Proper "rule" for pinpoint stars with M43

Giiba wrote:

OutsideTheMatrix wrote:

phil from seattle wrote:

OutsideTheMatrix wrote:

phil from seattle wrote:

yeah, astro...

However, I'll add my experience - I got perfect stars with 25 second exposure, 12 mm (24 mm EFL), f2.8.

Thanks- was this with Orion and pinpoint stars even when viewing 1:1?

I've not shot when Orion was up but no trails at all.

Thanks, I viewed your spreadsheet and came up with the following: 8 seconds at 14mm focal length (28mm equivalent) should be enough to achieve pinpoint stars. Have you found the same?

I see 15s when I punch in the FL and aperture, with a score of 183.

I'd be curious to know how it works out as I've very little idea of what the score really means photographically. I use a standardized formula so these score should be comparable across formats. So far my best results have been with the 15/1.7, I don't find the 8/1.8 picks up more stars but I've only gotten the fisheye out once for clear skies.

What does the score of 183 mean?  My very unscientific test involved just looking in the LCD of the camera post capture, but I magnified the view to 7x as I was told that simulates a 1:1 100% view on a 19" 1280x1024 monitor (not sure about that.)

My conundrum is this- I tried 8s, 15s, 20s and 30s.  30s has too much trailing so that's out.  8s has the least but 15s captures a lot more stars than 8s.  20s doesn't seem to capture more stars than 15s but the amount of trailing is the same.  15s/20s don't show trailing in the brighter stars of Orion (like in the Belt) but the dimmer stars seem to show trailing.  I think that's because the trailing isn't as perceptible in the brighter stars because they also appear to be larger?  If a post processing program like DSS or Sequator can fix minor trailing during stacking then I should probably stick with either 15 or 20s?

Also is there anyway to mathematically predict the amount of trailing in terms of pixels? Like (for example) is 15s at 14mm (28mm equivalent) going to result in less than 5 pixels of trailing?  3?  I want to keep trailing down to 3 pixels or less.