Red Halo's using Hutech IDAS LPS P2 MFA filter......

[stan26]

Hello Guys, i'm not sure what to do here. I have just purchased the above a Hutech IDAS MFA kit from FLO (which I may add was a fantastic experience, ordered 1pm friday, arrived on my doorstep 10AM Saturday!!) great service guys! 

However, after doing some trial runs last night using my modded  Canon 1100D, and Canon 200L f2.8 prime and I think I have discovered a potential drawback of using such rear mounted interference filters......  "red halo's" around bright stars. 

I have seen a few topics on the net covering this issue and it seems to be mostly related to camera lenses and rear mounted filters such as this one and the astronomik clip in's..?? which is typical because lenses are all I use these days!

I now need to make the decision of whether I can live with it or not and put up with dealing with them in post processing. Has anyone else experience these halo's using camera lenses/rear filters but have seen them disappear when using the same camera/filter setup on an APO refractor..?

I'm 100% convinced its to do with the fact the filter is mounted at the rear because I once used a Hutech IDAS p2 "front mounted" on this SAME lens with a modded 450D and didn't have any red halo issues at all, and I have plenty of subs in the Iris nebula region sitting on my hard drive to prove this.

So my guess is - (front mounted version filter) the light channels are filtered first and then the light channels are focused by the optics to point X "vs" rear mounted version where the optics focus the light channels at point X first and THEN it is filtered = two different results.

Or could it be the reflection of a certain wave length bouncing off the filter onto the lens optics...?

One good this about the filtered stars are they are noticeably smaller/tighter, I guess this is the filters IR/UV blocking characteristics along with the fact it interferes with the broadband light source.

Other than this, it does a pretty good job of controlling the sky glow

hmm....

( the blue'er images below are 5min subs without the filter, the reddish images are exactly the same setup/conditions using the filter. The comparison image I have overlaid both images at 50% opacity and offset one to aside so a quick easy comparison of the stars can be seen. You'll notice how the pinkish halo stars are smaller)