Jump to content


PHD Guiding Basic Use and Troubleshooting

Recommended Posts

Great explanations Lan !!

I do use the handset and not the EQMOD at this stage (and bought the standard Orion Starshoot Autoguider as you mentioned above).

So, (only to make sure I understand the whole thing):

1. If I use the handset on the mount (e.g. SynScan), which is the way I currently work, I should connect the ST4 cable from the cam to the mount (should I still connect

   the USB cable?) and set the PHD to "on Camera",

2. If (in the future) I would start controlling the mount with EQMOD (following your instructions in this regard), then I should connect the USB (do not connect the ST4)

    and select 'ASCOM' from PHD's 'Mount' menu etc.

You have truly simplified the technical process for me here.

Thanks a lot.


Yes you have it right.  You always have to connect the USB cable from the camera to the laptop regardless.

Link to comment
Share on other sites

  • 2 weeks later...

After going through Lan's instructions, I could easily setup and operate the whole system with very good results. Thank you Lan!

The only thing I would mention is that "calibration" MUST be performed after every position change of the scope. That is, if you are done

with your current subs of the DSO and wish to move to another object, a calibration step should be made. if, for any reason, "force calibration" is

disabled in the PHD setup menu, it would lead to misguiding......


Link to comment
Share on other sites

Okay this kind of answers my thread pleading for help :rolleyes:

I will work through this thread to see if I can sort myself out. I did look ro see if info was there before posting a new thread I promise :) although I wasquite late at night.


Sent from my GT-I9505 using Tapatalk 4

Link to comment
Share on other sites

From the code of openphd: 

            // check to see if it seems like the star we just found was the            // same as the orignial star.  We do this by comparing the            // mass            double massRatio;            if (newStar.Mass > m_star.Mass)            {                massRatio = m_star.Mass/newStar.Mass;            }            else            {                massRatio = newStar.Mass/m_star.Mass;            }            massRatio = 1.0 - massRatio;            assert(massRatio >= 0 && massRatio < 1.0);            if (massRatio > m_massChangeThreshold)            {                m_star.SetError(Star::STAR_MASSCHANGE);                pFrame->SetStatusText(wxString::Format(_("Mass: %.0f vs %.0f"), newStar.Mass, m_star.Mass), 1);                Debug.Write(wxString::Format("UpdateGuideState(): star mass ratio=%.1f, thresh=%.1f new=%.1f, old=%.1f\n", massRatio, m_massChangeThreshold, newStar.Mass, m_star.Mass));                throw THROW_INFO("massChangeThreshold error");            }
Link to comment
Share on other sites

What does it mean when while guiding PHD reports and error like this: Mass (some big number) vs (another big number). Also the screen flashes red and beeps.

This is the star mass, which is basically a measure of how bright the star is.  If the brightness changes too much from one exposure to the next, you will get a warning like you are seeing and no guide command will be issued for that exposure,

You need to figure out the cause of the problem if you can.

- It may be that you are guiding on a faint star that is pretty marginal.  Poor seeing, high cloud or dewing on the scope might exacerbate brightness fluctuations in these cases leading to the warnings.  Try going for a brighter guide star if possible and ensure the scope is free of dew and well focused.

- If you have a small aperture finder guider coupled with a not very sensitive guide camera (e.g. webcam) try increasing the exposure length a bit.  Obviously you want to keep the exposure as short as possible, but not if that produces a star that is badly affected by seeing, etc.

- Of course a bigger aperture guide scope or better guide camera would also improve things.

If all else fails, you can increase the tolerance of PHD to star mass changes, but this should only be done once you have exhausted other options as described above (well I'd maybe try the tolerance change before spending money):

- Go in to the 'brain' icon and check the value of the "Star Mass Tolerance" box.  I think the default is 0.3.  If you increase it to 0.4 or 0.5 PHD will tolerate bigger changes in brightness and continue guiding.  From what I have read (never having had to change this parameter myself) going much over 0.5 is not necessarily a good idea.  PHD will continue to guide, but if the star is fluctuating that much it is likely you will have bad guiding anyway.  (It would be a bit like turning off the fire alarm in a burning building; you feel a bit better about things for a while, but not for very long).

- If you set the tolerance to 1 then PHD doesn't bother checking at all and will just try to guide come what may.

Hope this helps.

  • Like 1
Link to comment
Share on other sites

  • 3 weeks later...

There is one issue that I haven't been able to resolve so far. I have problems when guiding and tracking an object that is near the zenith. Everywhere else in the sky guiding works fine (i can manage 20 minutes without star trails) but when I point the scope directly above I get trails after 3 minutes. I have tried both pulse guiding and ST4. Any thoughts?

Link to comment
Share on other sites

  • 3 weeks later...

There is a lot of development on the Open PHD2.

PHD2 Forum https://groups.google.com/forum/?fromgroups#!forum/open-phd-guiding

PHD2 Development Betas http://adgsoftware.com/phd2/

PHD2 Changes https://code.google.com/p/open-phd-guiding/source/list

PHD2 Bug List https://code.google.com/p/open-phd-guiding/issues/list

Take a look, have a play and report issues to make PHD2 better. Some great new features like better visuals, polar align, drift align.......

Link to comment
Share on other sites

  • 7 months later...

G'day, I have a G-Star x , It's not listed in the select camera list, which camera should I select, thanks.

You need a guide camera with a suitable driver for use with PHD.  The new version of PHD (http://openphdguiding.org/) supports the following cameras (taken from the manual):

Camera Selection

The Camera drop-down list shows all the camera types currently supported by PHD2.  With the exception of ASCOM-compatible cameras, the camera drivers are bundled with  PHD2  and will reside on your system after the PHD2installation.  ASCOM-compatible camera drivers are available from the ASCOM web site or from the camera manufacturer, and the drop-down list will show only those ASCOM cameras that are already installed on your system, if any.

The list of supported cameras at the time of writing is shown below - but users should consult web resources to see updates (e.g. Stark Labs)

Supported cameras, December 2013:

  • ASCOM v5/6 compliant cameras (Windows)
  • Atik 16 series, 3xx, 4xx, 4000, 11000 (Windows)
  • CCD-Labs Q-Guider (Windows)
  • DCAM compliant Firewire (OS X)
  • Fishcamp Starfish (Windows and OS X)
  • Meade DSI series: I-III, color and Pro (Windows and OS X)
  • MagZero MZ-5 (Windows)
  • Orion StarShoot DSCI (Windows)
  • Orion Starshoot Autoguider (Windows)
  • Orion Starshoot Planetary Imager and Autoguider (Windows)
  • Opticstar PL-130 / PL-130C (Windows)
  • SAC4-2 (Windows)
  • SBIG (Windows and OS X, but see Help for details)
  • Starlight Xpress SXF / SXVF / Lodestar (Windows and OS X)
  • The Imaging Source (Windows and if Firewire, OS X)
  • Webcams (short and long-exposure - parallel port, serial port or LXUSB, Windows).
Link to comment
Share on other sites

  • 4 months later...
  • 2 months later...
  • 1 month later...

Hello Ian, and thanks for the great tutorial. I have a 150/750 Newtonian with an OAG.Small chip and pixels of my QHY5L-II guider result in being somewhat oversampled . I have 1.8" main and 1.08" guide cam pixel scales. All of the tutorials I have seen seem to be for folks with undersampled rigs and external guide scopes. Would it be possible to add a bit comparing and contrasting settings for external guide scopes with those for OAGs?

Link to comment
Share on other sites

I have only had a small amount of experience with an OAG and not a lot of luck so any advice from me comes with a health warning. What occurs to me is:

- A small pixel scale might lead to a lower SNR on the guide star, but this is likely to be offset to some extent by the bigger aperture of the main scope gathering more light. Nonetheless finding a guide star with the OAG may need you to pick a relatively faint one. So OAGs tend to need longer guide exposures, 7 seconds plus is not uncommon vs. 1 or 2 seconds for a guide scope.

- That in turn means you need a mount that tracks better between guide corrections. So polar alignment becomes important, as does a lower periodic error. Using PEC can make a big difference but ultimately you will need a mount with good mechanicals, especially at longer focal lengths.

- As for PHD settings, calibration should take care of most issues automatically provided you adjust the calibration step size. PHD 2 has a calculator to help work this out. You might want to increase the Min Motion setting if you are oversampling the seeing to avoid chasing it, but I suspect the longer exposures will average that away.

- The main challenge is the gap between guiding commands due to the long exposure. I think you would want to use Resist Switch in declination, or guide in one direction only if you have slight drift, as backlash and constant changes of direction will be harder to control with long gaps. In RA I'd be inclined to use at least 100% of the correction for RA Aggressiveness and reduce the amount of hysteresis so that you are relying more on the current error than error from many seconds ago. From there tweak based on the guide graph, again PHD 2 has more options and tools for this but I am not sure I entirely trust it yet.

Others may have some better ideas based on more experience.

Edited by IanL
Link to comment
Share on other sites

A great article on guiding thank you I have learnt a lot. Please may I ask though, what guide speed should I use? On my neq6 mount there are several options: 1x, .75x, .5x, .25x and .125x. How do I know which to use and should I set it on the synscan handset? I am using the st4 port.

Link to comment
Share on other sites

The major long waves on my guide chart above were 100% caused by a mechanical problem that I caused. The guide motors are interchangeable, so stupid me I assumed the worms were as well. Wrong!. Tech support caught is and all that is gone now. Still a rough looking graph , but seeing has been so hazy that by 10 pm the only lights visible in the sky are Jupiter and Sirius. Best SNR I can manage right now is 4-5, so I don't think I'll have useful guiding or imaging until I have decent seeing. When a hole in the haze passes by it seems to guide under 2"rms, but only briefly before seeing closes out again. Obviously no fine tuning possible.

A great article on guiding thank you I have learnt a lot. Please may I ask though, what guide speed should I use? On my neq6 mount there are several options: 1x, .75x, .5x, .25x and .125x. How do I know which to use and should I set it on the synscan handset? I am using the st4 port.

With my mount, 1x is the only choice that gives a useful result. I think the start with .5x and work your way around to your best result strategy is wise for other mounts, however. I'm finding if I adjust the exposure length to the longest which will hold the star, then let it settle. I then make cautious adjustments from there, waiting a few minutes and then evaluating the graph, that this approach works pretty well. I believe only one correction per exposure can be made. If the speed is too low, the trace may run away and back because of under correction, if too fast it may be choppy from excess corrections. I'm just learning.

  • Like 1
Link to comment
Share on other sites

Hi all

Does anyone have a problem with an image in PhD that is so grainy that you can't see anything, let alone a star? I have tested the setup in the day time to ensure it all functions but at night I can't see anything, not even Jupiter!

Granted, I haven't had much time to play with it as it's been cloudy for the last two weeks (that'll be my fault for buying a new mount and scope!) but I don't seem to have any joy playing with the gain and exposure etc.

I use a Logitech quickcam pro 4000 and my guide scope is an 800mm ds2090 (it's my old scope and only choice atm!) has anyone had any experience with this web cam, or similar issues?

Unfortunately I don't have a screen shot but it looks like the image you used to get on old TVs when they had no signal and if I adjust the exposure, or brightness it just goes completely black with no stars!

Thanks in advance for any tips!


Link to comment
Share on other sites

The thing that stands out to me from your thread is the FL of your guide scope. 800mm is longer than most imaging scopes. Mine is 328mm and that is consider long for guiding. I'm not familiar with the camera type you describe. Are you using PHD 1 or 2 as 2 automatically steps the gain up and down until a suitable star is selected.

Link to comment
Share on other sites

I know it's a rather long FL compared to most guide scopes, I was hoping I would get away with it to save me spending any more money as I've just splashed out nearly a grand on my avx mount and sw ed80 apo and i'm desperate to get longer than 60 second exposures!

I have both PhD and PhD2 but I was trying phd2 as it asked for the basic details of the guide scope and cam setup and automatically set some rough default values to suit.

The pixel scale is about 1.44 ish and my imaging scope is about 1.9. Could the pixel scale be too small for guiding perhaps? I would've thought I'd be able to see a star (or planet) at least, regardless of whether it guided properly or not!

Perhaps one day soon the clouds will kindly move on so I can have a proper crack at it!


Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.