Interval timer on 77D stopping after a few pics

[hoops1106]

I have a 77D and just bought a new wide angle 2.8/14 mm lens to take astrophotography pics.  I want to stack the shots for star circles.  I enabled the interval timer and set it for 99 pics with an interval of 3 sec.  All noise reductions are turned off.  ISO 1600 with a 25 second exposure.  manual focus.  

The interval starts out OK, does anywhere from 10 to 20 shots and then just turns off.  I have tried different intervals and different numbers of shots, but it does the same thing each time.

Any help will be much appreciated.

[Waddizzle · Accepted solution]

The interval time defines the time interval between attempts to automatically fire the shutter.  This means that your interval time must exceed the total time it takes to complete a single exposure.

Please note, the time to complete a single exposure includes the your exposure time, time to complete any noise reduction, and time to write the image file to the memory card.  

Some noise reduction settings cause the camera to capture a second exposure just as long as the initial exposure, effectively doubling the total time it takes to complete a single exposure.

[Waddizzle · Accepted solution]

The interval time defines the time interval between attempts to automatically fire the shutter.  This means that your interval time must exceed the total time it takes to complete a single exposure.

Please note, the time to complete a single exposure includes the your exposure time, time to complete any noise reduction, and time to write the image file to the memory card.  

Some noise reduction settings cause the camera to capture a second exposure just as long as the initial exposure, effectively doubling the total time it takes to complete a single exposure.

[Waddizzle · Accepted solution]

“   I enabled the interval timer and set it for 99 pics with an interval of 3 sec.  All noise reductions are turned off.  ISO 1600 with a 25 second exposure. “

This is your entire problem.  You need a 30 second interval time, or anything that exceeds the 25 second shutter speed, plus whatever extra time is needed to complete a single exposure due to noise reduction settings.

[hoops1106]

Thanks so much for the help. I really feel kind of dumb. But your answer makes total sense now and I am going to renew my attempts at star circles!