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2" O-III : ugly but cheap For Sale

Price - $35.00

Ad Number: 102350

Posted: 02 Apr 2017

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This O-III filter is ugly, but amazingly still does the job!

I got it from a CN member some five years ago or so. It was described as a Lumicon OIII filter, remounted in a Lumicon Neutral Density ring. It is definitely an OIII, and the ring reads "Lumicon ND25". It probably is an old Lumicon, but I can't actually vouch for that. Or maybe I can.

I know that older Lumicon filters had a coating issue, apparently. Over time, they get ugly, as this one has. The outer zone of the filter, all around, has degraded into the mottling you can detect in the photos. (Note that taking photos of narrow-band filters can yield some weird colors due to interference and diffraction at the surface):
  • The full-photo shows a purplish ring around the perimeter of the filter; this is the most deteriorated area. Ignore the dust and its reflections; the glass has no scratches or pits.
  • The close-up photo shows the reticulation in more detail (weird colors, though, at this angle of illumination!).
How much this issue affects the function of the filter is unknown. For my part, the filter has given me amazing views of nebulae like M42, M8, and M27, not to mention revealing the full beauty of the Veil Nebula.

It was in this condition when I got it, and I felt a bit bamboozled on the purchase, but since it was cheap and worked better than expected, I kept it. Meanwhile, it hasn't gotten worse. The interior of the filter is OK, only beginning to show a problem.

So despite this obvious issue, it still does a pretty decent job. If want a 2" OIII on the cheap, this'll do! Case as seen included.

Please cover shipping and PayPal charges. With the above information, you know it is what it is; I won't do a refund on this item.


  • Condition Ugly
  • Location Colorado

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