Hi Bruce,

I actually have all three of these filters - I got them years apart as they were
introduced, first the MSG, then the Fringe-Killer, then the Semi-APO. The
Semi-APO is almost always mounted in the front of the diagonal in my 102SLT to
reduce chromatic aberration (which it does quite well). The Fringe-Killer had
that role prior to the Semi-APO coming along. Now I mainly only use it when
imaging with my NexImage camera (web cam) due to its infrared, UV and violet
cutoff features. The MSG gets used the least - mainly just to enhance contrast
and detail on Jupiter and then in my NexStar 11 GPS. The sky glow reduction of
the MSG is subtle, especially in a smaller scope like the 102SLT. The main
advantage in your case would be the more natural color the sky glow filtering
effect imparts when coupled with the minus-violet. That same effect occurs with
the MSG and Fringe-Killer stacked or with the Semi-APO alone.

Hope that helps and gives you an idea of some of the options.

Best regards,
Mike Swanson
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
http://www.NexStarSite.com



--- In Baader-Planetarium@yahoogroups.com, "Bruce Huston" <hustonbj@...> wrote:
>
> I have a Celestron NexStar 102SLT (4 inch f/6.5 achromatic). I am considering
getting the Baader Fringe Killer filter to get rid of chromatic aberration.
Since almost all my viewing is in suburban locations with lots of sky glow, I am
considering the Moon and Sky Glow filter as well. Here is my question: what
would be the advantages/disadvantages of getting these two filters, versus
getting the Semi-APO? I realize that the Semi-APO would be slightly cheaper,
but are there other factors I should consider. Any suggestions would be very
much appriciated.
>