Turning off daytime auto-exposure to use histogram exposure.

[Stephen2615]

Greetings,

I noticed the message "Turning off daytime auto-exposure to use histogram exposure." in the log and wondered why this happens when you have the option to turn on daytime auto-exposure if the histogram automatically makes the entry redundant.

I also notice that if the mean is high, the image is overly bright. I tried to determine how the mean is calculated but the info in the log doesn't give any indication. Camera is a ZWO 120MC-S just in case it has something unusual about it. I have turned the brightness down to 20 (even though the min is stated at 50) to remove the entry in the log when the system starts up. 50 is too high or so the ZWO message seems to indicate.

I have placed the histogram as far away as possible from where the sun transits across the sky. Is that a good or a bad thing to do? Endless cloud here doesn't help things all that much.

Thanks

Stephen

[EricClaeys]

@Stephen2615 ZWO cameras have a built-in auto exposure capability but we turn that off to use our own algorithm during the day, which tries to get the average brightness in the histogram box to be between 122 and 134 out of 255. Hence the reason for that message in the log file. You can ignore that message. Users can of course turn off auto-exposure during the day in which case that message doesn't appear.

Higher brightness numbers mean a brighter image, at least where the histogram box is. I moved mine on both cameras so the sun and moon would not go through them, making the picture dark.

The mean brightness reported by the software is basically the average (mean) of the brightness of all the pixels in the histogram box.

Different cameras have different minimum, maximum, and default values for many of the settings, including gain and brightness. The current WebUI doesn't know about those differences so allows you to enter anything but the Allsky software knows about the differences and displays a message if something is out of bounds. I hope to update the WebUI in the next release.

Hope this explains things.

[Stephen2615]

Thanks.
When using the manual exposure, it seems to be relatively happy with 300 us and a brightness level of 20. It depends on various things but it is a good medium value. It is not overly bright and I can live with that. When I turn on day autoexposure with the histogram as far away as possible from the sun's transit, I get wild swings in exposure and the mean also goes up and down sometimes over the allowable value for rejection. It is rare to get the same exposure and mean in two consecutive exposures from basically the same sky quality. Perhaps I should provide the log so you can check if anything is wrong.

[EricClaeys]

@Stephen2615 Yes, please make sure Debug Level is at 4 and you start with a clean log file, then after you see the daytime swings, attach the log file.
A couple things to check for:

• If you have auto exposure on, the turn off auto gain.
• Set USB Bandwidth to 40.
• Toggle ** Version 0.8 exposure.

Eric

[Stephen2615]

Thanks for the reply. I did a fresh install as I wanted a bigger sd card. and now the the software appears to be running happily. So far the mean is hanging around the 140 mark and the exposures are good considering everything. So fingers are crossed. I have moved the histogram box away from the sun's transit and right now, it is cloudy so the sun is overexposing a bit but I can live with that. I wonder if I somehow set Version 0.8 exposure off in the previous setup. I recall you mentioned it before. I have to stop playing with things.