[interested_observer]

Use this simple calculator to determine the best exposure to start with for photographing the Milky Way.

• Milky Way Exposure Calculator – Lonely Speck

[Docrwm]

Interesting. My Sigma 30/1.4 on my K-5iis results in the following settings:
Shutter Speed: 11 seconds
f/number: f/1.4
ISO: 3200

But my Vivitar 85/1.4 yields the following:
Shutter Speed: 4 seconds
f/number: f/1.4
ISO: 12800

The website Lonely Speck is very useful. Learned why my 30/1.4 is probably my best lens for astroscape photos from a good article here: How to Pick a Lens for Milky Way Photography – Lonely Speck

I went ahead and did calculations on my main lenses likely to be used for Astroscapes based on the article parameters. I have developed a chart of those lenses, many of which are common to users here, including name, f setting, ISO, shutter speed and the Astro Lens Score they use to rate lenses for this purpose. I have noted in 3 instances the possibility that the settings will result in star trailing. The authors suggest that lenses rated 1000+ are most likely to produce excellent Astroscapes. Seems I have two - both are f1.4.