It's probably a moot point because of the vignetting.
You realize that the entrance pupil that defines the aperture is inside the lens, right?
People here are talking about vignetting - but there is likely very little vignetting caused by increasing field angle because it's the exit pupil - and its location - that matter. In dslr lenses the exit pupil is pushed far away from the sensor optically - so there is much less tilt in field angle than people expect.
Instead of vignetting there will mainly just be a loss of aperture across the field - and that won't show in the image at all if you expose long enough. That's why so many people try fast lenses with narrow filters and say they 'work.' Well - they certainly should work, but at reduced aperture.
For some dslr lenses you can find out where the exit pupil is located and use that to estimate how much actual vignetting there would be. But even in the center of the field, where no vignetting is possible, there will be reduced aperture and throughput at f/1.4. And to make things worse - that reduced aperture only affects the nebulosity signal you are after, while the sky background still comes through at full power.
I created a tool to show how vignetting behaves with different exit pupil distances. Note that the size of the exit pupil could be anything - including infinity - even with a very slow lens. That's because its size and location are determined by the optical design - and there are benefits to pushing the exit pupil far from the sensor - particularly for wide field lenses.
Here is the thread and tool that somewhat explains this - and you may be able to find the parameters for your lens:
Note that hyperstar is an example that appears to have the exit pupil at infinity so there is no increased tilt as you move away from the center - even though it is f/2.