The easiest alternative is to buy ($150) or use a free trial of
CCDware PEMProsoftware, and follow the instructions.
Alternatively, if you just want a ballpark number, or are very good at Excel and statistical analysis, you can use PHD2 software from SourceForge (free). The process is pretty much the same for both methods. Here are the steps for using PHD2 and a compatible camera:
1. Set up mount, scope and camera. Use the PHD2 camera at the imaging position for most accurate results, but if you must use a guide scope that will work too, however, problems are often related to differential flexture which cannot be diagnosed using a guide scope. If you think you have flexture problems you can compare result from the imaging position and the guiding position.
2. Do the best polar alignment you can. PHD2 has a good polar alignment utility that can help.
3. Point the scope to a bright star in an orientation that you wish to test. Most mounts a worst near zenith. Atmosphere causes measurement errors near the horizons. 45 degs elevation and to the south is often a good choice although that is the best performance orientation for most mounts.
4. Find a bright star and place it in the middle of the camera field. There is a bulls-eye overlay in PHD2. The shorter the exposure time the better the data so a bright star and 1s exposures or less are best. Short exposures let you diagnose high frequency problems.
5. Make sure your scope (FL) and camera (pixel size) data is correct in PHD2. Set PHD2 up for guiding and do a calibration. This is necessary to tell PHD2 the directions of RA and DEC in your guide camera field. You do not need to use the ST-4 connection if you camera does not support it. Instead you can use the ASCOM pulse guiding command to the Celestron ASCOM driver. I mention this because some people use their imaging camera if they are not using OAG and don't want to swap the guide camera to the imaging position.
6. Go into set up and turn off guide commands (Brain icon, Advanced Setup Window, Mount Tab, uncheck Enable Guiding Output). Turn on logging (Tools menu, check Enable Guide Log).
7. Restart guiding, and let it run for at least 10m, longer is better, or until the star drifts off out of the camera's field. If the star does drift away, it means that you had a very bad polar alignment. Having several cycles of the ring gear lets you average out errors like wind.
8. Stop guiding. Stop logging. Make sure the log file is good by opening it in a text editor (Notepad if you are using Windows or Word). The log file is a text file. You now have data for the scope tracking performance without guiding. Read the log. Often this is enough information for you to make a decision.
There used to be a PHDlog utility that would read PHD log files and plot them, but I don't think it is on the web any more. This is where you need to know statistical analysis or get PEMPro. You can use Excel to plot and evaluate the data, however, you will need to be pretty good at Excel and data analysis. I can't give you step by step instructions here because it won't make sense unless you have some stats theory. In Excel you can:
* Convert the text table into a column format.
* You can plot the RA and DEC data relative to time.
* Use Excel's data analysis package to detrend the data using regression analysis.
