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[QUOTE=ReaPerMan;1003688]Thanks for the advice Greg. I have noticed some of the problems you mentioned and I have a program called PTLens which is supposed to fix Pincushion and Barrel distortion. it provides a number of adjustments including the centering. I need to experiment with it a bit more as I haven't ventured beyond the default settings yet. It would appear that the old adage of you get what you pay for is in full effect.
Depending on who you bought it from you may find them quite accomodating. I bought mine online and expected some problems as they said you had to return within 2 weeks of ordering. Silly really as they took 6 weeks to deliver it to me. I sent an email saying this and that the images showed bad star elongations on one side and sharp on the other. I sent an example image and they replaced it. It took another 6 weeks but the next lens was good.
The problem you are seeing is not pincushion or mustache distortion. Its coma. Distortion would simply be a wavy type look to the foreground. I am not sure if its even noticeable in a nightscape. I have seen lots of Samyang 14mm F2.8 images and never noticed the distortion. I think nightscapes are very forgiving of that and very hard on coma and chromatic aberrations in the extremities that are often forgiven in terrestial images. What I see on the net about lenses is the elements can be decentred and this causes this type of defect. I guess thats why you pay big bucks for high quality Nikon, Canon and Zeiss lenses.
Greg.
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