#underexposure

I've been trying to capture some stunning astrophotography shots with my Canon EOS 5D Mark IV, but no matter how I adjust the exposure compensation, I find myself consistently underexposing my images when using the Tamron 24-70mm f/2.8-4 Di VC USD lens in low-light conditions. I've checked the lens's aperture and shutter speed, and they seem to be within the optimal range for capturing low-light shots. I've also tried using the lens's built-in image stabilization feature, but it doesn't seem to be making a significant difference. Has anyone else experienced this issue with this particular lens and camera combination? I'd love to hear about any workarounds or solutions you've found to address this problem.