Problems shooting the moon with EOS 90D

[Ramsden]

Hi folks from the North of England

Tuesday, this week, we were due another special big Moon, but the forecast predicted clouds, and they were right.

But on Monday, we had clear skies so here we go. My biggest lens (70-300) on my EOS90D and point at the Moon as it rises into the sky. The zoom was fully extended and I decided to try aperture priority f4-5.6 because I wanted to catch some trees and the church spires in the foreground. I was on autofocus and when I pressed the AF button the camera made a wirring noise and the size of the moon shrunk in viewfinder - but in focus. 

To keep a long story short, I was a bit confused and wasn't sure what had happened. So last night (we had another clear night) and went out again, but this time on M and Manual focus. I was able to get a bigger Moon in my view finder, but failed to get a clear focus. It was very fuzzy around the edges, and I went back and forth with the focus ring to no avail.

So, I feel I'm putting my head on the block asking a dumb question - but what is scientific, mathematical or physics reason for this occurence. Why can't I just zoom out and focus?

The 1st photo is of the foreground with trees and church - i went to a better place in the evenings.

The 2nd is from Monday with AF with clear outline and you can see the lunar landscape.

3rd is last night with MF

 

 

 Thanks as ever 

Ramsden

[jrhoffman75 · Accepted solution]

The moon is illuminated by the sun. Starting point for exposure would be the Loony 11 Rule f/11 with shutter speed 1/ISO. For example f/11, ISO 125, Tv 1/125.  

[wq9nsc]

The depth of field (closest to most distant object that is still within focus) is based upon your aperture and your distance from the objects.  With your 70-300mm lens choosing f8, with it zoomed to 300mm and you standing 100 meters from your subject, then objects that are between 86 and 119 meters away will be in focus.  If you change your focal length to 70mm, then subjects between 25 meters out to infinity will be within critical focus but of course the moon will appear quite small.

As to manual focusing, there may well have been more "atmospherics" at play when you were attempting manual focus and atmospheric conditions (high level moisture, smoke, temperature inversion layers) will prevent an extremely sharp image of a distant object even when it is perfectly focused.  Many zoom lenses require refocusing when dramatically changing the focal length.  They are complex beasts with a lot of moving and fixed components for both "zoom" and focusing and it isn't at all unusual for the focus to need correction when changing focal length.

For the moon itself to be sharp, you need to be fortunate enough to have great viewing conditions at your location and as photographers we can't control the weather.  The attached photos were taken several years ago with my Canon 1DX III attached to the Celestron CPC 1100HD telescope when the conditions were pretty much perfect.

Rodger

[Ramsden]

Thanks Guys - that's really interesting. I'd never heard of the Loony 11. More research, practice and learning for me. Great shots of the moon.

Thanks again

R

[BigAmericanHand]

If you want moon pictures, why not just get them from some astronomy website?

[kvbarkley]

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@BigAmericanHand wrote:

If you want moon pictures, why not just get them from some astronomy website?

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Where is the fun in that? It is like George Utley using the images that came with his frames because he did not have any family.

[Waddizzle]

Using a tripod and turning off lens IS should produce much better results. 

[kvbarkley]

Also, to get the shot you want you will most certainly need to do a double exposure and expose twice. Once for the foreground and once for the moon. Since the moon is a sunlight object, to get detail you need much less exposure than the foreground churchyard.

[Ramsden]

That makes perfect sense and explains why the church and trees didnt stand out.

I'm glad I asked the question now. You guys always deliver!

[Ramsden]

I should add that I was expecting someone to tell me to get a much bigger lens. But the shot I have in my head is meant to be 'spooky' with the church spires and trees - not a full blown moon.

Thanks guys

Ramsden