Re: [APML] Exposure with lumicon HA filter

["Stuart Heggie" <stuart.j.heggie@sympatico.ca>]

George, if you mean a narrow band filter I expect you can go as long as you like. If you mean a
camera lens filter that is really a deep red cut-off filter, I suspect 4x is easy but I think Jerry
Lodriguss' CD / Website has info on Deep Sky filter factors which would give you a minimum value
anyway.

Beauty in things exists in the mind that contemplates them.

Stuart
http://www3.sympatico.ca/stuart.j.heggie/Stuart.J.Heggie/
Flesherton, Ontario, Canada

----- Original Message -----
From: "George Anderson" <georgea@cam.org>
To: "APML" <astro-photo@seds.org>
Sent: Saturday, August 07, 2004 1:07 AM
Subject: [APML] Exposure with lumicon HA filter


> I am looking to get a rough idea as to what (if possible) the filter
> factor is for the HA filter on starlight.
> For example if I were to shoot a region (widefield) and be able to
> expose for ten minutes unfiltered before background (light polution) fog
> became a problem, how long would I have to expose with the HA filter to
> capture the same number of stars? This is assuming the same B&W film
> with good spectral response to 656nm.
> I realize that mileage may vary, but I am looking for a ballpark figure
> to quantify some results.
>
> George Anderson
> Montreal Canada
>
> Clear skies and good health
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> Astro-Photo@seds.org
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