Blue/white artifacting stars

[DJago]

Hello, I'm processing NGC 6188 and I'm having trouble with some misshapen/artifacted/discoloured stars.    The effect is visible after stretch/channel combination (SHO pixelmath).  I was wondering if anyone knew why this happens and how i can prevent it from happening? 

https://imgur.com/cDLcOzQ

https://i.imgur.com/Sh70j2V.jpg

https://i.imgur.com/BH9dMDK.jpg

I'm using a william optics gt81 and an ASI 1600mm-c. 

Thanks.

[wvanreeven]

Did you refocus when switching to the blue filter? I suppose you did.

It may be a blue halo caused by imperfect optics. I had the same problem with my WilliamOptics ZS71 ED.

[DJago]

Did you refocus when switching to the blue filter? I suppose you did.

It may be a blue halo caused by imperfect optics. I had the same problem with my WilliamOptics ZS71 ED.

It may have something to do with using different brand filters.  I'm using a ZWO HA filter and Astronomik Oiii and Sii filters.  Imaging for each channel was done on different nights so focusing isn't the issue.

[wvanreeven]

Ah wait I hadn't seen that you were using small band filters. Then please ignore what I wrote about imperfect optics because that only comes in play with broad band imaging.