From: Milton Aupperle <milton@outcastsoft.com>

Date: March 10, 2008 7:36:09 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Quick Time Invisible

Hi Perry;

On 10-Mar-08, at 6:16 PM, Perry Holcomb wrote:

Milton,

Earlier in this thread you mentioned you use a LPF to

enable longer exposure times without encountering

washing out via light pollution.

It helps a lot, but nothing beats clear dark skies.

What kind do you use? 

I have an Antares ALP and a Hutech IDAS LPS. I only use the Hutech now, as it lets in more of the "good light" than the Antares one does.

http://www.sciencecenter.net/hutech/idas/lps.htm

I ask because I've read that

they essentially do no good!  So, it was refreshing to

hear your comment that you could expose 4X longer

using one.

They can make a difference, however it depends on what the light source that is fogging your skies. If it's broadband light sources then nothing may work.

Check out

http://www.astropix.com/HTML/I_ASTROP/FILTERS.HTM

http://www.astromart.com/articles/article.asp?article_id=250

I found a really great comparison of several filters both for measured transmittance and also actual imaging results last year, but can't find that link again. It was in german, and had actual image comparisons of DSO targets.

HTH..

Milton J. Aupperle