Re: [APML] H-A filters

[Nicola <nmontec@libero.it>]

Hi George,

I used a hartmann mask for all my objectives 50,135 and 200 with good 
results. I wanted to make sure that the Anti-UV filtre didn't shift the 
focus appreciably and that's what I found, fortunately. I'm going to try 
  it again on a couple of filters I recently bought (yellow-orange and 
dark red) and I think this time I should notice the difference!

ciao
Nicola

George Anderson wrote:
> I recently picked up a used 77mm Lumicon H-Alpha filter.
> The only problem I have is that the filter seems to be a 72mm with a
> 77mm step up ring screwed on.
> Looking at Lumicon's website I see that the filter is only offered in
> 77mm and not 72mm.
> Is this step up ring normal?
> Also there are no markings on the filter to indicate that it was made by
> Lumicon, just flat black anodizing. Is this normal? But the filter case
> does say Lumicon H-Alpha pass filter.
> 
> Question to John Mirtle
> Can the Hartman mask method for focusing be used on 50mm and 28mm
> lenses?
> 
> OT: Welcome back Rob!
> 
> George Anderson
> Montreal Canada
> 
> Clear skies (not here) and good health
> _______________________________________________
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> Astro-Photo@seds.org
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> 



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