This is a bit off subject but close enough for me:
I have a spot on my Nikon D3100, it is not the lens.
I went into the menu and did the "clean the sensor" option, but it did not help.
It is near the top about 1/3 of the way in from the left, can't miss it on a sky shot like this.

Any ideas?

It seems to be visible in shots that are sky blue. I have shot I did of objects on a withe background and there is no visible blemish. I can't seem to see it any other time.

(I currently doing a bunch of sky/cloud photos, guess that's why I have noticed it now.)

You need to pick up a sensor cleaning swab at a photography store. I've had this on my D600.

That's clearly a dust spot on your sensor, happens a lot to me, especially on my nex-ea50, I always use my arctic butterfly before every shoot to clean the sensor, works very well.

My d800 had numerous spots that appeared after several time lapse sessions. Some Nikons have an issue with oil getting on the sensor and I wasn't able to clean mine with a cleaning kit in fact that made the spots worse. Nikon fixed it at no charge.

Thanks a lot guys, glad it is just dirt. I did some googling on sensor cleaning and I think I'm going to get someone who knows what they're doing to clean it for me. I didn't pay a lot for this camera but I'm not 100% sure of the process - it seems it is possible to screw things up.

Thanks again!