Set your camera to capture at 30Hz if it has a frame format that supports 30Hz:

Select an attached power meter or use the manual calibration tool if power calibration is required. If calibration is required counts will turn to an actual power reading for the total frame power or energy:

You said you need an average so I will assume "Total" is the item you are averaging. It could be any results just enable the one(s) you need:

You need to average 100 shots at 30Hz each hour so you will need to use the Burst Capture feature. The controls below (as currently set) will capture 100 frames every hour in results priority mode (what you need for this requirement).

Provide a log file name here:

Set frame averaging to 100 because you want to average the frames collected. This will produce results that are an average of 100 samples.

Set logging to continuous as you will stop it manually after 30 days.

You could also do the math (Days x Logs Per Day = Total logs or 30x24=720) and figure out how many samples a 30 day log would produce at this rate and place this number in the box below in place of the 1 you see now. Then click on the "Folder/Play-Button" icon to the right of the spin buttons to enable "Stop after X Logs"

When you are ready to start logging, make sure the data source is running and click on the top middle icon you see here, which is the results logging button (has the 1.2 in the icon):

When you are running and click the "Log Results" button the logging to disk will begin.
2D and 3D images (Pro release to introduce image logging) can also be logged by enabling the required image file types here:

Use Excel to import the data from the log file with comma delimiting and you will see the following type of log: This log of total frame counts was made using burst capture of 100 frames every 5 seconds.
Tip: When you setup a log in this way you will only see the frames that are logged appear in the BeamGage beam displays. If you are logging one sample an hour you will not see a lot of activity in the beam display windows. Not to worry, you have the power of Multi-Clienting at your finger tips so you can minimize this instance of BeamGage and let it go on logging in the background (maximize it again when you want to see the last frames logged). Now, launch a new instance of BeamGage and connect to the same camera. Because the camera is set at 30Hz you will see a 30Hz video feed in the second instance of BeamGage. This will allow you to monitor in real-time while you are logging in slow-time.
Behold, the power of subscription rate when combined with logging and multi-clienting.
