Lightning pictures ?

[Fish31520]

Hi there,

I was wondering if there could be a way to use or to tweak Allsky's parameters to take pictures of lightnings.

Or may e could you recommand me a similar project on this topic ?

Thanks for your help !

Jean

[aaronwmorris]

For the most part, capturing lightning is really just about luck.

The primary problem with capturing lightning is that most cameras that are used with all sky cameras are "rolling shutter" types. Most lighting occurs so quickly, the camera will only be able to read a percentage of rows from the sensor before there is massive changes in brightness, which results in horizontal banding effects. Some lightning has slow enough "action" that it can be captured properly with a rolling shutter.

This is an example of the rolling shutter effects when capturing lightning: https://en.m.wikipedia.org/wiki/File:Lightning_rolling_shutter.jpg

The alternative is a global shutter camera like an ASI174MM or ASI432MM (or Raspi global shutter IMX296), but those are monochrome. A global shutter camera would have a much better chance of capturing a clean shot.

I managed to get extremely lucky a couple of years back. I have a single shot with lightning and stars in the same frame.

[Fish31520]

Hi @aaronwmorris,

Thanks a lot for all those explanations, that's very interesting and I didn't know it !

In that case, if the problem comes from the camera, could I use a different kind of camera (still compatible with the RPi), with a different sensor ?

Thanks !

[aaronwmorris]

Global shutter type cameras would technically be better because they read the entire sensor at once instead of a rolling shutter which reads each row of the sensor sequentially which can cause the artifacts with very fast changes.

https://en.wikipedia.org/wiki/Rolling_shutter

Raspberry Pi has a IMX296 global shutter camera that could be used. I believe it is compatible with TJ's Allsky, but the team here would have to speak to that. The drawback to the IMX296 is it is monochome and the maximum exposure is 15.5 seconds which might be less than ideal for an allsky camera. I do not know if I would dedicate a camera for this unless all you were interested in was lightning.

https://www.raspberrypi.com/news/new-raspberry-pi-global-shutter-camera/

I know a few people have built allsky cameras with the ASI174MM, but I think that was because they happened to have the camera on-hand, not for a specific reason. The ASI174MM and ASI432MM cameras are relatively more expensive than most planetary cameras, because they are special purpose cameras for Solar and Lunar astrophotography.

[chvvkumar]

With long enough exposure and a bit of luck, you can capture lightning. A problem you will run into is, lightning accompanies rain and the water drops will distort the image. This is from my AllSky camera:

[Fish31520]

Very nice picture ! The rain drops give a certain effect !

In fact, my idea was not to use exactly my Allsky setup but maybe a RPi camera inside my house, sticked to a window, protected from the rain by a canopy (or something like that 😅).

In fact, you're right, a long exposure (maybe there is a tool for that in RPi OS ?) with a global shutter camera could do the job !

[chvvkumar]

I found this for using libcamera to take repeated long exposures.

raspberrypi/picamera2#343

[Fish31520]

Perfect, thanks a lot !

I'll try that on the next stormy night ! 😄

👋