The PHD2 main window is designed for ease of use and clarity.
Its intent is to support a quick and natural sequence of
interactions to start and control guiding. The basic steps
for doing this are as follows:
- Connect to your guide camera and mount
- Start a sequence of guide exposures to see what stars are
available in the field of view
- Let PHD2 auto-select a suitable star and calibrate the guider
- Continue guiding on the target star while using various
display tools to see how things are going
- Stop and resume guiding as necessary
The majority of the screen is taken up by the display of the star
field from your guide camera. The display is automatically
adjusted for size, brightness, and contrast so you can view
the available stars. However, these adjustments are done
for display purposes. Internally, PHD2
operates on the raw,
un-adjusted data in order to maximize guiding accuracy. This
display can also used to manually select a guide star by clicking
on it although it's better to use the 'Auto-select star' feature..
You can adjust the slider control to see
even the faintest stars in the field.
Basic controlNear the bottom of the screen are the main
controls. PHD2 is largely controlled by these buttons and
sliders, with additional pull-down menus at the top of the window for
more detailed functions. Moving from left to right in the
window, the primary buttons are as follows:
- The USB connector icon - used to connect to your camera and mount devices
- The Loop icon - used to start a sequence of repeated exposures with the
guide camera ("looping"), with each resultant image (guide frame) being
displayed in the main window. If guiding is subsequently started,
clicking on the 'loop' icon again will pause guiding while continuing
to take guide exposures.
Auto-Select Star icon - used to trigger an automatic selection of the
best guide star candidate in the field of view. This selection is
done quantitatively, taking many things into account - star saturation,
minimum star size, signal-to-noise ratio, proximity to other stars,
proximity to the edge of the field, etc. The technique will
nearly always make a better choice than you can manually even though
the selected star may appear quite faint.
- The PHD2/Guide icon - used to start calibration, if needed, and then to start guiding on the selected star.
- The Stop icon - used to stop both guiding and looping
To the right of the stop icon is a pull-down list of exposure
durations (0.01s - 15s). You use this control to quickly set the guide
camera's exposure duration. If your camera does not support an
exposure duration, PHD2 will do its best to emulate that duration.
For example, if you use a short-exposure webcam, your maximum
true exposure duration might be only 1/30th of a second. If you
select one second as the desired exposure time, PHD2 will automatically
acquire images for one second and stack them on the fly to create a
composite image for guiding.
The next control to the right is a slider for adjusting screen
stretch and contrast, essentially a "gamma" adjustment. PHD2
automatically adjusts the display accounting for the darkest and
brightest pixels in the image, and the slider is used to fine-tune the
display to better see the stars in the field of view.
This may be useful, for example, if you are trying to focus the
guide camera for the first time and need to see the large, out-of-focus
star image. Moving the gamma slider only makes the display brighter or
dimmer for your viewing. PHD2
always uses the raw pixels from the camera for guiding, and moving the
gamma slider has no effect on guiding. A display of "completely
white" or "completely black" is usually an indication that no stars are
available in the field of view. The automatic gamma-stretching of
the image is a very common source of confusion for users because they
don't adjust the gamma slider properly to see faint stars on the
display. The stars that PHD2 auto-selects may appear to be overly
faint and inferior to bright stars you see in the display. These
results are illusory because PHD2 can generally do a better job of
selecting a guide star than you can accomplish by eye. As a rule
of thumb, if you've chosen a star whose name is known to you, it is
almost certainly too bright to be a good choice as a guide star.
Next to the gamma slider is the "brain button." This button brings up an Advanced Dialog for making detailed adjustments to PHD2's
guiding operations. An important
design goal of the program is to minimize your need to change these
parameters, but "the brain" is nothing to be feared - there are
adjustments available there that can improve your guiding
results and make your life easier. Over a period of time, you
should take a look at this
dialog and learn what it can do for you.
The rightmost control in this row is a "camera properties" button.
Depending on the particular camera, this button may be enabled
to provide access to a configuration dialog unique to the camera.
However, common camera properties such as gain and binning will
normally be set in the 'Camera' tab of the PHD2 Advanced Dialog.
If the button is disabled, any available properties can be set in
the PHD2 Advanced Dialog. With the newer class of guide cameras,
this button is often disabled because it adds no capabilities beyond
what is available in the PHD2 Advanced Dialog.
MenusThe pull-down menus above the main guider display are used to access a variety of functions. These are described in the Darks, Tools and Utilities, and Visualization sections of this help document.
The status bar at the
bottom of the main window is
used to display messages and status information that will help you keep
track of guiding operations.
the center of the status bar are fields showing the current state of
the guide star. If the SNR value drops below 10, its value will
be shown in yellow as a warning that you may encounter some 'lost-star'
events. If the guide star is saturated, the field to the left of
SNR will show 'Saturated' in a red typeface.
the right of the
star status fields are two text fields showing the latest RA and Dec
guide commands. These show the size of the guide pulse, the guide
star displacement size in pixels, and an arrow showing the
The arrows follow the usual compass conventions: Dec up/down
corresponds to north/south, RA left/right corresponds to west/east.
All of this information is captured in the log files and
displayed in the various graphical tools, and those are what you should
use for visualizing your guide performance. But these status
fields may give you a quick visual clue when something is behaving
The rightmost panels in the status
bar show icons that give you visual clues about the current state of
PHD2:. These icons are color-coded to give you a dashboard view of current status and have the following meanings:
- red means neither a dark library nor a bad-pixel map is being used,
green means one or the other is in-use. If you're
using a bad-pixel map, the text will say 'BPM' rather than 'Dark'
- shows the state of calibration. Red means the mount is
currently uncalibrated, while yellow means there is a calibration but it
isn't being adjusted automatically to account for scope pointing
position. This will happen when you aren't using either an ASCOM
or 'aux' mount connection in PHD2. If the icon is yellow, you
will generally need to recalibrate when you move the scope to different
"The Ball" - shows whether all the
equipment in your profile has been successfully connected. If the
ball is yellow, some components are not connected, while green means
everything is connected.
If you hover the mouse cursor over any of these status icons, you'll see details about the current state.