larger area of sensor, not film. 99% of astrophotography is done with a CMOS or CCD camera, not film.

4K video = 3840 x 2160 = 8.3MP, my MILC = 8260 x 5512 = 45.5 MP. I'll stick with a conventional camera!

I developed the NEF with RawTherapee and applied very high contrast in GIMP and the grid is not reproducable. dropbox.com/s/qlpv83c4a3kremx/… I suspect, therefore, that your grid is related somehow to the software you used.

+1 for rejection stacking. I see starlinks in a few sub-exposures but they are eliminated in the final image. I have no plans to give up astrophotography.

@Tetsujin Not very likely: expertphotography.com/wp-content/uploads/2019/01/…

@MichaelC 100% correct and only 240% more expensive!

100% crop: mdavid.com.au/photography/100crop.shtml

I strongly reccomend that you use this instead: thousandoaksoptical.com "Used by NASA aboard the Space Shuttle. Other professional users include: ABC, BBC, CBS, NBC, CNN, NOVA, The Discovery Channel, National Geographic, and most major universities and observatories throughout the world." I use and endorse thier product. I had no damage to my Nikon D800 sensor or otherwise in the August 21, 2017 eclipse here in the USA.

As the camera faces the subjects, the flash is to the left and very slighly above the lens. As such, the flash will leave a shadow to the right. It doesn't matter which eye was used. It only matters that the flash is to the left of the lens as the camera faces the subjects.

Possibly related: How can I avoid star trails?

You will probably have some difficulty getting the squirrels to remain still for the ten or so shots required for focus stacking!

Therefore, in order to photograph something 1/4 mile away, you'd need to step forward 440 feet. It might be a bit difficult at the Grand Canyon.