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Re: [APML] Optimum focal length for guidescope?
Steve, further to your comment - one thought I was entertaining was a
CLA-7 to attach my ST-7Ei to my 105mm f2.5 lens or maybe my 180mm f2.8
ED lens and to use it as a "guidescope" - very compact! So...I'm very
interested in hearing the answer to your question.
Thanks!
Stuart
Steve wrote:
>Does anyone know why the e-finder/STV combination can
>work well as a guidescope, even though the focal
>length is only in the 100 mm range? This is so short,
>that I'm surprised that it works as well as it does
>for moderate focal length scopes. Is there something
>about the STV itself that compensates for the short
>focal length of the e-finder?
>
>Steve Cannistra
>
>--- Michael Stecker <mstecker@dslextreme.com> wrote:
>
>
>>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)
>>http://www.homestead.com/mstecker/astrogallery.html
>>(Astroimage Index)
>>http://www.homestead.com/mstecker/placesindex.html
>>(Places Index)
>>
>>
>>
>>----- 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
>>>>>
>>>>>_______________________________________________
>>>>>Astro-Photo mailing list
>>>>>Astro-Photo@seds.org
>>>>>http://seds.org/mailman/listinfo/astro-photo
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>>
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>>>
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>
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