Night Landscape Experiment

Yesterdays failure in night sky photo pointed me towards Google. I found out that there's calculation rule how to shoot night sky:

Rule of the 600:
Full Frame camera: 600 / focal length =exposure time in seconds
Crop camera 600 / (focal lengths * crop factor = exposure time in seconds)

This results little star trails, but their not clearly visible in resized pictures. You can't make big poster or crop the photo, but it's good for web. Some say that 600 is highly optimistic and use 500 as base number.

What about ISO? Highest you can, but there was also calculation rule:

Full Frame camera: 6000 * f-stop^2 / focal length
Crop camera 6000 * f-stop^2 / focal length / shutter speed

Above calculations in picture: 2.8f, 24mm, 25s, ISO 1800 (bumbed a bit since Canon 6d is very good in low light photos)

What about picture itself? It's photographed in parking lot of a wheat field. On the left side of the picture there's gasoline tank for tractors. Top right int the holds The Big Bipper. There's some clouds and lights from City of Turku and Naantali.