Is Asymmetrical out-of-focus a problem w/ ND800's?

[Daveskywill (David)]

Hi everyone:

I have a Nikon D800 DSLR, and haven't received sharply focussed photos

with it yet.

And Nikon on the net, there is an admission that the Auto focus with it

might be out of whack but you know that I will not use that during astro

photography. It was just what came up on a search on the net.

So asymmetry out of focus shouldn't be problem in "Manual" mode, should it?

But here is my Moon photo about 3-4 days ago during gibbous phase.

And it represents what all my astro photos look like, a little out of focus.

Is this a good source? :

http://www.astropix.com/HTML/I_ASTROP/FOCUS/METHODS.HTM

How do I use a Ronchi grating on my scope. I've got a Batinov mask

and a small Ronchi grating I think 100 lines per inch and 1"X2".

Maybe I'll try using parfocal eyepieces.

Thanks.

David

[Daveskywill (David)]

The Nikon should be alright in manual mode, should it? because

the article says that the asym out of focus is just in its auto focus

sensors: http://photographylife.com/nikon-d80...ic-focus-issue

I wish to get this ironed out

thanks

[RickS (Rick)]

Even if your camera has this problem (only a proportion of the early production units did) it won't have any impact on manual focus.

Cheers,
Rick.

[doppler (Rick)]

I am not sure that focus is the problem with your moon shots. I think that atmospheric turbulance is more likely the culprit. I have not had much luck producing a crisp shot of the moon or planets with a single shot even though they look sharp in live view at 10x zoom. I have noticed that most of the great shots posted here are done with stacked video files and not DSLR's.

Rick

[raymo]

Hi David and Rick, SLRs and more recently DSLRs, have never been the camera of
choice for
lunar work, due to mirror, and or, shutter vibrations. Using a
remote shutter release doesn't help with those problems. Mirror lock up
does help, but you are still left with shutter vibrations.
If you are using a Bahtinov mask your focus should be spot on. If your
unsharp images are indeed due to the aforementioned problems, it is
easy to fix it. You will need to experiment with a few shots depending on
the phase of the moon. Set a very high shutter speed [say 1/3200th or
1/4000th of a sec.]. Set ISO to 1600, take a trial shot, and correct for
over or under exposure by using lower or higher ISO as necessary. This
will give pin sharp images, as the exposure is over before the vibrations
can affect the image. Don't worry about the high ISO affecting the quality
of the image; it doesn't, at least my old eyes can't see any effect. Needless to say, you must use a remote shutter release or a time delay, as has already been mentioned,the slightest touch of the camera will ruin the image.
Hope this helped.
raymo