Hi all:
This is my first post.
The day after buying my first dSLR, the Digital Rebel XT (an upgrade over the PowerShot S3 IS), I noticed a spot or smudge, only on skies. After searching through the forums, I believe that it is a speck of dust, but I'm not 100% sure (so I attached an image). it is always in the same place and i only see it on blue sky. I went back to the store, but they are imbeciles, and directed me towards Canon service (which is actually relatively close to where I live) or their own customer service. I still have thirteen days if there is something really wrong or I'm not satisfied with the camera.
So, questions: is it dust? If yes, should I try fixing it myself, or just bring it in to Canon since it is still NEW and under warranty?
Thanks. 

