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I discovered gphoto2 a couple of days ago and I've been digging into the documentation but I've not been able to solve my problem.

I would like to create a star trail with my Nikon D3400. The camera should take a sequence of shots in bulb mode (exposure time 2 minutes). Ideally, there should be as little off-time as possible between two different shots. I would also like to save the frames into the camera SD card.

The command I have assembled so far is:

gphoto2 -F 30 -I 1 --set-config bulb=1 --wait-event=120s --set-config capturetarget=1

Break down:

  • F 30 sets the number of frames to shoot.
  • -I 1 sets the interval to 1s.
  • --set-config bulb=1 activate bulb mode.
  • --wait-event=120s shoot for 2 minutes.
  • --set-config capturetarget=1 save the picture to the camera SD card.

Unfortunately, it only takes one shot, then it exits without giving any errors.

What am I doing wrong? Is it even possible to take multiple shots when using bulb mode? Are there any other approaches to achieve my goal with a PC connected to the camera?

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  • May I ask why you don't want to use a dedicated intervalometer? Say, one that you could set up prior to (such for 2 minutes), and then trigger them from your computer. I'm curious, not stating that this is a better choice than what you're desiring to do. I certainly understand wanting to know the how and why for a particular task, not necessarily the 'easy'.
    – J.Hirsch
    Feb 12 '20 at 20:58
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    No reason in particular, it's just that I have a raspberry that I currently don't use and I could turn it into a camera controller: this may be even better than an intervalometer as I could also write bash script to take multiple EV shots for HDR (D3400 is an entry level camera and doesn't provide that option). To connect to the raspberry I use VNC (from my phone, setting it to be an hotspot wi-fi). Then I select the proper script to launch: each script is using zenity that allows me to easily insert the values I need (such as shutter speed, iso, number of frames...).
    – Davide_sd
    Feb 12 '20 at 21:12
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    Ahhh, I see. Excellent Reason there! I'm sure you've done lots of homework; may I suggest reading up on HDR and mechanisms ? And if you're willing to put in a little back-breaking labour, you can go back to doing stitching manually with PT-GUI and whatnot (doing HDR Panoramas the hardway). That'll give you solid foundations for how and what's done now.
    – J.Hirsch
    Feb 12 '20 at 22:51
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You can try to do the task by explicitly define loop and interval:

for i in $(seq 1 30)
do
gphoto2 --set-config bulb=1 --wait-event=120s --set-config capturetarget=1
sleep 1
done

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