Using PHD2 GuidingThere are five basic steps to start guiding.
- Press the USB-icon button and connect to your guide camera and mount.
- Pick an exposure duration from the drop-down list.
- Hit the loop button and look at the available stars, adjusting focus if necessary. Move the mount or adjust the exposure duration as needed to find a suitable guide star.
- Click on a non-saturated star that's not very near an edge for use as the guide star.
- Press the PHD2 Guide button.
PHD2 must first connect to your hardware: the guide camera, the mount, and, optionally, an 'aux' mount, an adaptive optics (AO) device, or a rotator. When you click on the USB icon, you'll see a dialog that looks like this:
PHD2. In all cases, the OS-level drivers for the camera must be installed correctly in order for PHD2 to connect to the device. If the camera uses an ASCOM interface, you'll also need to install the corresponding ASCOM driver for the camera. If you don't see your ASCOM-compatible camera shown in the drop-down list, you probably don't have the ASCOM driver installed. Neither the ASCOM nor OS-level drivers are included with PHD2, so they must be located, downloaded, and installed separately. For non-ASCOM cameras, the PHD2 distribution does include the additional application libraries needed by PHD2 to use the camera..
It is not practical to provide an exhaustive list of cameras that are supported by PHD2. In many cases, camera vendors extend their product lines by updating their lower-level drivers without having to change the application libraries used by PHD2. In those cases, we aren't aware of the changes unless a user reports problems. The list shown below should be interpeted as follows:
1. If the camera vendor is completely absent, it is unlikely that the camera is supported, or it may only be supported using a web-cam interface
2. If the camera model is shown in the list, it is supported unless there are unresolved problems with the vendor's drivers
3. If the specific camera model is absent but earlier models are shown, it is likely the camera is supported
4. If the camera uses an ASCOM interface, it is supported
Since the PHD2 download is free, the simplest course of action is to install it and see if your camera is shown in the PHD2 drop-down list. Alternatively, you can check for camera support info in the Wiki on the PHD2 Google forum: https://github.com/OpenPHDGuiding/phd2/wiki/CameraSupport
Finally, you can always post a message on the open-phd-guiding forum asking if anyone has experience with the camera.
Baseline list of supported cameras:
- ASCOM v5/6 compliant cameras
- Atik 16 series, color or monochrome
- Atik Gen 3 color or monochrome
- CCD-Labs Q-Guider
- Fishcamp Starfish
- iNova PLC-M
- MagZero MZ-5
- Meade DSI series: I-III, color and monochrome
- Orion StarShoot DSCI
- Orion Starshoot Autoguider
- Orion Starshoot Planetary Imager and Autoguider
- QHY 5-II
- QHY 5L-II
- SBIG rotator
- Starlight Xpress SXF / SXVF / Lodestar
- Webcams (LXUSB, parallel, serial, OpenCV, WDM)
- ZWO ASI
- Fishcamp Starfish
- Meade DSI series: I-III, color and monochrome
- Orion Starshoot Autoguider
- Starlight XPress SXV
- The Imaging Source (DCAM Firewire)
- ZWO ASI
ASCOM Camera PropertiesIf you choose an ASCOM camera, you'll also be able to access the ASCOM setup dialog for that camera by clicking on the properties button immediately to the left of the 'Connect' button:
Depending on the camera, this may provide access to properties that are not controlled by PHD2.
Multiple Cameras of the Same TypeIf your computer is connected to multiple cameras from the same manufacturer, you'll usually need to specify which camera should be used by PHD2. You can do that by clicking on the 'fork' button to the right of the camera drop-down list:
Clicking this button will show a list of the available cameras and you can choose the one you want. PHD2 will remember the choice and save it as part of your equipment profile, so you should only need to do this once.
- Use an ASCOM-compatible telescope driver that sends guide commands to the mount over a serial cable (or more commonly, a USB/Serial connection)
- Use the ST-4 compatible guide port interface on the mount with a specialized cable and an intermdiate device like a camera or a Shoestring box
The "Guide-port" interfaces use a specialized, hardware-level control port available on most mounts. To use this type of interface, there must be another device in the link between PHD2 and the mount:
- Any of the guide cameras which have an ST-4 compatible "on-camera" guider interface. Use the 'on camera' mount choice for these setups.
- Any of the Shoestring GP-xxx devices
- A supported AO device with a guide port interface
For Windows users, the "aux" mount can use any of the ASCOM-compatible mount drivers, while Linux users can take advantage of INDI drivers. The "aux" mount choice will be used only if the primary mount interface cannot return pointing information - it will otherwise be ignored. Note: some mounts (e.g. Celestron and iOptron) have a separate hardware port also labeled 'Aux' - DO NOT USE THIS for guiding - it is completely unrelated to the 'Aux' connection in PHD2.
The last entry in the list of 'Aux mount' connections is labeled "Ask for coordinates." This can provide a rudimentary aux-mount facility if you can't use an ASCOM or INDI connection to your mount. If you need to pursue this option, you can read about the details in the Tools section.
- A drastic reduction in the number of re-calibrations you'll need to perform. Changing targets will not require another calibration because PHD2 can know where the scope is pointing and automatically make adjustments to the guider calibration. Most users get a good calibration and then re-use it until they make hardware changes of some kind.
- Automatic adjustment for meridian flips - no need to remember to manually flip the calibration data.
- Automatic adjustment of RA calibration to handle targets in different parts of the sky (declination compensation)
- Elimination of the ST-4 guide cable as a point of failure - this is a surprisingly common problem because the cables can be damaged or confused with similar-looking cables (e.g. telephone cables)
- Elimination of a moving cable that can snag, drag, or bind as the scope is moved around.
- Improved ability for PHD2 to sanity-check calibration results and warn of possible problems before you waste hours of imaging time.
- Better diagnostic and trouble-shooting information, which is particularly helpful if you need to ask for assistance
- Availability of scope-slewing options during drift alignment which can further speed the process of polar alignment
If you don't have these devices, just leave the selections at 'None.' If these devices are connected, you'll see additional tabs in the 'Advanced Settings' dialog that provide access to various device-related properties. PHD2 does not control a rotator, but it will read the current angle setting from the rotator and adjust the guiding calibration if needed.
PHD2 devices - camera, mount, AO, rotator - include built-in simulators. You can use these simulators to explore how PHD2 works and to decide how you want to use the program. There's no reason to waste valuable dark-sky time learning to use PHD2! Virtually all of PHD2's features, including full calibration and all the graphical display options, will work properly when device simulators are used. You will even see fairly realistic guiding performance to give you some idea of what to expect in the field. To get started using the simulators, choose 'Simulator' for the camera type and 'On-camera' for the Mount type.
That said, the simulators are not useful for trouble-shooting any problems you encounter with your real mount. Both the camera and the mount must be real devices in order to diagnose problems or otherwise get your gear calibrated and working. In that sense, what you see when using the simulators is realistic but "fake" behavior. The simulators can be useful in some cases for reproducing PHD2 application problems, but not for anything having to do with your actual guiding equipment.
PHD2, default or otherwise, are automatically stored as part of an equipment profile. If you have only one guiding setup - you use the same camera and guide scope combination each time - you will only need one profile; and you can just use the default profile. But you may have multiple equipment configurations - for example, an off-axis-guiding arrangement for a long focal length scope and a separate guide scope/camera configuration for a shorter focal length imaging scope. The PHD2 guide settings for those configurations are likely to be different, so you would want to use separate equipment profiles The controls at the top of the 'Connect Equipment' dialog let you choose the profile you want to use and to create/edit/remove profiles as you see fit. When you select a profile and connect to its associated equipment, all of the settings last used with that profile are automatically reloaded. Once you've established the profiles you need - perhaps only the default one - you can simply click on the 'Connect All' button and you're ready to move ahead. If you already have a suitable default equipment profile and you simply want to connect to the equipment just as before, you can do a <shift>-click on the main screen 'USB' button and PHD2 will automatically re-connect to your hardware.
The wizard asks a number of questions that are important for getting your profile built correctly. The explanatory text in each pane of the wizard should make clear what is being asked and what needs to be done. But here are some additional tips to help you through the process:
2. Camera connection pane: guide scope focal length. This seems to be a common place for mistakes, so it's worth being careful and getting it right. The correct value is not the aperture of the guide scope, it is the focal length. So, for example, if you're guiding with a 50mm finder scope, the focal length willl not be 50mm - it will probably be something closer to 150-175mm. A 60-80mm refractor guide scope will probably have a focal length in the range of 240-500mm, not 60-80mm. Similarly, if you're guidng with an OAG on your main imaging scope, the focal length will be that of the main scope. In some cases, you may be using a small threaded focal reducer on the guide camera, so that must also be taken into account. Like the pixel-size entry, the focal length doesn't demand a great deal of precision, but you should get as close as you can. Otherwise, the performance numbers may not reflect your actual results.
3. Mount connection pane: mount guide speed. This is another area that seems to cause confusion. The guide speed is a parameter set in the mount or in the mount driver, it's not something controlled by PHD2. PHD2 never sets the mount guide speed, it only reads it. It is usually expressed as a multiple of the sidereal rate and is typically in the range of 0.5x - 1x sidereal. Despite what you may read elsewhere, it's generally best to use guide speeds in this range rather than much lower speeds. Higher guide speeds can help to clear backlash more quickly and may help to overcome stiction problems. If you have the mount physically connected and are using an ASCOM (or Indi) interface, you can click on the 'Detect' button and PHD2 will attempt to read the current guide speed from the mount. If this fails for some reason, you'll need to enter the guide speed manually. PHD2 uses this value to automatically set the calibration step-size and to aid in checking calibration results; but the guide speed information is not important for the actual guiding. If you're using different guide speeds on the RA and Dec axes, enter the larger value. If you really can't determine what the guide speed settings are in the mount, leave the setting at the default value of 0.5.
In the last pane of the wizard dialog, you're given the option to build a dark library for the profile, You should always do this unless you already have a compatible dark library that you're going to import from a different profile. If you are changing cameras and want to keep the dark libraries and bad-pixel maps associated with the old camera, you should create a separate profile for the new camera. When a camera selection is changed in an existing profile, the previously built dark library and bad-pixel map data will no longer be usable. That also applies to using the same camera with different binning values. Setups using different binning factors should be kept in separate profiles because the dark library and bad-pixel maps depend on the binning factor.
PHD2 will find the star nearest to the cursor. After you do this, a green box will appear to frame the star. If you pick a star that is too bright, a message box will tell you the star is saturated, and you should either use a different star or decrease the exposure duration. The choice of exposure time will depend entirely on your equipment, sky conditions, and the available stars. The exposure time you choose has several implications:
- It affects the signal strength (brightness) of the selected star - a brighter star will stand out better from the background and will generally produce better guiding results so long as it is not saturated.
- It also determines the frequency with which guide commands are sent to the mount - guide commands cannot be sent any more frequently than once for each exposure cycle. Some mounts benefit from frequent small guiding adjustments while others do not - you may need to experiment to understand what works best for your situation.
- It has a strong effect on the sensitivity of the guide algorithms to seeing conditions. As the exposure time is increased up through 4-6 seconds, the effects of seeing are smoothed out. The camera is essentially averaging out the larger, high-frequency seeing movements, so the guide algorithms have less difficulty distinguishing "seeing jitter" from actual guide star displacements that need to be corrected.
There is also an Auto exposure time selection available. When exposure is set to Auto, PHD2 will attempt to adjust the exposure to keep the selected guide star at a constant signal-to-noise ratio (SNR) value. This is a specialized measurement used by PHD2 to determine how well the star can be distinguished from the background - it is similar but not identical to the signal-to-noise ratio used in photometry. The Auto setting is primarily intended for AO users who want to minimize exposure time without losing the guide star. The settings to control Auto-exposure are on the Camera Tab of the Advanced Dialog. Non-AO users should probably not use the "Auto' exposure setting because it complicates interpretation of the guiding results.
Conventional MountsTwo things need to be measured by PHD2 as part of guider calibration:
- The angle of the camera relative to the telescope axes
- The length of the guide pulse needed to move the telescope by a specific amount
Although PHD2 moves the guide star in all four directions, only the west and north movements are actually used to compute the guide rates and camera angle. The east and south moves are used only to restore the star roughly to its starting position. Before the north moves are begun, you will see a sequence of pulses that are intended to clear backlash. PHD2 takes a fairly aggressive approach to clearing this backlash, watching for a clear pattern of movement in a single direction with no reversals. Even so, these pulses may still not clear all the declination backlash in your mount, particularly if you are significantly affected by seeing conditions. In that case, the computed declination rate may be too low, a situation that is discussed further in the Tools and Utilities section. You may also see that the south pulses leave the guide star well-short of its starting position - this is another visual clue that you have significant declination backlash in your mount. If you see evidence of sizable backlash, you can run the Guiding Assistant tool and measure it directly.
In most cases, calibration will complete automatically without any user involvement. If you get frequent failures during calibration, you should consult the trouble-shooting section.
If you're using an ASCOM (or Indi) connection for either the 'mount' or 'aux-mount', a good calibration can be re-used for a long time, and that is the preferred way to operate. These connection options allow PHD2 to know where the telescope is pointing, so a calibration done at one point in the sky will be automatically adjusted as you slew to different targets. The old method of having to re-calibrate whenever you slewed the scope or switched the side-of-pier is a thing of the past so long as PHD2 has pointing information. With this type of set-up, you would only re-calibrate if you rotate the position of the guide camera by more than about 5 degrees or make other major changes to the hardware configuration. In general, the best practice is to get a good calibration within about +/- 20 degrees of the celestrial equator and high enough in the sky to avoid major seeing (turbulence) problems. Since PHD2 has pointing information for this type of configuration, the 'Auto restore calibration' option in the Guiding tab of the Advanced Dialog will be checked automatically. From this point forward, you can simply connect to your gear, choose a guide star, then begin guiding immediately. Finally, if you're using an instrument rotator as part of your equipment profile, PHD2 can use the 'Rotator' connection to adjust the calibration data based on the angular position of the guide camera - one less reason for re-doing a calibration.
You can always review the results of your last calibration by using the 'Tools' menu and clicking on 'Review Calibration Data' That will open a dialog that shows a graphical representation of the mount's movements along with the values that were computed for guiding your mount. This window is described elsewhere in the Calibration Details section of the help file. As a quick quality check, you can open this window and confirm that 1) the RA and Dec lines are roughly perpendicular and 2) the plotted points are roughly linear with no significant curves, bends, clumping of points, or reversals in direction. If you do see these kinds of odd patterns in the graph, you should probably re-do the calibration. Even with high-end mounts, calibrations can occasionally go awry because of environmental conditions, especially wind and bad seeing.
After a calibration is completed, PHD2 will "sanity check" the results to be sure the calculations at least look reasonable. If they don't, you will see an 'alert' message at the top of the main window that describes the calibration result that looks questionable. You can choose to ignore the alert or click on 'Details' to get more information. It is generally advisable to pay attention to these alerts because there is no point in trying to guide using a significantly bad calibration.
PHD2 will continue guiding until you click on the 'Stop' icon. To resume guiding, simply start looping exposures again, select your star, and click on the 'Guide' button. You will not need to repeat the calibration in order to resume guiding. In some cases, PHD2 may lose the guide star and you'll be alerted by an audible beep and flashing orange crosshairs. There are several reasons this might occur:
- Something may be obscuring the star - clouds, the observatory roof, a tree, etc.
- The star may have abruptly moved out of the tracking rectangle because something shifted in the mount/camera/cabling infrastructure - cable snags can cause this
- The star may have "faded" for some other reason, perhaps because it is overly faint
If you are using a German equatorial mount (GEM), you will usually have to do a "meridian flip" around the time your image target crosses the meridian. This means you will move the telescope around to the opposite side of the pier and then resume imaging. Doing this invalidates the original calibration, typically because the declination directions are now reversed. If you are using an ASCOM (or 'aux' ) mount interface, your calibration will be adjusted automatically and you can simply resume guiding (assuming you haven't also rotated the camera or focuser). If you aren't using an interface that returns pointing position, you will need to take action to adjust the guider calibration. You can, of course, simply do another calibration on the current side of the pier, a process that will typically take only a couple of minutes. Or, you can use the pull-down menu item under 'Tools/Modify Calibration' to "flip calibration data" and then resume guiding immediately. Note: 'flip calibration data' will have no effect if PHD2 is using an ASCOM or 'aux-mount' connection.
In some cases, you may want to force a re-calibration. For example, you may have rotated the guide camera as part of resolving a cable problem. You can do this by clicking on the 'Brain button', moving to the 'Guiding' tab, and clicking the 'Clear mount calibration' checkbox. Or, you can simply do a <shift>click on the 'Guide' button on the main screen and PHD2 will start a calibration run.
Once you have started guiding, you will almost certainly want to know how things are going. You can of course watch the star in the guide camera display but in many cases you won't be able to see all the small adjustments that are taking place. But PHD2 provides many tools for measuring and displaying your performance, as described in the Visualization section. Several of the guiding algorithms have limit settings for the maximum guide correction that can be issued with a single command. If these values are smaller than what is needed to correct the mount's position, you will see an alert dialog at the top of the main window advising you of the situation. If this is a recurring problem, you may want to increase the values for these settings or otherwise solve the underlying problem.