Hi Everyone, I am a longtime user but a first time participant in the forum. I'll be doing some 24 hour TL soon and prefer using the ND 3.0 filter during the day to mitigate movement of plants and trees (to get a slow shutter speed). I also prefer to hold my aperture consistent throughout the sequence and get correct exposure via ISO, shutter and ND filter. Does anyone have a suggestion about the best approach to remove the ND as twilight sets and also to return the ND as the sun rises. Thank You.

Of course I understand the need for long exposures during the day and shorter during the night, but generally I do not recommend removing ND filters while shooting. What will happen ist that you will remove the filter then the next exposure will be overexposed by 10 stops if you don't manage to reduce the exposure by 10 stops in the same interval that you remove the ND filter. With useful intervals of <15 sec this is impossible IMHO. And even if you would manage to do it, you'd get a color shift between the images with and without ND which will be hard to impossible.

Generally for day to night where I want to capture all the way to the milky way I bite the bullet an work without ND.
In urban situations with artificial light, I use a 64x ND which I leave on all the time.
Apart from experimenting for practical use most of the time I find 24hrs timelapse quite long and boring for viewers, so that I prefer to do shorter ones with only a subset of the transition - this also allows me to chose the strength of the ND and whether or not to use it at all.

I agree completely about a 24 hour TL being boring but this is a specific request for a job coming in a couple weeks, so I will need to choose an approach. I have struggled with removing the filter and getting the exposure back on track during the interval--best for me has been dropping a couple of frames while I get the exposure back on track-- and also been disappointed with the results of changing aperture during a long TL--for me, at least, the F-stop changes remain visible no matter how much time I invest into post production. Maybe the answer remains right where I am already, it's a challenge but also it will be fun. Appreciate your thoughts and continued improvement into LRT. I've been a user for some time and it keeps getting better and better.

Yes, unfortunately that's something not really fully solvable.
Thanks for your feedback!