Stars not round

[ChrisIS]

Ok I need to try and sort my stars out, especially the smaller ones are elongated.

I'm using an Atik one 9.0 camera, and both photos were using a tuned EQ6-GT mount.

The Elephant Trunk was taken with a 300mm Canon lens, 1.4 converter, using 20x5min Ha, OIII, SI, a skywatcher 50ED guidescope and SX Lodestar guide camera. This one used KStars Guider.
The cocoon nebula was an 8" Edge HD with a 0.67 reducer at 1340mm with 5min This was using an OAG and Atik GP guide camera 5 min HA & Lum, 3 Min RGB. This one used PHD2.

Frames from different filters seem to have the similar star elongation, Guiding for both seemed to be pretty good. 

Any suggestion for troubleshooting the problem. On the basis I switched most of the kit between the 2 photos, I'm assuming it's either mount to camera related, but where to go from there I'm not sure. 

Thanks in advance

Chris

 

[michael8554]

Could be the lens and converter, or guiding, but the Cocoon image shows all stars elongated the same way, which suggests guiding.

Suggest you show Lights, as stacked images will have averaged out the problems.

Michael