Chuck,

In every case, the effect is to increase contrast between features that are otherwise very close in hue and intensity. . . . . The irony is that filters don't really show you more- they show you less, overall.

So, it looks like my understanding about how color filters work is on the right track.

Most of the filters sold to amateurs are probably not needed, . . . The lowest transmission value of every color is essentially worthless.

I can trace my own confusion over planetary filters back to the manufacturers' product inserts and marketing techniques. Like most people, I bought the "basic" planetary filter set first - figuring that these would be the most useful filters. The right information is not uniformly included in the product inserts or on the manufacturers' websites. So the "basic" set turned out to be the least useful. (I seem to recall muttering "worthless" and "stupid" on one cold night. -:) ) I have completed a table assembling descriptions of planetary filter uses from Meade, Orion and Celestron product inserts and websites. If you read the fine print closely, low-transmission level filters (40% transmission or lower) can really only be used with larger apetures - 8 inches or above. Some like a #25 Red (14% transmission) are really meant to be used with 10 inch apetures and above. The "basic" planetary color filter set offered first to amateurs by most manufacturers predominately contain low transmission levels. Typically, these "basic" filters include a 80A Medium Blue (30% transmission), #25 Red (14% transmission), #58 Green (24% transmission). Only #15 Deep Yellow in a basic set has 67% transmission. Looking at Orion's product inserts for illustrative purposes, their "basic" filter set product insert does not mention the limitation of low transmission filters to large apetures. The Orion "advanced" filter set does mention use with "larger scopes" for some low-tranmission filters. Not to single out any one manufacturer, Meade's color filter website and Celestron's product inserts are equally So, I suspect that most people, like myself, buy these filters and then slap them on a 4 or 5 inch refractor - on which they are not designed to work. I tried a range of filters and concluded that "they do not work." Then I went and bought "advanced" "light" color filters that have higher transmissions. E.g. #08 Yellow, Light (83% transmission), #11 Yellow-Green (73% transmission), #82A Blue, light (73% transmission). Then I started getting some useable enhancements in my 5 1/4" refractor. I'd have to write off my own frustration over using color filters properly to bad product insert sheets.

I wouldn't want to part with my light and medium greens and blues, and my yellow-green.

Because of the above, I also found my high-transmission filters more useful, but now that I know how to load up my filter wheel by planet (using my table), I'm going to re-try the use low-transmission filters on larger apeture scopes.

Now, what we haven't discussed is using colored filters to facilitate observation of certain solar features, and I suspect the darker filters may have a new lease on life in that application.

I was aware that a #21 Orange filter could be used to give a white-light solar image an asthetic yellow-sun color, but hadn't thought about the other filters.

Those of you with green lasers can demonstrate this effect. Find a piece of real "day-glow" pink cardboard or plastic, and shine your green laser on it. The resulting dot will be either orange or white. If not, your pink sample hasn't been doped with fluors- it's not true "day-glow".

Neat idea. Your are showing your 60's roots again, Chuck. Wow, man, like look at those colors! -:) - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net