Strange Artifacts

[gnomus]

I was shooting some test shots through the C8 Edge yesterday whilst checking that my new focuser was working.  

These were daylight shots, through a window at a distant electric pylon.  The image was covered in strange artifacts.  At first I thought they were semi-circles, but on closer inspection they appear to be full circles with one half darker than the other. 

The artifacts remained 'locked' in position on the same part of the screen if I jiggled the scope or rotated the camera in the image train.  This seemed to me to rule out the possibility that these were objects on the window, or the scope.  It seemed to me that it must indicate something in the camera.  I inspected the sensor, but could see nothing obvious.  I used a bulb blower but the artifacts seemed to be still there and in the same place.

I've not seen anything like this in my lunar or planetary images.

Apologies for the resulting image - it is a screenshot of one frame from the image (all attempts to 'stack' produced very strange results).  I've circled some, but not all, of the artifacts.

Any thoughts?

[michael.h.f.wilkinson]

Out-of-focus objects like dust in the optical path can produce these donut shapes. The odd shape is due to the annular shape of the aperture.

[halli]

Hi there

Yes strongly suspect this is dust on the camera sensor - see the following thread  

http://stargazerslounge.com/topic/233289-dust-i-asssume/

Flats will eradicate these although a bit of a pain as I wait until the following day to take them !  

Cheers