Igor PDML-StR wrote:
Larry, I haven't done much of astro-photography, so, I am just curious: why focusing at infinity wouldn't work in this case (i.e. turning the focusing ring to the end of the range)? Is it just because the particular lens(es) are not designed or manufactured well for infinity focus? (E.g. they have "beyond infinity" focus at the end of the wring range.)
Exactly. I've been told that "to infinity and beyond" is necessary for autofocus, although that doesn't seem true for my FA77. I suspect that it's just a lot less expensive to guarantee that a camera will focus past infinity than to carefully calibrate to go exactly to infinity. I wonder how much sample variation there is in registration distance between the mount and the sensor, as that would also affect the "infinity focus point".
Igor Larry Colen Sun, 04 Dec 2016 11:49:18 -0800 wrote: Jostein wrote: Your results are on par with what I've got from single exposures with the Sigma 500/4.5. Proper focusing seems to be the limiting factor rather than actual MTF resolution. Yes, focusing was a real challenge. If I remember to bring my green laser, I can aim that at a distant point and have something to focus on. I probably should have tried focusing on Sirius, it was a lot brighter.
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