Anything longer than 2 or 3 seconds causes the retval -108 issue. The interesting thing is that in every case it's always look for the filename of the last capture file. When I'm restarting a task list for 1 second exposures it's constantly incrementing the filename. It's only when I add a longer exposure does it seem to forget what capture file it's supposed to ask for.

The behavior is slightly different if I restart everything and start the first exposure with a 3 second or longer exposure. When I do that instead of seeing "Downloading //<capfile>.nef, I see "Download /", which of course fails and then different error codes (100 followed by a 107 I believe).

It's like longer exposures in the sequence queue lose track (or the Nikon isn't telling them properly) which capture file they were supposed to be asking for. Also, this happens when I use either FITS or Native node, that doesn't seem to matter. Probably also worth noting that in several of these cases I have to restart the camera to get back to a working state (once a capture retrieval problem occurs).

DEBUG 103.276850 sec : Setting radio/menu widget capturetarget: 0 (Internal RAM)
DEBUG 103.277192 sec : Setting new configuration OK.
DEBUG 103.277208 sec : Using camera predefined exposure ranges.
DEBUG 103.277216 sec : Finding optimal exposure setting for 1 seconds...
DEBUG 103.277223 sec : Best match: 1 seconds Index: 36
DEBUG 103.277230 sec : Setting radio/menu widget shutterspeed2: 36 (1)
DEBUG 103.297119 sec : Setting new configuration OK.
DEBUG 103.297214 sec : Using predefined exposure time: 1 seconds
DEBUG 103.297242 sec : Exposure started
INFO 103.297262 sec : Starting 1 sec exposure
DEBUG 104.297397 sec : Reading exposure
DEBUG 108.746417 sec : Exposure complete
DEBUG 108.746915 sec : Retval: 0
DEBUG 108.746929 sec : Downloading //capt0007.nef
DEBUG 108.760566 sec : Retval: 0
DEBUG 108.763691 sec : Downloaded 4928x3264 (preview 160x120)
DEBUG 108.764861 sec : Deleting.
DEBUG 108.764955 sec : Retval: 0
DEBUG 108.765050 sec : Setting radio/menu widget iso: 15 (3200)
DEBUG 108.765481 sec : Setting new configuration OK.
DEBUG 108.765578 sec : Setting radio/menu widget shutterspeed2: 41 (3)
DEBUG 108.820322 sec : Setting new configuration OK.
DEBUG 108.820415 sec : Exposure done, downloading image...
DEBUG 121.409137 sec : Requested CCD Frame is ( 0, 0) (1280 x 1024)
ERROR 121.409203 sec : Subframing is only supported in FITS transport mode.
DEBUG 121.409492 sec : Starting exposure (exptime: 5 secs, mirror lock: 0)
DEBUG 121.409511 sec : Mutex locked
DEBUG 121.409524 sec : Setting radio/menu widget iso: 15 (3200)
DEBUG 121.409917 sec : Setting new configuration OK.
DEBUG 121.409929 sec : Setting radio/menu widget capturetarget: 0 (Internal RAM)
DEBUG 121.410262 sec : Setting new configuration OK.
DEBUG 121.410272 sec : Using camera predefined exposure ranges.
DEBUG 121.410280 sec : Finding optimal exposure setting for 5 seconds...
DEBUG 121.410287 sec : Best match: 5 seconds Index: 43
DEBUG 121.410294 sec : Setting radio/menu widget shutterspeed2: 43 (5)
DEBUG 121.434852 sec : Setting new configuration OK.
DEBUG 121.435008 sec : Using predefined exposure time: 5 seconds
DEBUG 121.435052 sec : Exposure started
INFO 121.435114 sec : Starting 5 sec exposure
DEBUG 122.435205 sec : Capture in progress. Time left 4
DEBUG 123.435568 sec : Capture in progress. Time left 2
DEBUG 124.435777 sec : Capture in progress. Time left 1
DEBUG 125.436570 sec : Reading exposure
DEBUG 227.602508 sec : Exposure complete
DEBUG 227.602743 sec : Retval: 0
DEBUG 227.602972 sec : Downloading //capt0007.nef
DEBUG 227.603113 sec : Retval: -108
DEBUG 227.603222 sec : Downloaded 0x0 (preview 0x0)
DEBUG 227.603381 sec : Deleting.
DEBUG 227.603542 sec : Retval: -108
DEBUG 227.603643 sec : Setting radio/menu widget iso: 15 (3200)
DEBUG 227.604194 sec : Setting new configuration OK.
DEBUG 227.604364 sec : Setting radio/menu widget shutterspeed2: 41 (3)

I don't have this problem in gphoto, though it seems to reset the filename and doesn't quite have the same sequence queue capabilities as Ekos, unless one scripts it.

$ gphoto2 --interval=5 --frames=5 --force-overwrite --capture-image-and-download
Time-lapse mode enabled (interval: 5s).
Capturing frame #1/5...
New file is in location /capt0000.nef on the camera
Saving file as capt0000.nef
Deleting file /capt0000.nef on the camera
Waiting for next capture slot 1 seconds...
Capturing frame #2/5...
New file is in location /capt0001.nef on the camera
Saving file as capt0001.nef
Deleting file /capt0001.nef on the camera
Waiting for next capture slot 2 seconds...
Capturing frame #3/5...
New file is in location /capt0002.nef on the camera
Saving file as capt0002.nef
Deleting file /capt0002.nef on the camera
Waiting for next capture slot 1 seconds...
Capturing frame #4/5...
New file is in location /capt0003.nef on the camera
Saving file as capt0003.nef
Deleting file /capt0003.nef on the camera
Waiting for next capture slot 2 seconds...
Capturing frame #5/5...
New file is in location /capt0004.nef on the camera
Saving file as capt0004.nef
Deleting file /capt0004.nef on the camera

Can you list the full gphoto command you use to capture a 30 seconds frame? And If you repeat the command command exactly, does it capture the next 30 seconds frame and downloads the file?

EDIT: the command plus the full log from GPhoto like above

Sorry about that, my gphoto2 options were completely wrong. I can take 30 second exposures, but with probems:

I can set the 30 seconds shutter speed correctly. On the camera display it is going from previous settings to 30 seconds.

# gphoto2 --auto-detect --get-config=/main/capturesettings/shutterspeed
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,009
Label: Shutter Speed
Type: RADIO
Current: 0.2500s
Choice: 0 0.0002s
Choice: 1 0.0003s
Choice: 2 0.0004s
Choice: 3 0.0005s
Choice: 4 0.0006s
Choice: 5 0.0008s
Choice: 6 0.0010s
Choice: 7 0.0012s
Choice: 8 0.0015s
Choice: 9 0.0020s
Choice: 10 0.0025s
Choice: 11 0.0031s
Choice: 12 0.0040s
Choice: 13 0.0050s
Choice: 14 0.0062s
Choice: 15 0.0080s
Choice: 16 0.0100s
Choice: 17 0.0125s
Choice: 18 0.0166s
Choice: 19 0.0200s
Choice: 20 0.0250s
Choice: 21 0.0333s
Choice: 22 0.0400s
Choice: 23 0.0500s
Choice: 24 0.0666s
Choice: 25 0.0769s
Choice: 26 0.1000s
Choice: 27 0.1250s
Choice: 28 0.1666s
Choice: 29 0.2000s
Choice: 30 0.2500s
Choice: 31 0.3333s
Choice: 32 0.4000s
Choice: 33 0.5000s
Choice: 34 0.6250s
Choice: 35 0.7692s
Choice: 36 1.0000s
Choice: 37 1.3000s
Choice: 38 1.6000s
Choice: 39 2.0000s
Choice: 40 2.5000s
Choice: 41 3.0000s
Choice: 42 4.0000s
Choice: 43 5.0000s
Choice: 44 6.0000s
Choice: 45 8.0000s
Choice: 46 10.0000s
Choice: 47 13.0000s
Choice: 48 15.0000s
Choice: 49 20.0000s
Choice: 50 25.0000s
Choice: 51 30.0000s
Choice: 52 Bulb
root@jon-desktop:~#
root@jon-desktop:~# gphoto2 --auto-detect --set-config=/main/capturesettings/shutterspeed=51
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,009


This is a capture to the internal memory then immediate download:

root@jon-desktop:~# gphoto2 --auto-detect --set-config=/main/settings/capturetarget=0
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,010
root@jon-desktop:~# gphoto2 --auto-detect --get-config=/main/settings/capturetarget
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,010
Label: Capture Target
Type: RADIO
Current: Internal RAM
Choice: 0 Internal RAM
Choice: 1 Memory card
root@jon-desktop:~# env LANG=C gphoto2 --auto-detect --debug --debug-logfile=gphoto2-latest-internalram.log --capture-image-and-download
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,010
ERROR: Could not capture image.
ERROR: Could not capture.
New file is in location /capt0000.nef on the camera
File capt0000.nef exists. Overwrite? [y|n] n
Specify new filename? [y|n] y
Enter new filename: capt0000-2.nef
Saving file as capt0000-2.nef
Deleting file /capt0000.nef on the camera

This is a capture to memory card:

# env LANG=C gphoto2 --auto-detect --debug --debug-logfile=gphoto2-latest.log --capture-image-and-download
Model Port

---

Nikon DSC D5100 (PTP mode) usb:001,010
ERROR: Could not capture image.
ERROR: Could not capture.
Event FOLDER_ADDED /store_00010001/DCIM/101D5100 during wait, ignoring.
New file is in location /store_00010001/DCIM/101D5100/DSC_2315.NEF on the camera
Saving file as DSC_2315.NEF
Deleting file /store_00010001/DCIM/101D5100/DSC_2315.NEF on the camera

The gphoto2 logs are complaining about some kind of timeout. On the camera side I can hear the shutters immediately open, then wait 30 seconds then close correctly. Then a really long pause, then eventually the camera view screen will show the connecting to PC icon and a few seconds after that all of the ERROR output and everything after that goes to the terminal screen.

I'm seeing similar behavior in Ekos. When I try an expose it will take quite a while to download. Sometimes that means it will never download or the camera is just taking its time.

I'm going to escalate with gphoto2, since I'm running latest and still have the problem. If nothing comes of it, time to ebay this camera. Any sub $300 Canon suggestions that just work?

Yes, if gphoto can capture it without problems, so can we. If you can to go the Canon path, I can't recommend anything in particular but they pretty much most models seem to work fine.