Dark nebula photography is a wide range of exposures because they vary In brightness quite a bit. Nebula offer what I feel is the best color in astrophotography and why it is my favorite. Generally, this kind of photography will require the main telescope, a guide telescope, imaging collecting software, and automation of some kind. I used ACP for automation which connects to MaximDL and FocusMax. ACP moves the telescope to the object, center it, take the exposures, and focus the telescope as needed.
I usually use exposures of 300 seconds to 600 seconds and take anywhere from 30 minutes to 3 hours of imaging time. Nebula is mostly in hydrogen-alpha do very well using a black & white camera with a hydrogen-alpha filter. The color cameras have the advantage of just taking one set of images. The cameras that require color filters also need to take a set of images for each filter. The advantage of using a black and white camera with filters is the quantum efficiency is much better than a color camera.
I used a software package called PixInsight to calibrate the images, align, and stack the images. I use PixInsight for some post processing once a final image is created, however, I do most of my work on Lightroom Classic, Photoshop, and Photoshop plug-in. Nebulae because they vary so much can be one of the more difficult objects to post process, however, they make the most beautiful photo of any of the objects out there.
Be anxious for nothing, but in everything by prayer and supplication, with thanksgiving, let your requests be made known to God. Philippians 4:6