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SCT Focuser

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#1 william

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Posted 17 September 2005 - 02:03 PM

I see in some post focuser upgrade mentioned. What are the upgrades that are possible with an SCT focuser :question:

William
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#2 Chris G

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Posted 17 September 2005 - 02:21 PM

I had a WO rotatable crayford that was very nice.

#3 ezrider23

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Posted 17 September 2005 - 02:23 PM

That W.O. crayford and diaganol and $40 gift certificate from Astronomics was tempting. You could use the 40 bucks to buy a nice ep. I sold my sct but still might buy one for my Mak.

#4 garyc11

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Posted 17 September 2005 - 02:28 PM

you can get a dial that fits over the focusing knob i think there 20 bucks at scopestuff or you can get a focuser that goes in front of the diagonal or a focuser diagonal combo. you would rough focus with the standart sct focuser and then fine focus with the focuser upgrade. go to an astro website and look for a sct focuser the william optics combo is around 279 bucks and is a nice unit.

#5 celestial_search

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Posted 17 September 2005 - 05:17 PM

Uncle Rod Mollise did a review of the W.O. SCT Crayford focuser. Check out his website for details. I don't have the line handy but if you type in Rod Molise and SCT you should find his home page.

The ring from scopestuff is what I use. It slips onto the focus knob and is larger so that you can fine tune better. You can still use the stock knob also.

#6 Doug

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Posted 17 September 2005 - 06:47 PM

Starlight Instruments, the best of the best. http://www.starlightinstruments.com/

Doug

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#7 davidpitre

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Posted 17 September 2005 - 07:02 PM

I tried lots of options with my Meade and was happiest with a Borg helical. Less than some of the other options, and the most satisfactory IMO.

#8 Rusty

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Posted 17 September 2005 - 07:24 PM

If you just want to upgrade the stock focusser, a rubber doughnut used for mounting muffers, is about a buck at an auto parts store.

There are focussers that attach to or replace the stock knob, but all use the scope's stock focus mechanism.

Outboard or "add-on" focussers use the stock focusser for rough focus, and take over the fine-focussing duties. The WO Crayford is an excellent value. Others mentioned are a step up in precision, but also a step up in cost.

Electric focussers can attach to the focus knob, or can be outboard focussers. As precision and features increase, so does price.

#9 william

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Posted 17 September 2005 - 07:59 PM

When using the stock SMT focuser, how bad is the image shift? I will be using my C 9.25 for visual use only. If I get the Feathertouch, do I get the one with the most drawtube travel, I am using a GEM mount? The WO package for $279, does look pretty good.

William
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#10 garyc11

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Posted 17 September 2005 - 08:34 PM

i dont have much image shift at all in my c-11. i just bought the ring that goes over the stock focus knob. you may find that you dont need a ad on focuser.

#11 Rat8bug

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Posted 17 September 2005 - 10:21 PM

I see in some post focuser upgrade mentioned. What are the upgrades that are possible with an SCT focuser :question:

William
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Burgess 127/8
CG5ASGT
Celestron 9.25


On my C8, I use the JMI NGF-C. The unit is all aluminum construction and much lighter in weight than the WO design. The unit is mainly used for photography with my DSLR. The purpose is not the typical "focus shift", but to avoid focal length changes when you re-focus. When one focuses by moving the primary to secondary distance, you also change the focal length and thus the image scale. This makes the stacking of images impossible if the images vary in size. I really like this JMI. But it is only for roughing it in. I also use a Borg Helical focuser that is designed for DSLR camera imaging as I describe here:

http://www.barrie-ta.../d70finder.html

Ciao...Barry

#12 Rusty

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Posted 17 September 2005 - 10:59 PM

When using the stock SMT focuser, how bad is the image shift? I will be using my C 9.25 for visual use only. If I get the Feathertouch, do I get the one with the most drawtube travel, I am using a GEM mount? The WO package for $279, does look pretty good.


William
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Burgess 127/8
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Celestron 9.25


If you're only going to be using the scope for visual, I'd go with the WO Crayford, as, IMHO, it's the cheapest decent solution.

#13 matt

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Posted 18 September 2005 - 12:56 AM

If you already have a 2" diagonal, I think you can't beat the Orion helical focuser, it's $44.95
http://www.telescope...ProductID=11734

It's better than a crayford in a sense that as it's helical, it won't suffer from our planets gravitational field when you look towards the zenith. How much do I like mine? I use it for fine focus on my Takahashi! Also, it is said to wobble a bit (no impact on viewing), but it's very smooth, it will hardly shake the telescope.

What I don't like is that it's no-frills: not "security gap" to prevent it from slipping out of its 2" holder (never happened, though), and it's only a set-screw thing.


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