Which of these looks sharper/better to you?

Started 2 months ago | Polls thread
TheSonyEnthusiast Regular Member • Posts: 259
Atmospherics or periphery was just out of focus

StefanD wrote:

TheSonyEnthusiast wrote:

kiwi2 wrote:

TheSonyEnthusiast wrote:

The first shot is mine and I think the reason the first photo has the moon periphery out of focus is because teleconverter shrinks the already narrow depth of field of the 70-400.

I don't think you'd be having a DoF issue with something 400,000 kilometres away. It looks more like motion blur. Don't forget the moon is constantly moving across the frame unless you are tracking it on a EQ mount.

With the TC the f-ratio become slower and it exaggerates lens softness. What was the ISO and shutter speed?

While I will admit the shot was at 1/20 of a second, if it were motion blur it would affect the sharpness across the entire image. The reason I think it may be depth of field is due to the preciseness necessary in manually focusing; I took a series of shots barely nudging the focus each time toward infinity, and a fraction of a millimeter either way resulted in less resolved craters.

According to this DoF calculator, the DoF of a 600mm lens at f/8 focussed at the moon (384402000m) ranges from 1500m to infinity. That should be enough to have the whole moon in focus.

Looking over the series of photos I shot, I noticed some shimmer attributable to atmospherics between photos, along with focus.  Given the face of the moon is 'slightly' closer than the periphery, the photo I took may have had the face *just within* focus that could result in the softer periphery, or it may have been due to atmospherics.   This shot was one of the earlier shots in the set, and I do have others where I got more and even all of the periphery in focus.

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