Trouble-shooting and Analysis

Calibration and "First Use" Problems

If you are just starting to use PHD2 or are connecting to new equipment for the first time, you may have trouble getting the guider calibration done.  This problem usually takes one of two forms, each requiring different responses:
  1. The star moves during calibration but it moves "too far" or "too little."  This is easy to fix - simply adjust the 'calibration step-size' parameter in the 'Mount' tab of Advanced Settings. The help content there describes how this parameter is used, and you should be able to resolve the problem quickly.
  2. The star doesn't move at all or it moves only very small amounts and in unpredictable ways.  Actually, the small movements in this scenario are often the result of seeing deflections and the mount isn't really moving at all.  Dealing with this sort of problem is described next.
In nearly all cases, the "no movement" problem is caused by failures in the hardware or, even more likely, problems in the cabling and connections.  The best tool for trouble-shooting this is the 'Manual Guide' option under the 'Tools' menu, as described in the Tools section of this help document.  Simply use the directional controls in the 'Manual Guide' window to send commands directly to the mount.  If the mount does not respond, you know you have either hardware or connectivity problems to resolve - nothing to do with PHD2.  If you're using a Shoestring device to connect to the mount, watch its indicator lights to see if the commands are reaching it.  Similarly, your ST-4 compatible guide camera may have indicator lights to show when guide commands are being received.  If you're using an ASCOM connection to the mount, be sure the COM port assignments are correct.  You can also use some of the ASCOM-supplied tools like POTH to be sure the ASCOM driver is communicating correctly with the mount.

Calibration Sanity-Checks
It is also possible that the calibration process will complete but PHD2 will post a "calibration sanity-check" alert message saying that some of the results are questionable.  This "sanity check" dialog will show an explanation of the issue and some details of the calibration results:



In the initial release (2.4.0), there are four things checked by PHD2:
With any of these alerts, the relevant data field will be highlighted based on the type of message.  You can choose to ignore the warning ('Accept calibration'), re-run the calibration ('Discard calibration'), or restore your last good calibration ('Restore old calibration').  With the third option, you can defer calibration until later and start guiding with your last good calibration data.  If you see repeated alerts on the same topic and are convinced there really isn't  a problem, you can use the 'don't show' checkbox to block future alerts of that type.

Program "Hangs" and Camera Download Problems

In some cases, you may experience problems where guider images aren't downloaded or displayed.  In extreme cases, this may even cause PHD2 or other camera-related applications to be non-responsive (i.e. to "hang").  Again, this is almost always due to hardware, camera driver, or connectivity issues, with one of the most common culprits being a faulty USB cable or device.  It is highly unlikely to be caused by an application like PHD2, so you should begin your investigation at the lower levels of the system. You can start by confirming that the guide camera is working - try using a short, direct cable from the camera to the computer and taking exposures with the "native" or test application that came with the camera.  If the camera is functional, you can start moving "upstream" by looking at USB hubs and cables, swapping them one at a time to see if you can isolate the problem.  It's worth remembering that we work in a "hostile environment" while doing our imaging, and many of the components we use are not designed for cold, outdoor conditions. So something that worked just last week or last month may no longer be reliable.

Poor Guiding Performance

Once you've gotten everything running, you will probably get reasonably good guiding results almost immediately.  You will have to decide what "good enough" means, and everyone's standard is likely to be different.  But if you find your imaging results are not acceptable because the stars are streaked or elongated, you'll need to take a systematic approach to correcting the problems.  This can be a complex task and not something to be covered here.  However, you can get help on the web from a variety of sources, with the document by Craig Stark being one of the best:  
http://www.cloudynights.com/page/articles/cat/fishing-for-photons/what-to-do-when-phd-guiding-isnt-push-here-dummy-r2677.

Log Analysis

Any sort of problem isolation or "tuning" will invariably require use of the PHD2 log files.  Both are formatted for straightforward interpretation by a human reader, and the guide log is constructed to enable easy import into other applications.  As mentioned in the 'Advanced Settings' section, applications such as PHDLab or Excel can be used to visualize overall performance, compute performance statistics, and scrutinize time periods when guiding was problematic.  With Excel or similar applications, simply specify that the guide log uses a comma as a column separator.

Guiding Log Contents

The contents of the guiding log will continue to evolve as new capabilities are added.  But the basic content is stable, and considerable care is taken to not "break" applications that parse it.  If you wish to analyze the log yourself, the following information will be helpful.  

The PHD2 guide log will contain zero or more sequences of calibration and zero or more sequences of guiding.  Each of these "sections" has a header that provides most of the information about the guiding algorithms being used and the internal parameters used by PHD2 for guiding.  At the start of either a calibration run or a guiding sequence, the last line of the header information defines a set of column headings.   The meanings of those columns are shown below:

 Calibration columns:

 Guiding columns:

All "distance" values are in units of pixels.  The header for the guiding section will show the image scale as it is known by PHD2, and that can be used to scale the pixel distance values into units of arc-seconds if desired.

Problem Reporting

If you encounter application problems that are specific to PHD2, you are encouraged to report them to the open-phd-guiding Google group: https://groups.google.com/forum/?fromgroups=#!forum/open-phd-guiding.  Obviously, the more information you can provide, the more likely we will be able to resolve the problem.  Using the following guidelines will help in that regard:
  1. Try to reproduce the problem - if we have a clear set of steps to follow, we are more likely to find a solution quickly.  If you can reproduce it, try to reduce things to the minimum number of steps.  Remember, we won't have your hardware or computer environment when we try to reproduce it ourselves.
  2. Try to be complete about describing your configuration - operating system, equipment types, PHD2 version, etc.
  3. Attach the PHD2 debug log from the session in which you encountered the problem.  You can find the debug log in the PHD2 folder in your Documents folder. If you can't reproduce the problem, try to estimate the time of day when you first saw it - this could help us find evidence in the debug log without having to sift through hundreds of lines of output.