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It is possible to create tracking error (TE) curve directly from TDM, without star tracking test recorded during your night shift.
Just for info: Periodic Error (PE) is an uninterpretable expression using TDM; this is why "Tracking Error" (TE) can be used for the similar (but never more periodical) tracking deviations.
You can follow this description below to to draw TE curve or use log file in other application or you can download a short program called TDM Monitor to make these steps without user interactions.
Understanding Serial Port Codes
In this document, you can see the instructions about Telescope Drive Master (TDM) COM serial port (USART) output handle.
If TDM connected to PC via RS-232 serial port, TDM sends messages to the PC via USART serial port during RESET function (LED bars run apart and converge symmetrically) and during TDM self-test (with a few "light-messages" on LED bars). As soon as the above-mentioned self-initialization process has been completed, you can get a log-file provided by TDM during controlling period. TDM sends measured RA tracking error-value (in hexadecimal format) to the serial port in every second. 128dec = 80hex code represents zero deviation. USART always writes tracking error in 1/8" step resolution and is able to write 120 digits (±15") deviation as maximum value. You can find USART utility software (COM Port Tool Kit 3.8) on the web (http://www.compt.ru) which saves the measured data into the file „compt.dat". These data can be presented as a Tracking Error curve in Excel. (The so called "Periodic Error" curve or expression is not usable with TDM because there is no obvious periodicity of the tracking errors any more.)
As explained above, during self test, TDM sends different messages to the PC about test-status via USART which can be found in the next list. (The very last message of the self test will be 2pcs of FFhexa code and error log sending starts after this code. 2pcs of FFhexa code will also be exported after reset again.)
See USART codes applied here. (Special hexa codes: 0xh = comment; Fxh = FALSE (FAULT); FFh = Reset)
00h self-test step1 starts
01h track direction positive, tracking speed good
02h track direction negative, tracking speed good
F1h tracking too fast
F2h tracking too slow
03h track display starts 1sec
04h self-test step2 starts
05h East relay direction good
06h East relay direction wrong, East relay direction swap and self-test step2 restarts
F3h -
F4h East relay timeout (relay slow or not connected)
F5h -
F6h -
07h self-test step3 starts
08h West relay direction good
F7h West relay direction wrong (impossible error: East and West relays moved in the same direction)
F8h West relay timeout (relay slow or not connected)
09h East relay return correction starts
0Ah East relay return correction ends
F9h West relay timeout (relay slow or not connected)
0Bh -
0Ch -
0Dh -
0Eh PED mode (Periodic Error Display) starts (East AND West relays wrong, probably NO guider port cable)
0Fh Tracking mode, (Tracking Error Correction), TDM tracking control Start
FAh West relay wrong, East relay good (cable broken)
FBh West relay good, East relay wrong (cable broken)
FCh -
FDh -
FEh -
FFh TDM Reset has run
Detailed description of PC display print-screens creating Tracking Curve in Excel
Connect TDM to PC with Windows OS via USART port. Use attached RS232 serial cable.
Download and install COM_PORT_TOOLKIT ver.3.8 software from its website. The installation file is: compt38_setup.exe
Start COM_PORT_TOOLKIT with compt.exe file; you have to select COM port and set parameters to TDM communications.
Adjust received parameters with PREFERENCES/TERMINAL-LISTEN menu.
Set "Byte per line" parameter in Capture menu to 1 byte/line.
Do not modify LOG parameters.
Do not modify these general preferences.
You can start capture messages from USART port by pushing "Open port" green button on the display. Switch TDM on after launching telescope tracking drive motor only! You will see TDM self-test pattern on the display and, after the last test byte, track error values are received every second.
If you want to stop USART dataflow receiving, please use "Close port" red button. (If you want to restart USART dataflow receiving, use "Clear input window" button.)
Keeping left mouse button pushed please select all data or parts of data lines you need. Using right mouse button select "Save As..."
Save the selected data in "Text file" format.
You can check saved data by opening txt file in Notepad. You will find data counter (ID) number in the first column. In the second column, you can find the capture-time from TDM in "hour:minute:second" (with milliseconds) format. The third column contains the hexadecimal value as the "message" requested. (During tracking, 80hex value means zero tracking error. Fourth column shows the ASCii code of certain character values.
Please start Microsoft Excel application. You have to activate hexa-to-decimal converter function, with "Tools / Add-Ins / Analysis ToolPak".
Using "Open" menu please find and select the previously recorded TDM data txt file to open it.
At the first step of "Text Import Wizard" menu, use "Fixed width" format.
In the second step of data conversion, you can check the four isolated columns of data.
To complete adjustment of conversion format, select "General" column data format and push "Finish" button.
Excel opens an empty sheet and fills it in using your data. Please click on the first cell of the fifth (empty) column (E1).
Write the hexa-dec conversion function "=HEX2DEC(C1)" into that cell.
Select "E1" cell and catch its right-bottom corner pushing left mouse button and pull down over the empty "E" column. Excel's auto-fill function will read hexadecimal data from "C" column and writes converted decimal data into the cells of "E" column.
Push the left button of your mouse above "E" data column on the sheet's header selecting decimal values to display. Click on "Graph" icon and choose "Line" icon as "Chart type" as the 1st step of "Chart Wizard".
As Step 2 of the wizard, you can select a sub-range of decimal values if you want and just click on "Next" button.
Step 3 - Here you can provide an appropriate title of the chart as far as X and Y values. Click Next button.
As the last step of this wizard, you can select the location of your chart. Click "Finish" button.
Tracking error curve measured by TDM will be displayed. Do not forget: the first part of the curve displayed shows the TDM's self-test trips! (See USART codes.)
Clicking on the graph you can format grid-lines. As it has been described above, 1 digit means 1/8 arc-second so 8 digits equal to 1 arc-second error value.
When you select just a part of your data from the end of TDM self-test...
... you can adjust and view high resolution chart as detailed tracking error curve in the format as you want. There are 8 digits between two horizontal lines here which mean 1 arc-second amplitude, while you can find seconds on x-axis. These jumper settings provide "the laziest" control from TDM.
Please, do not forget: you can easily adjust tracking correction setup by TDM jumper-switches!!! The best setup highly depends on the type of your mount, the driver of your mount, windy weather, etc. (See details in the User's Guide.)
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