Baader Fringe Killer and Moon 'n Skyglow Filters in Astroview 100

Hello Skywatchers,

Here is my revised equipment review. Please excuse aspects of any
reposting as I believe the first one sent out was lost in cyberspace.

INTRODUCTION

I tried this Baader filter out night of 5-29-04 for the first time
with a newly reacquired "used" Orion 100mm f/6 Astroview OTA. Thank
you Jamey Thompson for your graciousness in selling it back to me
The moon was all I was able to examine, Jupiter had dipped too low
since my having returned late from uptown events of the evening and in
getting things out and ready to observe.

CRANKING THE LONE SCOPE

Was good seeing conditions. Without any filters at all, this little
achromatic scope showed to handle 255x without abnormal effort viewing
a crisp moon image. Amazingly to my eyes there was no color fringe
seen on the lunar limb _at all_ when using a Meade 4.7mm UWA or
Celestron 4mm Omni Plossl. This was certainly somewhat due lowered
image brightness at high powers yet all was still plenty bright and
with blackness of space for useful direct contrast. This factor of
less brightness was not the entire cause in effect for the interesting
result. The fact is this scope seems to have an exceptionally fine
lens. What a pleasant surprise I've seen a few that were certainly
much worse!

This scope appears thankfully reminiscent to my former yet absolutely
optically superb Apogee 127 WideStar that I had reluctantly sold to
friend Don Bledsoe. Sometime pending his approval it would be an
honor to share with you his excellent commentary in review sent to me
regarding his owning that magnificent scope!

FUN MOVING ALONG

Back with the Astroview, there was some lunar color fringing at lower
powers (higher effective image brightness) but less than I remembered
seeing in comparison to when I very briefly owned/used this same scope
before mainly sighting terrestrial targets. That was obviously prior
to my finally wisely collimating it Great lens! Venus here I
come!

BTW, I'm using a Zeiss Mark 5 binoviewer with 1.25x and 1.70x
correctors in the straight through mode on this excellent instrument
currently within my grip.

WHAT ABOUT THEM THAR FILTERS?

Now you're probably baited to hear something about using the Baader
filters, right? Well, without a doubt, the Fringe Killer most
definitely sharpened the crispness and resolution to view lunar detail
over that of integrated light use of the scope. I should actually
directly compare this filter with yellow (and other) filters to better
understand its true worthiness as a product for an achromat. The
slight amount of purple fringing due chromatism of the lens that was
seen prior to implementation was now gone, seemingly vanished away at
any powers.

The light greenish but predominently yellow hue imparted by this
filter was not too distractive to my eyes and as expected became less
noticeable from true color expectation after a short period at the
eyepieces. It seemed not a world much worse for hurt referencing
degree of off-color tint than to using a TeleVue Radian eyepiece used
without filters. At least as I recall things from prior impression of
that eyepiece. The Baader filter does impart a different color tint
as seen "naturally tinted" in that Televue model.

I can't wait to try this Baader filter on Jupiter and terrestrial
targets for further investigations. Let it be soon!

THE CARDS STACKED

Now, adding in stack formation the Baader Moon and Skyglow filter
together as commonly recommended on the internet made for an
interestingly (but not totally unexpected) poor result. It left a
narrow but strong purple fringe on the lunar limb! And most
importantly, the added system glass made the effective image less
sharp when in accurate focus than to the Fringe Killer filter used
alone or without having any filters employed at all.

IN SUMMARY

Although I completely have doubt, having the moon at a lowered
altitude in the sky may have had a small role in the adverse chromatic
results using the filters stacked together. Even though the apparent
color tone of the moon surface was brought back quite close to natural
(still a little toward the blue) this system combination choice is not
recommended at this point by this observer.

For reference I had the 1.25" filters placed at the bottom of the
binoviewer.

Hoping the data is "found" this time out and useful to some of you...

Clear skies!

Pete (in Arkansas)