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10-07-2019, 07:50 AM   #1
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Photo analysis help please
Lens: Polaris 55~300 Camera: K-01 Photo Location: Oregon 

I got a Polaris 55~300mm f4.5 in a kit. Just for fun, took snaps of the moon last night.

I have great enthusiasm for doing this sort of thing, but very little technical expertise.

I'm greatly pleased with the image quality in the center, but puzzled by the fuzziness on the outer edge of the moon.

Is it due to:

- over exposure
- other photographer error
- duh, it's an old aftermarket zoom

Thank you in advance

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10-07-2019, 09:03 AM   #2
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Hi Banskojoe, I've had similar problems with a Sigma 150-400mm. It might be depth of field, or even slight movement of the moon. Also getting exposure right is difficult because the moon is quite bright. What ISO, f stop and shutter speed did you use?
10-07-2019, 10:14 AM   #3
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ISO 400, shutter speed 350, f4.5
10-07-2019, 10:51 AM   #4
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The fuzzieness appears to be from a missed focus, notice the green halo on the right of the image that is usually a tell tale sign of this. For astro shots depth of field doesn't matter. It may not have been off by much as you are getting pretty good but soft detail in the moon it self. I don't know what the atmospheric conditions were like (haze, humidity, smoke, etc) and if this has had post processing to bring things down but given the settings used it would appear that this may have been an overly bright moon unless there was a lot of stuff in the air.

To improve moon shots I usually suggest the following:
1. shoot off of a tripod
2. Focus manually on a star first using magnified live view without focus peaking turned on as you want to minimize the star size. If you have a bahtinov mask (useful focusing mask for getting a perfect infinity focus) use that
3. The default settings I start with is the loony 11 rule. So use some settings that get you the same exposure value as ISO 100, f/11, and 1/100s. From there you will likely have to add some additional exposure to compensate for haze, humidity, smoke, dust, polluiton, etc unless you have really clear clean skies. Typically I find I need 1 to 2 stops extra unless I am shooting in the cold winter.
4. Don't shoot wide open stop the lens down 1 or 2 stops to get the best sharpness
5. Shot lots of frames and pick the best one. The atmosphere is rather turbulent so shoot a bunch bin the bad ones and you may find one where you have a really still moment captured.

The moon is really bright and it moves across the sky slightly slower than the stars do so shutter speed is rarely an issue with its movement in the night sky but to prevent issues from mirror slap or camera shake you still want to keep it up around 1/focal length.

Here is one of the moon I did about 3 weeks back during the full moon. I know I didn't have a perfect focus as I had to use the star minimization method instead of a bahtinov mask but it was really close to perfect. This was with a 400mm lens with a tight crop in post.

ISO 200
F/2.8
1/640s (I think that is what I used)
400mm
K-3

10-07-2019, 11:51 AM   #5
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It is called - chromatic aberrations. It is not a camera, it is the lens. F/4.5 does not work, try F11 or 16.
10-08-2019, 12:37 PM   #6
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f4.5 is a very large aperture, especially for an older zoom lens. You will get more evenly sharp images around f8 - f11. As mentioned before the halo suggests that you slightly missed the focus too.
Was the moon in the centre of the image? In that case you might have a slightly decentered lens, because the top half of the picture looks sharper to me than the bottom half does.
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