Proper "rule" for pinpoint stars with M43

Giiba wrote:

OutsideTheMatrix wrote:

boxerman wrote:

offtheback wrote:

Great shot!

Thanks. We had to work pretty hard to get a good print of that shot. Screens are just very different for this kind of shot compared to paper. Glowing stars are much more visible on the screen. With paper, your top end brightness is very limited. Our final print, 24" wide, looks pretty good, but the stars are still not as prominent as with a screen.

I was wondering about prints! Is there a best type of paper to use for this kind of work?

I've done 24x18 prints that looked good on standard print shop paper, prefer the matte finish. Haven't done anything fancy, though I'm curious about prints on metal and canvas to see how they turn out.

I experimented the other night (my first seeing stars in months) with my 40-150/2.8 and found that 3.2sec was the max I could shoot without trailing @150mm when looking ENE. I have adjusted the formula on the spreadsheet to account for my findings. I am now reasonably happy with the max exposure time ouput as it gives a rough idea that can be used as a starting point for untracked exposures; increased when facing the pole, and decreased facing the equator. I have now tested 8mm (fisheye), 12mm, 15mm, 17mm, 150mm. Going to do some shots at 40mm'ish next chance I get.

How does that fit in with our findings of 10 sec at 14mm?

I saw this formula somewhere- what do you think?

Recently, I ran across this equation:

time = 240 / (lens fl * cos dec)

where dec is the declination of the star closest to the celestial equator. This over estimates the time so I've now modified it to the following:

time = 150 / (lens fl * cos dec)