a sub frame - readout time micro sec 1 - 1390 50 - 1250 100 - 1084 150 - 916 180 - 817 Width of the Sub Frame: Screen mode 1, 320 x 200 1x1 binning Start position at 100 Width of the sub frame - readout time micro sec 5 -819 10 - 1084 20 - 1382 40 - 1980 80 - 3170 Binning: Screen mode 1, 320 x 200 Start position at 100 Width of the sub frame 10 micro sec 1x1 binning - 1084 2x2 binning - 1335 (Start position at 50) Tacking / imaging CCD: Screen mode 1, 320 x 200 Start position at 1 Width of the sub frame 10 micro sec tracking CCD - 1390 imaging CCD - 6166 Screen mode: 1x1 binning Width of the sub frame 10 pixels Start position of a sub frame 180 micro sec Screen mode 1, 320 x 200 - 817 Screen mode 2, 640 x 480 - 1200 screen shut of, pressing 'c' after starting the exposure - 768 ------------------------------------------------------- 8)-Using the Speckle mode for drift scanning observing occultation's: This mode can also be used observing occultation's of a star by an asteroid with a height readout speed. ( The telescope dirve is on) (There may be other applications like checking the seeing) The readout times in the time stamp file will be in micro sec. The "standard" drift scan mode uses no XMS. As the program may have to wait for storing line after line on the hard disk, the time may differ form line to line, (if one line is read a little late, the next is read earlier) using XMS may enable a higher accuracy of the timing. Use the same settings like described above, except: 38 Exposure Time Sub Frame sec must be set to 0. 36 Speckle imaging,HeightSubFrame should be set to about 1 NumberOfLinesToRead= HeightSubFrame*NumberOfSubFrames TimeForTheWholeImage= NumberOfLinesToRead*ReadoutTime 3 Binning, 2 x 2 binning may be also possible 39 Readout time line Sub Frame set to about 0.0008 - 0.0018 sec (1800 micro sec) test the minimum readout time. The readout time can be also adapted to the brightness of the star. 40 XMS should be used!!! No time is required for saving the lines on the hard disk Check how many lines may fit in the XMS. If XMS in not used, the value of 39 must be a little higher , as in the speckle mode,as the lines are stored during the exposure of the sub frames. (now line after line) You should not use the same testing of the readout speed, than for speckle imaging. ( At the end of the image a message is shown, showing the mean readouttime. Set the value in 39 a little higher (+5%) and try again) (In this case you can not relay on mean + 3*StandardDevation.) The readout time can be adapted to the brightness of the star. 41 Use XMS for time stamp file Check if this is necessary, the time stamp file may become very large. 9) Using the Speckle mode for drift scan imaging Is useful if you are using a long focal length and need a fast readout speed, as this mode can use XMS. (Using a drive cash program as smartdrv, or a fast defragmentated hard disk, the difference may be small) As the program may have to wait for storing line after line on the hard disk, the time may differ form line to line, (but if one line is read a little late, the next is read earlier) using XMS may enable a higher accuracy of the timing. The readout times in the time stamp file will be in micro sec. Menu Settings: 1 Imaging CCD or Tracking CCD may be Imaging CCD 3 Binning may be 1x1 16 Set screen mode should be 320 * 200 or press 'c' after starting the image. 33 clock cycle counter Pentium use the clock cycle counter 34 Pentium, CPU frequency set the frequency of the CPU, use the program form my homepage to test the frequency 35 Planetary mode,start,maxlength chose the start and maxlenght so that the readout time is fast enough 36 Speckle imaging,HeightSubFrame set to 1 37 NumberOfSubFrames image must fit in the XMS 38 Exposure Time Sub Frame sec set to 0 39 Readout time line Sub Frame fill in the value calculated by focal length, binning ... from Settings 7 test if this readout time can be reached 40 Use XMS (extended memory) Should be set to 1. As the lines are saved in the XMS, this mode may be a little faster. 41 Use XMS for time stamp file Set to 1, if necessary. 9)- Author of SCAN Christoph Flohr Osterstrasse 29 D- 30880 Laatzen eMail: Christoph.Flohr@t-online.de Homepage: www.christoph-flohr.de