I'm looking to do a pretty large stitched mosaic of the Milky Way under Bortle 1.5 skies.
I will be using a Sigma 35mm f/1.4 Art lens on an unmodified Canon 6D mounted on an Atlas EQ-G, and potentially guided. I know... sounds overkill.
I'm thinking about stopping down to F/2 to eliminate the coma in the corners. ISO will be somewhere between 400 and 1600. And I will be stacking.
Right now I am thinking F/2, 150 sec, and ISO 800 for each panel.
My question if you were doing a tracked, and potentially guided shot of the Milky Way under a Bortle 1.5, what would your ideal exposure settings be ?
I should add this is for a mosaic shot of the sky only; no foreground. The idea is to get the exposure right so I can pull out as much detail of the Milky Way as possible in processing, but not overbloat the brightness of the stars.
I do a lot of crazy high-ISO astro video at 1/30s exposure realtime.
One thing I can lend from my experience that will come into play,
whether in large or small ways,
is the variance that I experience with regard to sky conditions from the same location that I can see changes that long exposure equation....
And by sky conditions I mean the water droplet content and dust/debris content in the air that can vary from night to night..
Seems like a no-brainer but my gear gives me the luxury of noticing this visually realtime in my live display...
With dark skies you will benefit greatly as the airborne particles will less reflect any light pollution,
and you are less at a risk of the sky approaching the point of blow out,
but be aware this variance can cause differences that you may not notice that night but back in the processing room while zoomed in,
you may notice things..
So it doesn't seem like you expect a magic setting,
but with some of the advice above the better plan is to assess the conditions and adjust given what the sky offers....
So the other unorthodox thing I'll leave you with:
In getting proper exposure, I like using a waveform monitor:
Digital Photography Review discovers the waveform tool:
But instead, you could pre-plan particular bright stars that will be in the frame and can shoot a test shot,
upload it into your laptop,
and then crop to the particular stars and look at their isolated histogram in PS**.
Or you could use the eyedropper to reveal the individual pixel values associated with those bright stars to give you the best baseline for where your exposure will be
***[of course you need to have an idea of where your stacking and processing lead in adjusting a RAW,
since you have to debayer an image to see its histogram or pixel values in PS...
Otherwise you could do the same assessment with RAW with particular tools in your stacking software, esp. PI or Rawdigger, etc........
Just random thoughts for the over-kill minded