Star halo has hard edge

Ronald Clanton

Adam,

I've attached a link to the XISF file for IC443 that I took last night.  I used my 8" Edge HD with HyperStar attached (F/1.9 and used an Optolong L-Enhance filter.  Just doing a STF stretch you can see a significant halo around the bright star.  I expected a significant halo, but have never had one that had such a hard edge.  The halo is not like that without the filter.

I examined the individual FITS (also in link) and can also see it there.  So that points to something in the optics that is causing this issue.  I'm not sure if there is something I can do about the optics (maybe a downside with this filter?), but are there any techniques I can use pre/post processing to reduce the effect?

https://www.dropbox.com/s/7bcnf8r9hfqn7as/IC443.xisf?dl=0

Thanks,

Ron

BlockHead

This certainly looks like a normal filter-caused halo to me (especially for NB when you are looking a small number of wavelengths- artifacts will indeed be more crisp).

As for techniques... for this kind of halo- not so much. People usually get different  filters. 

This is particularly an issue for very bright stars... That is a naked eye 5th magnitude star!

All bets are off when looking at/near stars this bright.

-the Blockhead