phd guiding dec calibration failed

Trouble-shooting and Analysis

General guide to resolving problems, large/abrupt guide star deflections.

• Tiny movements of the various components in the guiding assembly as a result of the changing gravitational forces while the mount tracks the target object
• Dragging, binding, or snagging of cables, especially those that are connected to the guide camera
• Wind gusts or less commonly, effects from camera filter changes, auto-focusing, or mirror movement
• Use of mount features for backlash compensation - these should not be used with PHD2 guiding

Camera Timeout and 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").  This is nearly 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.

To help detect these problems and avoid “hangs”, PHD2 uses a camera timeout/retry mechanism.  This timeout value is set in the Camera tab of  Advanced Settings and uses a default value of 15 seconds.  This means that PHD2 will wait up to 15 seconds after the expected completion of the exposure to receive the image from the camera.  This is a very generous amount of time and should work well for most cameras. When the timeout occurs, PHD2 will automatically disconnect the camera and try to re-connect.   An alert message at the top of the screen will advise you of the timeout event and whether the reconnection attempt was successful.   Regardless of whether the reconnection succeeded, you have a hardware problem of some kind that needs attention.

  Here is an approach you can use to reproduce and then identify the problem:  

Make sure you are running the latest version of PHD2 – often a development version – and the latest versions of the camera drivers.   Some of the camera vendors issue frequent software changes that must be matched by corresponding changes in the software libraries used by PHD2.   When these updates aren’t backward compatible, you have no choice but to run the latest versions of everything.

Confirm that the guide camera is basically functional - 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.

Repeat step 2 but use PHD2 as the application.   You can do this in the daytime by just connecting to the camera and looping 1-2 second exposures for a reasonably long time.   The PHD2 display will often be all-white in daytime operation, but as long as the looping continues with no error messages, things are going ok.   If you see problems in this step, it doesn’t mean it’s a PHD2 problem – it isn’t.   The difference is that PHD2 is using the camera in single-exposure mode whereas most other apps use it in video streaming mode.   The single-exposure mode involves more back-and-forth data traffic with the camera and can expose timing problems in the drivers.

If you can’t trigger a failure in step 3, add the imaging camera into the mix.   Use your imaging application to loop exposures in parallel with what PHD2 is doing.   This will help expose traffic and bandwidth problems in the USB system.

If no problems occur in step 4 over extended time periods, use the same USB cables and host computer that you were using when you first encountered problems.   If you’re already doing this, you need to consider other possibilities:

• The problem may be temperature-related – perhaps it occurs in colder nighttime conditions but not during the daytime.
• The OS may be suspending one or more of the USB ports for power-conservation.   This has become a more common problem with Windows 10 and later releases.   Use the Windows device manager and find all the entries that refer to a USB “hub” or a USB controller.   For each of these entries, open their properties dialog and click on the ‘power management’ tab.   Disable any permissions that allow the OS to suspend the device for power management reasons.
• Make sure the power source on your test computer matches that of the computer you use for imaging.   Both should be running on A/C power at this point.
• The problem may be triggered by loose cable connections on either end – the cables should not lose connectivity if the cable is moved around as it will be during imaging.

When you can replicate the timeout problem, the first place to look is the USB cable followed by the other USB components on your system.   Sources of USB-related problems include the following:

•   Low-quality or slightly damaged USB cables - in recent years, some of the camera vendors have started shipping low-quality USB cables with their cameras so you shouldn't assume the one you got with the camera will work. It’s also important to remember that we work in a hostile environment while imaging, and many of the components we use were not designed for cold, outdoor conditions. If you regularly tear down and reassemble your gear, the flexing of the cables can damage low-quality conductors. So something that worked just last week or last month may no longer be reliable.   High-quality USB cables with 24AWG conductors and lengths no greater than 15 feet are recommended.
•    USB-2 cameras and cables plugged in to USB-3 ports - t hose combinations are supposed to be backward-compatible but that’s only at the hardware level, the driver implementations can be adversely affected.
•    USB port suspension by the OS (step 5b above)
• Marginal power delivery to the guide camera - y our main imaging camera probably has its own power supply but other devices like the guide camera are typically powered via the USB cable.  Particularly with laptops and inexpensive computers, you may want to try using a powered USB hub to deliver power to the camera.   This approach may also be required when operating in cold conditions or when using cables of maximum length.
• Use a Microsoft tool (USB View) for mapping the tree structure of USB ports and USB controllers.  
• Try choosing ports that will keep your imaging and guide cameras on separate USB buses.
•   Try using a different camera driver.   Many vendors supply both an ASCOM and a native driver, so try the one you haven’t been using.   It’s not uncommon for some of the ASCOM drivers to lag the native drivers in terms of bug fixes and compatibility
• See if the problem is related to overall USB bandwidth and try to reduce the total USB usage:

Calibration and Mount Control Problems

• Mount/connectivity problems or operational mistakes:  These are the most common sources of the problem.  The best tools for trouble-shooting them are the 'Manual Guide' dialog or the Star-Cross test, both under the 'Tools' menu and 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 while watching a star in the image display window.  Use fairly large guide pulse amounts - at least several seconds - so you can clearly see if the mount is moving.  Try to move the mount in all four directions and verify the target star is moving by roughly equal amounts.  If the mount does not respond, you know you have either hardware or connectivity problems to resolve - nothing to do with PHD2 . Operationally, you cannot complete a calibration if you're pointing close to the celestial pole or if the mount isn't properly initialized, un-parked, and tracking at the sidereal rate.  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 and you've selected the correct ASCOM mount driver for your equipment.  You can use some of the ASCOM-supplied tools like POTH to be sure the ASCOM driver is communicating correctly with the mount.  It is best to use the latest version of the ASCOM driver for your mount to insure pulse-guiding support is complete.
• Incorrect calibration step-size:   If you've used the new-profile wizard and have provided correct values for focal length, camera pixel-size, and mount guide speed, the "step-size" used in calibration should already be correct. You should confirm this, however, because beginners frequently enter incorrect values for these parameters.  If you've defined or modified your profile by hand (a bad idea) or have changed guide speed settings in the mount, you may need to adjust the 'calibration step-size' parameter in the 'Guiding' tab of Advanced Settings . The help content there describes how this parameter is used, and you should be able to resolve the problem quickly.  But if you've used the new profile wizard carefully and are seeing problems with too little or no guide star movement, the problem probably lies elsewhere.

• Too few steps (shown above) - resolving this issue can be easy assuming the mount is actually working correctly.  Just adjust the calibration step-size downward until you get at least 8 steps in both the west and north calibrations.  If you used the new profile wizard to set up your configuration, a good starting value for calibration step-size will already be set. In that case, the alert suggests you entered parameters incorrectly in the new-profile-wizard or the mount guide speed has changed.  You should check these things and make sure they're right.  If you find that the number of steps in RA and Declination are substantially different,  you are probably seeing evidence of declination backlash unless you are using different guide speed settings on the two axes.
• Orthogonality error - the camera axes are normally computed independently even though they  should be perpendicular.  The angle calculations do not require great precision, but if they are significantly non-orthogonal, you should repeat the calibration.  If you see repetitive alerts of this type and the axes are significantly non-orthogonal, you need to identify the problem and fix it.  Common causes are bad polar alignment, large declination backlash, or large periodic error in RA.  Any of these problems can cause the guide star to move significantly on one axis while PHD2 is trying to measure its motion on the other axis. If you suspect these problems, go ahead and accept the calibration, then run the Guiding Assistant to measure your polar alignment error, declination backlash, and RA tracking error.  In other cases, the mount may not be moving at all, and the measured displacements of the star are just caused by seeing effects.  This sort of problem should be obvious in the calibration graph at the left of the dialog.  If the axis error is relatively small and you are convinced the hardware is working properly, you can avoid further alerts of this type by setting the option to 'Assume Dec orthogonal to RA' in the 'Guiding' tab of the Advanced Settings dialog. But you should do this only if the error is fairly small - otherwise, you are simply ignoring a serious problem.  
• Questionable RA and Dec rates - assuming the guide speeds reported by the mount are accurate, the measured guide rate for right ascension should be related to the declination guide rate by approximately a factor of cosine (Declination).  In other words, the apparent RA rate gets smaller as you move the scope closer to the pole.  PHD2 won't try to identify which rate is incorrect - it is simply alerting you that something looks wrong with the rates.  You can sanity check these rates yourself quite simply.  If you are guiding at 1X sidereal rate, your declination guide rate should be approximately 15 arc-sec/sec; with a guide rate of 0.5X sidereal, the declination rate would be 7.5 arc-sec/sec, etc.   A declination rate that is significantly smaller than the RA rate is often an indication of substantial declination backlash .  Using a calibration that triggered this alert can lead to over-shooting in Dec guiding because the actual guide rate is probably larger than the measured one.  To work around this problem, you should manually clear the Dec backlash before starting calibration.  You can do this in either of two ways: 1) make sure the mount's last slew direction was north or 2) use the hand controller to manually move the mount north ('up' arrow) at guide speed for 10-20 seconds.  
• Inconsistent results - if the calibration results are significantly different from your last-used calibration, an alert message will be generated.  This may happen because you've made a change in your configuration.  That doesn't imply a real problem, but you should probably consider creating a separate profile for the new configuration.  By doing so,  PHD2 will remember settings for each of your profiles, letting you switch between them easily.  If you haven't made a configuration change, you should determine why the results are so different.

• Set the mount guide speed to 1X sidereal.  Bring up the 'Manual Guide' tool in PHD2 and choose an initial value for 'Guide Pulse Duration' - start with, for example, 5 seconds.
• Start a 60 second exposure on the main camera.
• Send a 5-second pulse west, then two 5-second pulses east, then a final 5-second pulse west.  This should return the star to its approximate starting position.  You should wait about 5 seconds after sending each guide pulse to give the command time to complete before sending the next pulse.
• Now send a 5 second pulse north, then two 5-second pulses south, then a final 5-second pulse north.  This should again return the star to its starting position.
• Wait for the main camera image to download and see what you get.

Lost-Star Events

• The screen will flash and a "beep" tone will sound.  The sound can be disabled if you wish (Advanced Settings/Guide tab) but the screen will always flash
• No guide commands will be issued and the next guide camera exposure will be started
• Lost-star event messages will be sent to any imaging applications that are connected to PHD2
• Lost-star messages will be displayed in the status bar including the reason for the loss - low SNR, low HFD, low-mass, or mass-change

Alert Messages

Display window problems, hot-pixel and star-selection problems, restoring a working baseline.

• On the 'Algorithm' tab of the Advanced Settings dialog, you can individually reset parameters by looking at the tool-tip for each field.  Hover your mouse cursor over the field and the default value will be displayed.  Note that this is not accurate for the min-move settings, which depend on your image scale.  This approach is best when you want to restore only a few settings.
• Click the 'reset' buttons on the 'Algorithm' tab for the selected RA and Dec guide algorithms.  This is the recommended approach for resetting all the guiding parameters.  The min-move settings will be reset to the values originally calculated by the new-profile-wizard.  If you subsequently adjusted those settings by running the Guiding Assistant, you should repeat that process.
• Run the new-profile-wizard, accessed by clicking on the 'Manage Profiles' button in the 'Connection' dialog.  Use the same camera and mount choices you already have and give the profile a new name.  If you want to re-use the dark library and bad-pixel map from the old profile, connect to the new profile and use the 'Darks' menu to import those files from the old profile.  Once you are satisfied with the new profile settings, you can delete the old one.

Poor Guiding Performance 

Log analysis, guiding log contents.

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:

• dx, dy   are offsets from the starting position, in pixels, in the camera coordinate system
• x, y are the camera x/y coordinates of the guide star at the end of each calibration step
• Dist is the total distance moved in the camera coordinate system (dist = sqrt(dx*dx + dy*dy).   This is the value used by PHD2 to compute the calibration parameters
• dx, dy are the same as for calibration - offsets from the "lock position" of the guide star in the camera coordinate system
•   RARawDistance and DECRawDistance - these are the transforms of dx and dy into the mount coordinates - in other words, they use the arbitrary angle of the guide camera to map from X/Y on the camera to RA/Dec on the mount
•   RAGuideDistance and DECGuideDistance - these are the outputs from the various guiding algorithms.   The guide algorithms operate on the "raw" distances and decide how far, if any, the telescope position should be adjusted in each axis.   For example, with a "minimum move" parameter set, the "guide" distances can be zero even when the "raw" distances are non-zero.
• RADuration, RADirection, DECDuration, DECDirection - these are the values determined by the two "guide" distances above.   The "durations" are the lengths of the guide pulses, in milliseconds, needed to move the mount by the distances specified by RAGuideDistance and DECGuideDistance
• XStep, YStep - step-adjustment durations for the adaptive optics device if one is being used
• StarMass - a brightness measure of the guide star image
• SNR - an internal "star-detection ratio" used by PHD2 - essentially a measure of how well the star can be distinguished from the sky background
• ErrorCode - an integer value representing the quality of the guide star measurement:
• 0 - no error
• 1 - star is saturated
• 2 - star has low SNR
• 3 - star mass is too low for accurate measurement
• 4 - star HFD is below Min-HFD value
• 5 - star HFD is above Max-HFD value
• 6 - star has drifted too near the edge of the frame
• 7 - star mass has changed beyond the specified amount (only if mass-checking is enabled)
• 8 - unexpected error

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

• 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.
• Try to be complete about describing your configuration - operating system, equipment types, PHD2 version, etc.
• Upload  the PHD2 log files  from the session in which you encountered the problem - this is a critical step.  Use the 'Upload log files' function on the 'Help' menu to do this -- it gives you an easy way to select the relevant log files and then uploads them to our server without constraints on file size. Attaching log files to forum messages is discouraged and will often not work at all because of the file sizes.  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.  If you request help on the forum without uploading your log files, you will usually be asked to do so, thus adding an unnecessary delay in getting help.

A certain margin of error here tends to be okay. However, some items are telltale signs that something is wrong with either your equipment or a setting.

The Calibration Graph

The first thing we want to look at here is the graph on the left. This is representative of what I would consider to be a pretty good calibration.

What you are looking for is a right angle on this graph with reasonably straight lines. I have never known it to be an issue if the lines don’t match up with the X and Y axis on the graph, as long as they are straight.

On the other hand, if your calibration results look more like a scatter chart, something went wrong. In this case, you want to re-calibrate before proceeding with your guiding.

The Number of RA and Dec steps

Generally speaking, these two numbers should be between 8 and 14 steps in each direction, according to PHD2’s website.

As I mentioned, a slight margin of error is acceptable as long as it doesn’t affect your guiding. If these numbers are wildly outside of the range mentioned above, there’s a good chance your calibration will fail altogether. I will touch more on this later.

RA and Dec Rate

The numbers on your chart may not be the same as mine, as they are mainly dictated by your guide rate. My guide rate here was set to 0.50x.

If there is a major difference between the actual and expected rates, there is an issue somewhere.

Most of the time, the issue is that your guide rate in PHD2, and the guide rate in your ASCOM software don’t match. This is a problem that needs to be corrected before you proceed with your guiding.

If the difference you see is only in your Dec rate, this is likely backlash in your mount. Before you resort to opening it up and tuning it, make sure to run the Guiding Assistant.

Both of these topics are covered here in 9 tips on how to improve PHD2 guiding .

Declination

This is the declination of where my scope was pointing when I did the calibration; as you can see, mine was not within 30 degrees of the celestial equator. Whoops.

My guiding was still pretty good in this case, but it’s a good idea to stay within the PHD2 guidelines now that you know what they are.

Focal Length

This is the focal length of your guide scope.

It’s not the diameter of the guide scope, and it’s definitely not related in any way to your main scope unless you are using an off-axis guider.

If this is wrong, it’s probably going to cause the following error that I will discuss.

Calibration Failed- Star did not move enough.

If you are getting this error message, it’s likely because you have your guide scope focal length or your guide camera pixel size set incorrectly.

Both of these numbers absolutely must be correct. PHD2 needs these two numbers to calculate the image scale of your guiding equipment. It uses the image scale and the calibration distance to calculate the correct value for the calibration steps.

When these settings are wrong, the calculation for the calibration steps is also going to be incorrect. As a result, the star will likely not move enough, and your calibration will fail.

To check these settings, click on the brain in the bottom left-hand corner and click on guiding.

If you realize that your focal length is incorrect and change it, make sure you still click on advanced.

If you don’t click advanced to open the calibration calculator, it will not re-calculate the correct calibration steps. If the calibration steps are left unchanged, the problem will persist.

PHD2 is a fantastic piece of guiding software and is pretty easy to use once you have it set up correctly.

Before you can start guiding, you need to make sure that your settings are correct and calibrate properly.

The vast majority of PHD2 guiding issues are caused by one of the three following things: 

• The guide rate in PHD2 doesn’t match the ASCOM software guide rate 
• The guide scope focal length is set incorrectly 
• The guide camera pixel size is set incorrectly 

Sources: https://openphdguiding.org/man-dev/Advanced_settings.htm

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PHD Guiding help (wont calibrate)

By Mick UK August 6, 2010 in Discussions - Software

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I keep getting the following error message using PHD..it stops calibrating at 61 every time.

"phd guiding RA calibration failed star did not move enough"

any help greatly appreciated:(

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• Created 13 yr
• Last Reply 4 yr

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IvanT 9 posts

Mick UK 4 posts

SlipperySquid 3 posts

carastro 3 posts

Dec 23 2010

May 14 2011

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steppenwolf

August 6, 2010

Try clicking on the 'brain' icon and increasing the 'calibration step (ms)' figure to something around the 1500 mark - this commonly resolves the issue as it increases the amount of movement applied t

August 7, 2010

Ive had the same error message before too, and that was down to not plugging the st4 guide cable in fully... doh! I only re-calibrate if im imaging a completely different part of the sky - eg: going f

Try clicking on the 'brain' icon and increasing the 'calibration step (ms)' figure to something around the 1500 mark - this commonly resolves the issue as it increases the amount of movement applied to the mount during calibration.

Thanks Steve,

Much appreciated:)

Happened to me once when the cable came slightly out of the guide cam and it lost comms with the mount (it had a guide output). Still sent a picture to the laptop so it was really confusing.

SlipperySquid

Also had this problem mate last night! Was my first try at guiding and I spent 6 hours fiddling about and swearing! it was great.

Anyway I was having the same problem nothing I did would get it to calibrate UNTIL I looked under the MOUNT header, then I chose "on camera" I think that was it anyway!

and then it would guide! and calibrated within about 7 steps.

Another trick is to nudge the mount to the north before starting calibration. The first DEC calibration command is North and doing this takes up the backlash. With my old LX200, DEC calibration would sometimes fail if this wasn't done.

I suppose the same applies to RA, but I never had any trouble with this and can't remember which direction the first calibration move is.

I havent done any guiding before so do i assume that every time i move to a new target i will have to callibrate PHD?

Dont think you HAVE to but it's best I think.

Plus it literally takes seconds to calibrate...mine takes less than a minute now I ahve it set right!

Ive had the same error message before too, and that was down to not plugging the st4 guide cable in fully... doh!

I only re-calibrate if im imaging a completely different part of the sky - eg: going from M101 through the meridian to M31. If its just a short(ish) jump, then no need to. Good polar alignment will help a lot... oh, and choose "north" or "south"... not "auto" as you will get backlash. Choosing north/south or means that the gears only need to correct in one direction in DEC - its just a case of figuring out which way it likes to drift. For me its North on the East side of the meridian, and South for the West.

I've had similar problems in the past, the solutions in my case were (on different nights) making sure that;

The correct cables are properly connected - I tape mine into place with duct tape these days just to be sure.

The mount is correctly selected in the Mount menu - "Ascom" when I used to guide with a webcam via EQMOD and "On-Camera" now that I've got a QHY5V connected to the ST4 port on the mount.

The calibration steps long enough - mine are set to 1200mS.

I only generally re-calibrate if I move the mount to a completely field of view of the sky and I seem to get away with it most of the time.

Hope this helps

I had that error message loads of times - Steve suggestion fixed if pretty much every time.

Make sure that the wires to the scope are not snagged and that the scope is balanced (and both axis locks are locked).

• 4 months later...

I was playing with PHD tonight and couldn't get it past the North alignment step (without going into manual mode). Kept failing at 61 with "Dec calibration failed turn off Dec guiding".

I tried upping the step ms setting from 750 to 1500 to 2000 but it didn't make a difference to the North cal problem (it did make East West cal a lot faster). When calibrating it did the East, West & Backlash without a problem but I didn't any movement at all when doing North. I used the manual mode to nudge it North which got it past the calibration and it started guiding. After < 2 mins, it started beeping & I could see it was loosing tracking on the guide star.

Reading about it, a common problems seems to be poor polar alignment, so I re-checked & confirmed my drift alignment. Drift alignment kept a star pretty much in the centre of the reticule for a couple of mins before it started to drift out, so I don't think that is the problem.

My guide camera is a QHY5, any suggestions as to the settings I should use for that setup?

As usual, any help/suggestions greatly appreciated.

Have you tried removing and reinstalling the camera drivers and phd? maybe need updated ones. I'm using PHD version 1.12.0 and the latest drivers for my Orion Starshoot autoguider (nearly the same as the qhy5) and have no problems in windows 7? Just an easy idea to start on if you havent tried it already? Is there anyone you could borrow another st4 cable from to see if it is your cable?

Ivan, have you checked your DEC balance both with the scope horizontal and scope vertical, if you have too much of an inbalance then DEC won't calibrate in my experience.

Also I have a cable issue as well, corroded contacts, I replaced them with Astronomiser quality ones and never had a problem since.

I've only just recently installed it for the first time. It's ver 1.12.0 It is Win 7. Thanks for the suggestion though.

Ivan, have you checked your DEC balance both with the scope horizontal and scope vertical, if you have too much of an inbalance then DEC won't calibrate in my experience. Also I have a cable issue as well, corroded contacts, I replaced them with Astronomiser quality ones and never had a problem since.

I'll re-check it, I have it balanced with the 1000d etc in place but last night I must admit I didn't have the 1000d connected and hadn't re-adjusted the balance to compensate. Thanks for the suggestion, I give it a whirl.

I had this problem recently and it toook me ages to figure out what the problem was.

It was moisture having got into the Guide camera not giving sharp enough stars (through leaving it in the Observatory), won't make that mistake again. Duh!

The joys of trying to fathom out the cause were a real PITA.

I had this problem recently and it toook me ages to figure out what the problem was. It was moisture having got into the Guide camera not giving sharp enough stars (through leaving it in the Observatory), won't make that mistake again. Duh! The joys of trying to fathom out the cause were a real PITA.

So it was able to calibrate East West & clear Dec Backlash, but failed to calibrate North due to moisture?

The problems varied, starting with poor guiding, then deteriorated into not being able to calibrate at all, then as it was recovering (drying out) it calibrated RA but would not calibrate North Dec.

Eventually it went back to working OK with no changes made.

Hehe, bet that was a fun night :-)

Sounds like there can be lots of reasons for what appears to be a common problem. Think I've eliminated bad polar alignment, next on my list is balance and I'll keep moisture buildup in mind also.

Thank Carole

Sent from my iPhone using Tapatalk

Hehe, bet that was a fun night

It was a "fun" 3/4 weeks!!!!

I've still got some hair left!!

Checked my balance last night and and found it was quite a bit top heavy camera end of the scope. Corrected that, tried calibration again (up at 2500ms), had to nudge the scope north with my hand to to get Dec cal done.

Now don't all laugh, this may be very silly, but, should the sidereal tracking on the HC be turned on or off while guiding? With it off I found that PHD calibration worked without any intervention. After it went to guiding though, the guide star tracked off the left edge of PHD until eventually loosing tracking.

Has the tracking rate option on the HC to be set normally?

Tracking should be turned on. If it isnt, and guiding is working, the guiding should keep the stars reasonably still anyway - but guiding is intended as a correction to tracking, rather than to be used instead of.

If PHD won't calibrate, the first check is that PHD is actually talking to your mount (either via "on-camera" ST4, via ASCOM pulse guiding, or whatever). I think the way to do this is to use tools, manual guide - and then move the scope.

Just wondering... is it possible to test system to check if GPUSB is making connection etc using the simulater instead of a real camera when doing calibration? I know that the GPUSB check programme would do this but will the mount callibrate when using the simulated camera

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Calibration Failed: Star did not move enough

Joseph Kelly

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Working on improving my guiding.... Open PHD Guiding project PHD2 · Christian Bennich · ... · 46 · 980 · 6

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5 Tips for Better PHD2 Guiding

PHD2 is a telescope autoguiding software that automates the process of tracking a guide star. This is an important aspect of deep sky astrophotography because it allows you to focus on capturing successful long exposure images and get the most out of your telescope mount .

PHD2 is easy enough for a beginner to use right away, yet also includes sophisticated guiding analysis tools that experienced users will appreciate. The software is available for Windows, Linux and Mac operating systems. The built-in help file inside PHD2 contains a wealth of information, or you can download the instruction manual here .

My autoguiding graph in PHD2 using the Sky-Watcher EQ6-R Pro telescope mount

PHD2 Guiding Settings for Astrophotography

I have found PHD2 Guiding to be an incredible tool for my backyard deep sky astrophotography. I have been using this software for a long time, starting with the original PHD “1” verion. The latest version of the software (PHD2) has been totally overhauled by a team of passionate developers that aim to make autoguiding even better.

Download the latest version of PHD2 Guiding

The guys over at the Astro Imaging Channel released an informative video featuring one of the team members of PHD who worked on the software.  Andy Galasso quickly reveals just how passionate he is about the project, and how knowledgeable he is with the PHD guiding software.

The video is quite long, but contains a wealth of information about autoguiding with PHD:

The intelligent folks over at PHD can explain the full power of PHD2 guiding better than I can, but I thought I would share what I personally took away from this enlightening presentation.  Before adjusting the settings in PHD2 Guiding, it is important to make sure that your equipment is prepared for imaging.  This includes accurate Polar Alignment and balancing the weight of your payload.

How to use PHD2 Drift Alignment

Here are the top 5 tips I gathered from watching Andy explain exactly how to use PHD2 guiding for best results:

Use the Guiding Assistant

Find this feature under Tools > Guiding Assistant

As Andy puts it, you’ll want to observe an unguided star motion to see what you are up against. This gives you a window into the amplitude of the RA (Right Ascension) periodic error.  Again, explore this tool for a more detailed insight into your particular mount’s characteristics.

The Right Ascension Max Drift rate displayed in the guiding assistant will display a recommended guide exposure length.  Very handy!

Create a New Profile using the Wizard

The built-in equipment profile wizard in PHD2 guiding allows you to tell PHD exactly which hardware you are using.  Here you can set all of the specific details of your gear.  This includes entering in your guide scope focal length and autoguiding camera pixel size.

At this point it will also prompt you to build a dark frame library.  You’ll want to make sure that PHD2 Guiding is making the necessary corrections relevant to your unique setup.

Use Auto Star Select

PHD 2 Guiding has an advanced feature that calculates the best possible star in your field of view to use for guiding.  It will select a star based on algorithms to avoid over saturated or poorly sized stars.  Why not let PHD choose the best possible star, rather than guessing yourself!

In the past, I would try to select a star that was “medium-sized” and near the center of the frame.  This guessing game no longer takes place thanks to the auto star select feature within PHD2 Guiding.

Try using longer guide exposures

In the video, Andy explains that his tests show that using longer guide exposures results in fewer pulse corrections needed. This was a big eye-opener for me, as I had never given much thought to the guide exposure length I would use.  Generally, my guide exposures were about 1 to 1.5 seconds.  The diagram below illustrates how longer guide exposures can provide a smoother graph:

He recommends using longer guide exposures for improved performance. Earlier, I mentioned using the guiding assistant to give you a recommended guide exposure length.  In the example used for Andy’s equipment, that was an exposure of 2.7 seconds.  As a rule of thumb, do not expose so long that the stars begin to over saturate, or PHD will not be able to provide an accurate pulse correction.

Use the graph. Over/Under Correcting

When looking at the graph in PHD, remember that blue is RA , and red is DEC .  If your graph displays a zigzag pattern like the one below, it is a good sign that you are over-correcting.  Toggle the “corrections” check box to get a visual reference for exactly what PHD is doing.

If you are over correcting, the solution is to decrease the aggressiveness and increase your RA minimum motion.  On the other side of the coin, if you are under-correcting, your graph will look like the image below:

For more information about autoguiding with PHD2 Guiding, please visit the Open PHD Guiding Google Group Forum or the Stark Labs Astronomy Software Forum on Yahoo .  These forums offer answers to many of the troubleshooting issues you may experience while using PHD for astrophotography.

Clearly, I am still learning the ins and outs of this software myself.  I hope to improve my knowledge of PHD2 this year to get the most out of this amazing free resource for astrophotographers.

Improved Autoguiding with the iOptron CEM60

In October 2017, I tested out a new astrophotography mount, the iOptron CEM60 .  One of my main goals was to see if this mount could outperform my Sky-Watcher HEQ-5 Pro in terms of autoguiding, and overall tracking performance.

Have a look at the PHD2  graph I was able to achieve while imaging early on in my testing.  The total RMS error was less than 1 second, and noticeably better than anything I had seen using the HEQ-5 Pro. 

However, the fact that I was now pulse guiding via ASCOM to the mount directly may have made a difference as well.  (This can be done on the Sky-Watcher HEQ5 as well)

PHD Guiding with the Sky-Watcher EQ6-R

A new telescope mount presents an opportunity to compare guiding performance. The Sky-Watcher EQ6-R was very impressive in terms of autoguiding performance right out of the gate. Using the default settings with PHD and the generic ST-4 mount connection, I was able to achieve an impressive guiding graph.

In the screenshot below, you’ll notice that the total RMS error is 0.16 (0.63″). This resulted in an incredibly sharp image with round, pinpoint stars in each frame. Autoguiding with a telescope mount like this means that you will never have to discard image exposures due to bad guiding, and elongated stars. 

My PHD guiding graph using the Sky-Watcher EQ6-R mount

Related Posts:

• Using PHD2 Guiding with the Lodestar X2 Guide Camera
• Autoguiding Camera for the ASIair – ZWO ASI290mm Mini
• Astrophotography Resources: Software and Tools