50mm f1.8 photos at f11 or higher show spot

After viewing an aircraft shot I took this afternoon I realized how dirty my ccd is, so I cleaned it. went outside with the 50mm and shot the blue sky to check my cleaning job and noted a "fingerprint sized" spot just to the right barely of dead center of the frame. This spot is brighter than the surrounding area, bleached out looking. The edges of it are soft but it is fairly well rounded.

Trying to determine what was causing it, I took a series and found the spot shows up at F11 barely but is obvious at anything higher.. from F1.8 up to F10 I really can't see it. This lens is fairly new.. haven't really used it much other than some test shots, but those weren't something I'd catch this lighter dot on, so here I sit wondering what the heck...

Have any of you ever noted this? Is it a lens defect? ..just the way it is? .. I took shots with my zoom at 50mm and it doesn't do it, so it's definately the lens. I took shots of the sky, the garage door across the street and the clouds in a different direction over the course of about an hour... the dot remains exactly in the same spot, even after cleaning and since it seems related to the aperature.... well that's all I know.

Will really appreciate hearing from anyone with info..
Laryl

 

wow.. learning everyday. thanks much!

 

I use the eclipse/pecpads/swipe Sensor Care Kit that I picked up from Nicholas R site.. he has great instructions that come with it.

http://www.pbase.com/copperhill/ccd_cleaning

Living in the dusty desert I have to clean mine every few months.. those specks just won't go away by blowing them where I come from

 

I'm not happy with the spot but happy to understand what causes it exactly.. bummer tho to buy a nikon lens able to shoot up to f22 and be told to be careful over F10.. sigh.

Laryl