Lumicon sells their seconds (at least the old Lumicon did) at the big, national star parties for a reduced price. They are clearly marked as such, and the transmission specs are marked on the package. Most of the Lumicon filters came with tables listing transmission figures in percent rather than a graph. Brent --- Chuck Hards <chuckhards@yahoo.com> wrote:
Any narrow-bandpass filter should come with a print-out graphing transmission near the selected wavelength. If you can't find one, look under the foam padding in the case, if any. Might also be folded up with the shipping invoice.
Comparing these charts may tell the tale.
Many filters sold second-hand are literally "seconds", meaning they may not meet quality standards for some reason or other, and can't be sold as "new". There could even be a cosmetic flaw that doesn't affect perfomance. Most reputable manufacturers go to great pains to keep such seconds off the market.
Individual filters among the same manufacturer will rarely be absolutely identical, even in the same lot. While all filters should pass certain quality standards, on certain objects there may just be a grain of truth to the concept of a "lemon". Repeat the test on other O-III objects if possible, guys.
C.
--- Richard Tenney <retenney@yahoo.com> wrote:
FYI,
Friday night (or more likely early Saturday) we had a filter showdown in my 16-inch on the Veil nebula; my 2-inch Lumicon O-III vs. Jim Gibson's new 2-inch TeleVue O-III (which by the way costs nearly $30 more). The difference was HUGE. Lumicon beat the pants off the TeleVue. In fact, the TeleVue was so bad you could hardly see a difference between the filter and no filter in terms of contrast with the nebula.
Don't know if Jim just got really unlucky and happened upon a defective filter, but if this was any indication of quality, I'd highly recommend you stick with Lumicon (Jim's going to try for a refund in the meantime!).
For those of you who haven't looked at the Veil through an O-III filter, it's rather dramatic -- one of my very favorite sights in the summer sky. You can spend a lot of time tracing the extensive loop in Cygnus...
Rich
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