Hi Guys,
It is well known (meaning I personally know more than ten imagers
that have had this problem and it is regularly discussed on several
imaging forums) that the blue and green filters cause halos in RGB
images. Many people believe that they are very bad in the AstronDon
filters. They definetly happen with the AstroDons. I don't have
enough data on non-AstroDon filters to do an objective comparison.
It is obviously more prevalent around bright stars and is worse the
more you stretch the image. I have not seen halos with narrow band
filters of any brand.
Thanks, Rick

--- In ap-gto@yahoogroups.com, chris1011@... wrote:

In a message dated 6/21/2007 12:38:25 PM Central Daylight Time,
kgkirkley@... writes:

you say the Baader filter(s?) do
not cause any halos.

I have been testing the Baader filters for the last week under all

kinds of

sky conditions. I do not see any halos around any bright stars. My

H-a images

are very sharp with no reflections or ghost images around any

stars. Maybe I am

mistaken about Astrodon filters (I have not tested them myself,

but go only

on what I have heard from others). I do know that several of my

RGB filters in

my ST10 camera cause multiple reflection ghosts near bright stars.

I don't

know who makes these filters for SBIG, but they are not of the

quality level of

the Baader series. In my STL11K camera I have installed 3 of the

narrow band 2"

Baader filters and the images they produce are super nice. All

Baader filters

have high grade multi-layer coatings on them to insure freedom

from

reflections.

It may also be that the original poster's reflections are coming

from his

cover glass and filter rear surface, something that can't be

avoided unless the

coverglass is coated with a multi-layer.

Rolando


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