The lens is a Pentax DA 560mm F/5.6 ED HD AW with a KP attached to it.

It seems fuzzy in the middle, sharper at the edges, to me. Like it's back-focusing. (Since the edges are obviously farther away from the camera than is the center, which is what I was focusing on.) That's with ISO 100 and f/11.0, which ought to optimize for sharp images well enough, I would think.

I've tried focusing the thing manually and automagically, each with both live view and the viewfinder, and this was the very best I could get.

I had one of these lenses before (some may remember the tale) and sent it back because it couldn't focus clearly on anything at any distance - the best it could do was still fuzzy, nothing really in focus at all.

This lens is better than the previous "copy", but it still seems like a "shouldn't happen situation", to me. Especially after seeing all the razor-sharp images coming out of other folks' cameras with the same lens (https://www.pentaxforums.com/forums/122-lens-clubs/282825-da560-lens-club-le...me-photos.html).

What do y'all think?

[DeadJohn]

The photo looks ok to me.

The moon is not an ideal test for lens sharpness. Atmospheric conditions can cause portions of the moon to come in and out of focus, or appear to wiggle. The full moon lacks contrast, too, except at the edges.

For photographic purposes, the entire moon is at infinity focus because it's so far away. Backfocus won't affect the edges and the center differently.

[MossyRocks]

To me it looks a bit underexposed and from the EXIF info it would appear to be so (about 2 stops under loony 11: ISO100, f/11, 1/100s). With a shot like this depth of filed wouldn't matter so I would assume that the f/11 was for CA control and I'm not seeing any of that, or was it to deal with a slightly off focus which I can guarantee you had unless you used a focusing mask. For a shot that is a day or 2 past full moon this isn't bad. the lighting in the center is the same as that harsh midday sun so there just isn't much detail or contrast to be had as there aren't any shadows. Another ting to consider is that the atmosphere is fairly turbulant which can cause areas to be out of focus which may also be a contributing factor to your perceived lack of sharpness.

You said you focused manually using live view but did you have focus peaking turned on? If I don't have a focusing mask when doing astro shots I will use live view with focus peaking turned off and then do star minimization. Having focus peaking turned on will bloat the star you are focusing on so it becomes harder to get that perfect focus. This will get you really close if done carefully, and it will be much closer than autofocus will get you but it will more than likely be off slightly unless you are just lucky. Typically I use a bahtinov mask after minimizing a big bright star to really get the perfect focus. There are generators for them that get you a svg image that you can convert to stl file that you can get 3d printed. Once perfect focus is achieved I then frame up the object I want to shoot (they are all at infinity, even the much closer moon, from the lens's perspective).

When it comes to moon shots I usually start with a loony 11 equivalent exposure and do a quick test shot and adjust from there adding exposure until I get close to clipping the highlights. Then I blast away in burst mode hoping for the lucky shot.

Here is a shot I took of the full moon last month and it also shows the very flat illumination in the middle. 400mm ISO 200, f/2.8(wide open), 1/640s and it is a bit overexposed. This was focused using star minimization as I didn't have a focusing mask for this lens yet:

To bring out some the detail in the center I use unsharp mask but I still haven't figured out the best settings for using it on the moon so I got some haloing.

[HoutHans]

I second the extensive comments above; the moon is not the best spot to test the performance of a lens in light of the seeing and the picture looks quite good to me. You're better photographing a distant wall in non-turbulent conditions if you want to test that lens.

[MossyRocks]

You're better photographing a distant wall in non-turbulent conditions if you want to test that lens.

Also make sure it is cool out otherwise you get the heat distortions coming off of the ground.

[BigMackCam]

I've moved this to the lens discussion forum for better visibility

[kiwi_jono]

While its a pretty good photo, I think if it was shot at f8 (rather than f11 which will also starting to show some diffraction) and keep the same shutter speed would be a good starting point. Certainly the shutter speed seems about where it should be to avoid movement.

Thank you so much for your observations! As you may have detected, I'm not much on either super telephoto lenses or photographing astronomical phenomena as yet, and I need all the help I can get (a general statement not limited to photography).

[BigMackCam]

Honestly, the amount of detail it has picked up is decent enough. I'm inclined to think this is more a case of the phase of the moon and possibly atmospherics at play, rather than a focusing problem or poor sharpness from the lens.

I have dozens of moon shots taken at different times and in different conditions with the same lenses, and the results can vary hugely. Clear, cold winter nights with the moon high in the sky and stars that aren't twinkling will generally give very good results if you're just photographing the moon. The phase of the moon makes a huge difference... Full moons tend not to have enough natural contrast to make them interesting as they're very directly and evenly lit. You're much better off with a significantly waxing or waning moon to emphasise the surface details.

[StiffLegged]

Atmospheric effects are a big problem with long lenses, so I'm with Mike and MossyRocks. Have you played with the image in post-processing? I had a quick try in PS with the forum image and it immediately looks better to my eye. However, notice the better detail on the moon's rim between 12 and 3 o'clock (upper right quadrant) due to the low angle of the sunlight to the lunar surface? Shoot away from the full moon for better detail.