What is this ??

[halli]

Hi All

Please see attached image of M101 which has just been partially processed in PI (stretched and DBE applied )  after stacking and calibrating in DSS.

Has anyone seen the artifact in the lower corner before ?  

It re-occurs in every image.

Doesn't look like a dust bunny to me. Flats dont seen to be able to get rid of it and I get it with two different scopes so must be the camera.  

I have a Canon 1100D and may be something on the sensor I guess  - but not sure why it eludes flats and the dust bunnies dont !

Any ideas please ?

Thanks

Ian

[RobRob]

Small hairy particle that moved in the time between taking you flat and your light...

[michael.h.f.wilkinson]

^ That sounds like a likely explanation

[halli]

Thanks - certainly looks hair- like !  

Problem is that its been around for a while now and I have taken a number of sets of flats over a period of time so if it moved in after taking a set of  flats the  succeeding  flats should have got rid of it..........  

[RobRob]

Did you switch your automatic sensor cleaning off (you should to avoid this issue)?

[halli]

I dont think I have an automatic sensor cleaning facility on the 1100D - I still do not understand why flats dont get rid of it if its hair on the sensor.

[ollypenrice]

Flats don't work very well for things on the sensor. They cause a total light blockage. I'm not saying that this is the case here, but flats don't work for contamnation on the chip.

The moving hair is one possibility. Another is that what you are seeing is both a light blockage and a reflection from the contaminant.

Olly

[halli]

Ok thanks Olly -  guess I will need to try cleaning it at some point !