The Flat Panel / Cover is accessible from Gear tab.
Click on the Flat Panel / Cover button to open/close Flat Panel / Cover controlling panel from where is possible to control ASCOM compatible flat panel and/or cover devices. Note that if your flat panel doesn't have ASCOM driver you can check the Extra Devices Panel where some models can be controlled via direct serial communication.
When there is active connection there will be asterisk in the Flat Panel / Cover button name in Gear Tab. Note that closing the panel window does not disconnect the device. You can open and close the panel as many times as you need in order to keep the interface clean without worrying about the connection to the device.
The panels and the cameras should work in tandem in order to get best results. In one hand the panel need some time to reach the exact brightness. In other hand the most of the cameras has electronic (rarely mechanical) shutter, so if you start exposure when the panel is turned On is possible to gets slightly different amount of light in top and bottom areas of the sensor as it takes time to read the lower pixels which are still exposed to the panel light.
The optimal workflow is to start the exposure, turn the panel On for some time, after that to turn it Off and after that to end the exposure. So far so good, but as it was mentioned the panel needs some time to turn On/Off. Let name it this delay as X. When we want to make a flat frame with 5s duration, we have to make it for 5s + 2*X in order to be sure that every sensor pixel will get same amount of light. Because determining the delay could be tricky APT gives way to calculate it depending on the statuses provided by the ASCOM driver. Use the Calc button several times to see how the milliseconds vary. If the values are constant you can leave the setting as it is. If they vary or you want to be on the safe side, you can increase the max value you got with small value like 5-10%.
The brightness levels per filter can be defined in Filter Wheel settings tab. If you are using Color/OSC - One Shot Camera, just enter OSC on the first line and the needed brightness. Keep in mind that you can use the Manual Filter Wheel support for manual wheels and filter drawers.
Here is how Flat Panel / Cover looks like:
Connect / Disconnect
When you connect a Flat Panel / Cover for the first time you will be asked to select the connection parameters by the standard ASCOM dialog. APT will remember your selection and when you click again on the “Connect” button it will use the previous settings automatically. If you want to change the connection parameters, use “Shift+Click” on the Connect button. Use Ctrl+Click to forget the selected connection parameters.
Opens the settings dialog of the ASCOM driver. If this action is not supported by the driver, use Shift+Click on Connect button and then click Properties in the driver selector dialog box.
When a Flats Imaging Plans is executed in DSLR or CCD/CMOS or CCD Flats Aid is used and flat panel is connected, it will be automatically controlled. When panel is automatically connected the brightness levels per filter are defined in Filter Wheel settings tab. If you are using Color/OSC - One Shot Camera, just enter OSC on the first line and the brightness. Keep in mind that you can use the Manual Filter Wheel support for manual wheels and filter drawers.
Defines how many milliseconds are needed to the panel to reach from 0 to stable brightness with the desired percent. This value will be used to calculate the exact exposure duration. See above the notes on how the panels and the cameras work together.
The Flat Panel / Cover is accessible from 
