Re: [APML] Raw NGC7000

["Steve Lindsey" <stevelindsey@earthlink.net>]

Thanks Chris.  I'm hoping you're right.  My friend and I have been through a
lot in the past to get pretty good at drift alignment and I'd like to be
solving a different and more straight forward problem for a change.  Like
stopping a lens down a setting! ;-)

Glad you didn't have a problem with the thumb screw but my buddy Dan's ST8 +
colorwheel + 0.8 reducer is pretty beefy and I'm sure a few pounds heavier
than my Nikon body and the 0.8 reducer will be when I shot film with it.
BTW - I'm setting up a modified Lumicon NEG to guide with the ST4 off-axis
like John Boudreau does for film work on the TV85 to avoid the guidescope.

Steve


> Hi Steve -
>
> It looks like the lens is just poor wide open.  I use a separate
guidescope
> in my setup and sometimes need to crank it way off center from the imaging
> scope to find a bright guide star.  I have never had anything less than
> round stars in my images.  Polar alignment does not seen to be an issue
from
> your description.  Try stopping the lens down.
>
> I'll also comment on the single thumb screw on the TV85 focuser drawtube I
> remember someone mentioning.  When I was shooting with TeleVue refractors
> (TV85, TV102 and NP101) all these scope had a single thumb screw design.
I
> had my F3 and .8x R/F attached and never had problems with rotation.  I
> don't know the weight of the ST-8 you are using but it can't be that much
> more......
>
> Best,
>
> Chris
>
> ----------------------------------
> Chris Cook
> Astronomical & Nightscape Photography
> www.abmedia.com/astro
>
> -----Original Message-----
> From: Steve Lindsey <stevelindsey@earthlink.net>
> To: APML <astro-photo@seds.org>
> Date: Sunday, July 06, 2003 5:52 PM
> Subject: [APML] Raw NGC7000
>
>
> >Here's the raw scan (with some levels stretching since the scan was quite
> >dark) so you can tell me what you think caused the arc'd stars around the
> >perimeter.
> >
> >http://home.earthlink.net/%7estevelindsey/NGC7000raw.html
> >
> >My buddy Dan did the polar alignment very carefully on the TV85 with a 3X
> >barlow and 12mm illum. reticle eyepiece.  He worked at this for over an
> hour
> >so I'm surprised if there was field rotation.  We didn't keep good notes
on
> >where the guide star unfortunately.  It was from the off-axis guide chip
in
> >the ST8 Dan was shooting with on the TV85.  His imaging chip was centered
> in
> >the same FOV as this 300mm lens.  Maybe just guiding off-center was the
> >problem but I don't get why this should matter that much if mount was
well
> >aligned and I'm still thinking that maybe the lens doesn't like being
wide
> >open.
> >
> >Let the experts speak...  I'm all ears.
> >
> >Steve
> >
> >
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