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Escher
Pooh-Bah
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Reged: 08/30/07

Loc: Fenton, MI
CPC1100 with F6.3 FR wont come to focus. new
      #5546416 - 11/29/12 11:02 PM

I'm using the Meade Variable telextender and don't have enough focus travel to bring the image into focus... I've tried setting the extender to its limit and still couldn't bring it to focus.

I feel stupid - I should have posted thi earlier, because I honestly cant remember what limit I was at, long or short, on the extender... I think it was short though, because I have extensions and remember thinking that wouldn't help.

So - What do you do in this circumstance? Is there a different telextender that works with the CPC1100?


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mclewis1
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: CPC1100 with F6.3 FR wont come to focus. new [Re: Escher]
      #5546513 - 11/30/12 12:28 AM

If you have the reducer on the rear cell of the scope (no external focuser or anything like that), then about 50mm of spacers/adapter, then a DSLR you should be just fine. If you have an external focuser or something else that moves the reducer away from the scope you will have more issues with coming to focus.

The Celestron T-Adapter was made for this exact configuration, and with a T-Ring it puts the sensor in a DSLR at about 110mm from the middle of the reducer lens elements (which is the ideal spacing to achieve the full .63x reduction). The Meade unit is similar but has multiple spacers instead the solid body of the Celestron (hence the "variable" part). It shouldn't matter which one you use as long as you have about 50-60mm of spacing behind the reducer and infront of the DSLR (50mm T-adapter, 10mm T-ring, ~45mm depth in the DSLR, and ~5mm to the middle of the lens elements gives you the 110mm spacing).

If you have an appropriate setup (reducer close to the scope and 110mm of spacing back to the sensor) and it doesn't come to focus I would take a very close look at your scope, in particular the primary mirror and see if there is anything intruding into the rear cell (long bolts) that are preventing the mirror from moving through it's full focus travel.


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rmollise
Postmaster
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Reged: 07/06/07

Re: CPC1100 with F6.3 FR wont come to focus. new [Re: mclewis1]
      #5546750 - 11/30/12 07:48 AM

Why are you using the tele-extender AND the r/c? The purpose of the Tele-extender is to produce higher magnification, and it would seem you'd want to run the scope at f/10 in that case...

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Escher
Pooh-Bah
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Reged: 08/30/07

Loc: Fenton, MI
Re: CPC1100 with F6.3 FR wont come to focus. new [Re: rmollise]
      #5546807 - 11/30/12 08:47 AM

Because... im.......not...very.... smart..?

Sorry - noooobie...

/slaps-head

That makes sense though.


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mclewis1
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: CPC1100 with F6.3 FR wont come to focus. [Re: Escher]
      #5547143 - 11/30/12 12:44 PM

Chris, Well you can slap your head ... but I really need to join you. I can't even read properly (Meade variable T-adapter vs. Meade variable Telextender). I'll leave the post above for the info on the spacing requirements ... but it obviously doesn't apply to your problem but might help you setting up the focal reducer.

Major



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