I think I figured out my issue with the external timer.....I need the D500 set to bulb mode....then the external timer works fine....just finished testing that. And no I don't have and xqd card...can't afford one of those just yet only have the sd card.

I had double checked to make sure that I didn't accidently hit the bracketing button as well....that was my first thought...have no clue why the internal intervalometer does that but at least I got the external one working....now if I can stay up late enough tonight to try again!

Thanks for the help!

I need some help....I went out last night to our horse pasture to try to get some star trails....I set up the camera and Pixel Pro TW283 and thought I had everything correct to take 80 shots at 2 second intervals with a 30 second exposure.....NOPE.....after everything was done....I looked and I only got 40 shots...not sure why.

Here is my setup:

Nikon D500 with Sigma Sport 18-35 lens
Both camera and lens set to manual focus and lens set to infinity
Camera set to 30 second exposure F2.8 ISO 400
White balance set manual to 4500k
Raw
Center weight meter
Sandisk Extreme Pro 170 mb 64 gb card (formated for the evening so it is empty)

Pixel set to:

Delay - 5 seconds
Long - 00 00 30 --- for 30 second exposure
Intvl - 00 00 02 - for 2 seconds between shots
N1 - 80 -- total number of shots wanted
Repeat - 1
N2 - 01

So I hit the button and the camera starts....it sounds like it's going off every 30 seconds -- so I walk away and watch my Pixel reading....it's counting down like it should.

Once it all stops I head home and go to take the pics off the camera and I only have 40 shots instead of the 80.....anyone have a clue as to what I did wrong?

Looking at the Pixel today and watching what it does it goes like this:

I hit the start button - the delay counts down - then the screen goes to the Long with N1 flashing and the screen shows 80 (flashing) 00 30 (counting down), screen gets to 0 and switches to Intvl with 2 counting down - then goes back to Long N1 and 79 and starts all over again. As the counter is going the camera is clicking:

Once the delay gets to 0 the camera clicks and is engaged to take the shot - now when the Pixel gets to 0 for the first shot and switches to Intvl and starts counting down 2 -1 and that's when I hear the next click.

So to me it looks like it's working fine but it's not and I am baffled as to what I am doing wrong. Can anyone help me get this working correctly?

Here is the shot with just the 40 pics.

So I also tried with the internal timer on the camera and set it as follows:

interval 00 00 05 - for 5 seconds between shots
No of Intervals x shots/interval = 25 x 1 = for a total of 25 shots
Camera still set to 30 second exposure

Start now....the display shows 25 1F....so that should mean I get 25 shots right? As it's going...it doesn't sound like it is waiting the 5 seconds....as soon as the shutter closes, it opens again. Intervl is flashing on the display starts out at 25 1F on first shot, then goes to 18 1f on 2nd shot, then to 11 1f on 3rd shot, then 4 1f on 4th shot and then done and it stops! No more shots taken......I can't figure this out!

I use a D500 for star trails several times a year but as an alternative to using the in camera intervalometer I set my camera to continuous shooting mode, set my exposure to 30 sec, and lock my cable release to "on", set my stop watch to how ever long I want to shoot which is usually close to 2 hours to get nice trails. When the time is up I turn off the cable release lock and the camera stops shooting. I use an XQD card, I shoot RAW manual mode, usually iso 100 for star trails and there are no buffering problems. I get up to 380 exposures to stack and it works without a problem every time. Give it a try and see if it works for you.