The attachments appear to already have been processed from a D750 down to 1620x1080 attachments. This limits the creation of a final result covering all aspects of a final edit (noise and sharpening ideas, for example). The EXIF data is incomplete to determine what software was used to create these attachments nor to determine the original format images (RAW or JPEG).

Personally, I avoid multi-shot exposures for the reasons that occur in these examples. Even asking people to be still, there is slight amounts of subject movement. Given the power of digital editing software, you can coax a great image out of a single shot rather than merging multiple images.

I used the 2nd from bottom version (normal exposure?) for this processing. It seems the image could use some sharpening, but that work should be performed on the original, not this 1620x1080 version. You mentioned having LR, try the adjustments below. The attached has been cropped, leveled and centered slightly.

The files are very small. The originals from your D750 should be much larger (assuming that you have it set to "Jpeg Fine" or whatever the maximum quality setting is).

When you upload the file from your Mac, do you have it set to "Export to internet" or some such? If you have, it'll shrink the file for uploading. A straight "Export" is what you need. Or just use the UHH browse function to go straight to the original jpeg file.

My advice would be to merge the middle three exposures, which should give you a relatively noise-free file with the data spread evenly across the luminosity spectrum. At the very least I would recommend excluding the brightest exposure from the merge.

Yes, there are a lot of challenges, and I won't be of any help on those, but there are folks here who know what they are dping for that type of photography.

By the way, if you click "quote reply" below the post to which you are responding that makes it easier to know to whom you are responding.

I am guessing that you are under age 70, which is good. We need more young people here. Don't let the grouchy old farts run you off!

Mike