File This Under....

...If he had brains, he would be dangerous.
The other night, I set up the equipment to image M45 with DSLR and lens.  I got almost two hours of data and when I checked the images yesterday, I noticed horrible purple fringing around the main stars and bloating as well as some distortion.  The lens is a Sigma 85mm f/1.8 operating at f/2.8 and I could not understand how so many things looked wrong.
Sitting down this afternoon a notion came to mind, when I bought the lens, there was a UV filter attached.  Checking the lens, sure enough, the filter was still in place.  The filter clearly distorted the incoming light to add unwanted artifacts. 
I guess it is a case of love and learn.

Paul
​​​​

It has happened us all, silly thing like forgetting to take a lens cap off