Comet Tracking
One way to image a comet is to have PHD2 use the comet as the guide "star", but this approach may not always work. For example, the head of the comet may not present a star-like center suitable for guiding. Or, when using an off-axis guider, the comet may not even be visible in the guide camera.
PHD2 provides a Comet Tracking tool for use when guiding on the comet itself is not feasible. The idea is to guide on an ordinary star, but to gradually shift the lock position to match the comet's motion, or tracking rate.
There are a three different ways to provide the comet tracking rate to PHD2.
Some planetarium applications, like Cartes du Ciel, can send the rate directly to PHD2;
You can enter the tracking rate manually, or,
You can train the rate in PHD2 by following the comet for a period of time in the imaging camera.
To enter the rate manually, you would select "Arcsec/hr" for units and "RA/Dec" for axes, then enter the rates from the comet's ephemeris.
Comet rate training works like this:
First, center the comet in your imaging camera. If your imaging application has some kind of reticle display, you should use that to note the precise position of the comet on the imaging sensor. Once this is ready, select a guide star in PHD2 and start guiding. Next click "Start" in the Comet Tracking tool to begin training.
Take a continuous series of short exposures in your imaging camera using your imaging application's Frame and Focus feature. Over time, the comet will drift away from the starting location. Use PHD2's "Adjust Lock Position" controls to move the comet back to the starting location. You may have to experiment a bit to determine which way the comet moves on the imaging camera sensor in response to the Up/Down/Left/Right controls in PHD2. You may find it useful to enable the "Always on top" button in the Adjust Lock Position window so the controls stay visible on top of your imaging application.
PHD2 will quickly learn the comet tracking rate as you re-center the comet. Once you are satisfied that PHD2 is tracking the comet, you can click Stop to end the training. PHD2 will continue shifting the lock position to track the comet until you disable comet tracking by toggling the Enable button.
You can practice the comet training technique using the built-in camera simulator. Check the "Comet" option in the Cam Dialog, and the simulator will display a comet. Use a bookmark to mark the comet's starting location, and use the Adjust Lock Position controls to move the comet back to the bookmark location.
Managing Equipment Profiles
Equipment profiles were introduced in the section on Basic Use where they are used as part of the 'Connect Equipment' dialog. If you want to manage multiple profiles, you will probably want to use the 'Manage Profiles' button in the 'Connect Equipment' dialog. Using the menu items there, you can create a new profile or edit/rename/delete an existing one. Each profile holds all the settings that were active at the time the profile was last used. If you create a new profile, you can import these settings from either the PHD2 generic defaults or from an existing profile. You can also use the 'Wizard' option to have PHD2 establish settings that are specific to your equipment configuration. To edit the settings in an existing profile, you first select it in the equipment profile drop-down list, then click on 'Settings' under the 'Manage Profiles' pull-down. This will take you to the 'Brain' dialog, where you can make whatever changes you want. Remember than profiles are automatically updated anytime settings are changed during a PHD2 session. Finally, you can import and export profiles for purposes of debugging, backup, or even exchange with other PHD2 users.
Advanced Settings for the Simulators
The device simulators were introduced in the Basic Use section as useful tools for you to experiment with PHD2 and become famliar with its features. Remember that you must choose 'Simulator' as the camera type and 'On-camera' as the mount type in order to get the benefits of simulation. As you become more interested in the details of the simulation, you can use the 'Cam Dialog' button on the main display to adjust the simulation parameters:
You can adjust simulated mount behaviors for declination backlash, drift due to polar mis-alignment, and periodic error. You can also adjust the 'seeing' level, which will create fairly realistic guide star deflections that look like seeing effects. If you adjust these parameters one-by-one, you'll see how they affect star deflections and how the different guide algorithms react to those movements. Of course, you're dealing with a "nearly perfect" mount in these scenarios (except for backlash), so the simulation can't be entirely realistic.