|
A strainer is like a Bahtinov mask, using diffraction to find focus. Bahtinov's work well on large aperture long FL optics but not so well on short FL wide angle lenses. I usually point my camera at the pointers or another bright zero mag star. I centre then set the live view to 16X magnification. I focus the bright star then look around the field for appearance of faint stars. When the fainter stars appear brightest, that is best focus. It doesn't work in some older consumer level cameras if the LV of the sensor doesn't have adequate sensitivity to show the stars.
I have taught this method in my nightscape workshops for many years and as camera sensors have improved over time, more and more participants cameras can now utilise this method. It's been a while since anyone turned up with an 810 but I had two 850's last year that did this easily. Your D810 sensor LV should have more than adequate sensitivity to use this method.
I've been camping at Kati Thanda Lake Eyre NP up in the north of SA at the moment, nights are quite warm around +5C - +8C. Home in a couple of days....Brrrr.
Cheers
Joe
|