Hello
Would like to record northern lights with 4 cameras in winter. Take 4 images per second at an interval of 0.25 seconds with an exposure time of 0.5 seconds. How many ProTimers do I need and can I set them all like this?

Take 4 images per second at an interval of 0.25 seconds with an exposure time of 0.5 seconds.

Shooting with an interval of 0.25 sec with an exposure time of 0.5 sec. will not work. the interval can not be shorter than the exposure time.
The interval time = exposure time + dark time. Dark time is the time where the camera needs to write the picture to the sd/cf-card. Did you check how fast your camera is? This will give you the minimum dark time.
Not sure why you want to use 4 cameras. In theory the LRT-ProTimer can handle 2 cameras with the same settings at the same time. So 2 Timer would be OK, depending on the cable length being available.

I'm already aware of that. That's why the time delay....hope you understand what I mean....

1. Camera 0.5s Exposure, delay 0.25s, 2. Camera 0.5s exposure, 0.25s delay, 3. Camera 0.5s exposure, ........

This post was last modified: 2023-09-24, 11:08 by Gunther.

I think what you want to do is set the Exposure to 0.5s and the interval to 0.75 or 0.8 Seconds (which always includes the exposure time). Let's please stick to the right terminology.

Interval = Exposure + Dark Time

You need to test if your camera is fast enough to do this.
Check out the Manual for the LRT PRO Timer: https://lrtimelapse.com/lrtpt/manual/
section "Fine Tuning the LRT PRO Timer to your camera".

Hello Gunther
I understand that about the dark Time. But I think you still don't understand what I want. I know that Icelandic photographers do that. Need support now. If the Pro timer 3.0ndoesn't do this, you could also install a delay in the cable?...

What do you call "delay"? What happens after that 0.5 sec exposure?

Since 4 cameras record, each camera has 1 second, which is enough for 0.5 seconds of exposure. Do not understand your question?

3 cables with 250ms, 500ms and 750ms Delay,,,,

This post was last modified: 2023-09-24, 16:53 by Gunther.

So if I understand you correctly, you want to synchronize those 4 cameras so that each trigger 250ms after the other?

Frankly I don't see why this would be useful for northern lights photography.

This is currently not supported by the LRT PRO Timer.

For two cameras you might be able to achieve it by misusing the 2nd port in Motion Control Mode, and mess with the the delay time, but I've never tried that.