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Why is there an artifact in top edge of my picture?
Is this something in my sensor? There are two black dots visible under the shutter artifact, but could some litter cause this kind of "ghost shape"
This artifact falls under the heading of flare / ghost image. It is caused by internal reflections. The camera lens is a complex array of multiple polished glass lens elements. Some elements are cemented together, some are air-spaced. Each has two polished surfaces that reflect away about 2% of the light that otherwise would traverse the lens. The 2% that is reflected hits other polished surfaces and reflects. The bottom line is, there is a fair quantity of unwanted reflections going on inside the camera.
Most of this stray light bathes the film or sensor with a uniform level of stray light, and this reduces image contrast. What you are seeing is a ghost image of the iris (aperture). This is a common phenomenon caused when there is a bright light source just outside the edges of the image.
You could have likely mitigated this artifact if you had mounted a lens hood. This is a funnel-like attachment that mounts surrounding the front of your camera lens. The lens hood shields the lens from seeing bright sources that are just outside the camera’s field of view. You might consider buying one, they are not too expensive. If due to bright light sources within the vista, nothing works to mitigate.
In the past, such artifacts and ghost images were more evil. Glass lenses actually reflect away about 4% however, nowadays they have a coat or multiple coats of minerals that reduce reflections to about 2%.
Nothing to do with your sensor, these are reflections of some bright light on the individual lenses in you lens. My bet is parasite light from the lamp post under which you were when taking the picture (lens hoods are also useful at night).
The dark spots could be birds.
The bright polygon spot in the sky can be a small water droplet on the lens.
Or, more probably, on the filter if you used one - the spot size and shape implies some distance between the optical irregularity that creates the spot and the lens.
The spot has a symmetric interference pattern suggesting that the light source illuminating it is not too much on the side, so the lens hood would probably be of little help.
The dark spots can be created by non-transparent contamination at the same surface, but they are too dim to be sure.
interesting: the "beams" around the lamps (14 around each) and the polygon shape (7 sides) are probably created by the same 7 diaphragm edges. Are the edges in fact 7 in your setup?
I don't think this is flare, though flare can often look similar to this.
This looks more like a drop of moisture, perhaps a single melted snowflake, was on the front of the lens and refracted the bright light from the streetlamps in that way. Out of focus water drops on the front of a lens can often demonstrate the "onion skin" layers in an aperture shape.
Do you mean the 7 sided polygon on the top? That's your aperture blades. What is the origin of the hexagonal artifact of direct sunlight/spotlight photos?
You're catching flare from the light, it is bouncing between lense elements, and eventually exiting in that orientation. You're at a very small f-stop with lot of integration time to pick up subtle flare.
Had you shifted the lense down or up you could probably push it out of the frame, although you may still have had an indistinct lightening / cast in the direction of the flare.
A lense hood may mitigate or eliminate the artifact if the light was outside of the lense FOV but, given the source is the light in your photograph, this artifact still would have shown up.
Edit: htps://www.opticallimits.com/olympus--four-thirds-lens-tests/464-pana_20_17
Number of aperture blades 7 (circular)
