Re: [APML] The Veil...

["Chris Cook" <ccjd@ix.netcom.com>]

Hi Don -

I didn't think of field curvature, but at f/5 w/o a field flattener, that
could definitely be it.  I just assumed your were using one  I would pick up
the TeleVue .8x reducer/flattener designed for the Pronto and TV85.  See if
this accessory will improve your images.  The TeleVue .8x R/F is designed to
be used with other refractors besides TV... at least that's what Al and
David say.

Chris

----------------------------------
Chris Cook
Astronomical & Nightscape Photography
www.abmedia.com/astro


-----Original Message-----
From: John Boudreau <jeboud@attbi.com>
To: Discussion of Film Astrophotography <astro-photo@seds.org>
Date: Friday, May 30, 2003 11:54 AM
Subject: Re: [APML] The Veil...


>Hi Don,
>
>As Chuck has said, it certainly looks like the shot is out of focus. The
same for your M8-20 shot posted earlier.
>
>I'm guessing that you're not using a field flattener with the scope--- this
is a 120mm f/5 refractor? If so, it's got strong field curvature. The
"rotated" looking stars would just then be due to off-axis aberrations.
Short of finding a field flattener for it, the best you can do for it is to
knife-edge focus near center, and just use the scope knowing that you'll
have to crop away the outer section of each shot.
>
>BTW--- A dry air or nitrogen purge is still a good idea in damp conditions.
I use a dry air purge based on Herm's system. But I doubt it would have made
a noticable difference in these shots.
>
>John Boudreau
>http://home.attbi.com/~jeboud/astro.htm
>
>----- Original Message -----
>From: "Don Spencer" <ecdon@cox.net>
>To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
>Sent: Friday, May 30, 2003 3:37 AM
>Subject: [APML] The Veil...
>
>
>> Hi All,
>>           I just finished processing my first attempt at shooting the
Veil.
>> http://members.cox.net/ecdon/veil.html
>> You'll notice in this shot that the center seems a bit out of focus, the
>> edges focused real well, but somewhat rotated. This is the second shot
from
>> that night that has this appearance, which leads me to believe that dew
was
>> the culprit(it formed earlier and stayed longer the 2nd night I was out).
By
>> comparison, my M8/M20 photo shows slight curving at the edges and dew was
>> just starting to pick up at the time the photo was shot. I also learned a
>> valuable lesson...it is better to take multiple shots of one area, stack
>> them, and get a quality photo, than it is to spend 2 nights shooting 1
shot
>> of anything in site! I am battling noise in both my Antares region and
>> IC4592 shots.
>> Thanks,
>> Don Spencer
>>
>>
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>
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