A short story about automatic exposure with RPiHQ

[AndreasLMeg]

A short story about automatic exposure with RPiHQ (translated by google):

I started with allsky six months ago and the first really annoying thing was the transition between day and night.
Naive as I am, I immediately tried to find a solution. (Step 1: calculate the mean value of the image and try to keep the exposure time at 0.5)
Relatively quickly, however, this brought headaches and sleep deprivation from constant observation of the pictures and logging and the realization that every adjustment also worsened

That was the reason to take a closer look at the keogram. Was not usable for me either, so there were various extensions (Step 2: expand, channelinfo)

Now I was able to observe the mean value over the night and determine anomalies or potential for improvement:

1. The main problem are the transitions (day / night), the effects of clouds and stray light (cars, moon, ...) The standard values ​​(exposure time, gain) for a clear night are fixed for most users
2. The goal was an appealing video (without overexposure), high coverage (all falling stars) and no constant adjustments because of the moon (I'm very lazy there)

At first I had jumped on the exposure time. I quickly recognized the problem that this was not sufficient for the sunrise / sunset (Step 3: gain regulation)
An attempt was now made to start with minimal gain (1 for day, but only applies to RPiHQ) and to increase the exposure time as desired (60s, and one exposure every 60s). Then the reinforcement is pulled up to the desired one (1,2, ... 15)
keogram feedback: doesn't look too bad, but there were massive jumps at gain 1,2 and 3! -> (Step 4) Research: Relationship exposure time, gain, effective exposure

With this realization (my secret) the results got much better (fewer jumps)
Keogram feedback: Regulating restless or always too late -> (Step 5) Prediction (also my secret) of the next exposure time based on the past

Keogram feedback: Sufficient for me, but still optimizable (I have other things to do besides Allsky ...)

... Maybe a never ending story ...

Configuration:

config.sh:

CAPTURE EXTRA PARAMETERS="-mean-value 0.3 -autoexposure 1"
KEOGRAM_EXTRA_PARAMETERS="-x -c"

GUI: activate "Auto-Gain"