Re: [APML] Red filters and the need to focus

[Brian larmay <power_windows4789@yahoo.com>]

Thanks to who all replied on and offlist..

I calibrated the filter tonight and surprisingly, it
works best at the infinity mark while the H-a is good
1 and a half clicks to the right of infinity.

I shot for 50mins tonight and got kicked out by the
police this time on my last orion shot.
I thought I capped it in time but the result is too
dense to even hold up to a bright light.
I can make out the orion neb though and parts of the
horsehead but all the subtleties are doomed...it
pretty much looks just like a black neg.
Full moon didnt help either and this filter is alot
less dark then the H-a

I miss Wisconsins open state forest land for just
being able to pull over in the state park and not
getting bothered.

Im joining the Buffalo astronomical society sometime
next week so hopefully Ill have more resources.

Cherry Springs is only a few hours away too.

Brian

--- "John C. Mirtle" <spampit@shaw.ca> wrote:
> Thanks for the plug Jim and Bill! Brian, it's worth
> doing the test for all
> the reasons mentioned so far. I use 3 different
> filters on my 180mm, they
> all focus in different places. The difference isn't
> much but it does show
> with tech pan! I haven't focused with 2 different
> red filters but there are
> enough variables that you will want to confirm
> before blowing a good night
> on un-focused shots.
> 
> John Mirtle
> Calgary, Ab. Canada
> 
> ----- Original Message ----- 
> From: "Jim Janusz" <jjanusz@dc.rr.com>
> To: "Discussion of Film Astrophotography"
> <astro-photo@seds.org>
> Sent: Wednesday, February 04, 2004 5:10 PM
> Subject: Re: [APML] Red filters and the need to
> focus
> 
> 
> Hey Brian,
> 
> The very best way to calibrate the focus of a red
> filter is the photographic
> method that John Mirtle describes on his web site. 
> Anything else is just
> close.
> 
> http://members.shaw.ca/jmirtle/ha.htm
> 
> Jim
> 
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=====
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