I use Lightme and the companion note app Logbook (which you need to get through the iPhone app beta program). It's got some reciprocity calculations...
I've found fresnels counterproductive and distracting. The right amount of grind on the glass will provide both comfortable viewing as well as allow...
Mr. Shiu is correct- you remove the front group of the 150mm Symmar to make it a 265mm lens. Opinions vary on the optical quality of the rear element...