Re: (IAAC) Obj: M57 the "Ring Nebula" - Inst: Orion 6" Dob

> Observer: William L. Schart
> I experimented with various cobinations of EPs, barlow and filter...
> ...
> Although the filter did not make the nebula any easier to see, it did
> increase the amount of detail visible. The "hole" was much more apparent.
This was a surprising contrast effect, William! Normally, one would expect
using the filter will INCREASE the contrast of the inner nebulosity: after
all, those gases are emitting at the same wavelengths as other PNs do!
But the inner nebulosity is naturally much fainter than the outer ring.
And after all, no emission filter has 100% transmittance in its selected
wavelengths: so obviously, although adding the filter would have increased
the CONTRAST (relative brightness) of the inner nebulosity versus the sky
background, I guess it attenuated that nebulosity to much to be seen...
Anyway, thanks for yet another interesting observation!
Take care,
Lew Gramer
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