Re: [APML] Optimum focal length for guidescope?

["Michael Stecker" <mstecker@dslextreme.com>]

Hello Stuart:

When I was manually guiding back in "those bad old days", I found that if I
used a guiding eyepiece (equivalent) of approximately 6 mm at a focal length
equal to that of the photographing telescope, then I would get good guiding.
Richard Schwartz once told me that you could get good guiding with the ST-4
with a guide scope of 1/2 the focal length of the one used for the photo.  I
routinely guided my 1085 mm focal length telescope with an ST-4 on a guide
scope of 900 mm.


Michael Stecker
mstecker@dslextreme.com

My Web Site:
http://www.homestead.com/mstecker/index.html (INDEX)
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----- Original Message ----- 
From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Sunday, July 27, 2003 11:41 AM
Subject: Re: [APML] Optimum focal length for guidescope?


> Chris, that is very helpful. With my ST-7 then I can go anywhere over
> 800mm for guiding the anticipated purchase. When guiding manually, I'll
> use my apo barlow and be able to guide at double that. Looks like I'm
> fine using the 1000mm achromat to guide the 800mm scope. Manually and
> with a barlow, that scope would give me 167x but the most I'd be guiding
> manually would be a 180mm lens.
>
> Stuart
>
> Chris Cook wrote:
>
> >Stuart -
> >
> >If you're using a ST-4 you can easily get away with less than a 1:1
guiding
> >ratio.  Currently I'm guiding my FS102 (which is 600mm @ f/6)with a 660mm
> >guidscope (60mm f/11 refractor).  If you are manually guiding, I would
stick
> >with guiding with at least 200x.  Back before autoguiders, guys like Kim
> >Zussman in CA would guide at ~600x if I'm not mistaken.  Granted he was
> >shooting prime focus through a C11 @ f/10.
> >
> >Chris
> >
> >----------------------------------
> >Chris Cook
> >Astronomical & Nightscape Photography
> >www.abmedia.com/astro
> >
> >-----Original Message-----
> >From: Stuart Heggie <stuart.j.heggie@sympatico.ca>
> >To: Discussion of Film Astrophotography <astro-photo@seds.org>
> >Date: Sunday, July 27, 2003 1:02 PM
> >Subject: [APML] Optimum focal length for guidescope?
> >
> >
> >
> >
> >>Okay - since it is quiet (and raining) I'll pose a question.
> >>
> >>As I look over my setup - I'm guiding a 400mm apo lens with a 1200mm
> >>guidescope. Seems odd to have 3x the focal length on the guidescope but
> >>seems to work. I may downsize the guidescope to fund the purchase of a
> >>new telescope. If the 400mm apo lens stays in the stable and I buy an
> >>800mm fl imaging scope - what would be an ideal focal length for a
> >>guidescope for both (i.e. for the 800mm Vixen R200SS - 8" f/4
> >>Newtonian)? I have a Vixen/Celestron 1000mm 102mm f/9.8 achromat now
> >>which I'm very pleased with and could continue to use.
> >>
> >>Stuart
> >>
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> >>
> >>
> >
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> >
>
>
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