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James Cunningham
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Reged: 08/07/10

Loc: Maryland
Keeping focus new
      #6194001 - 11/14/13 06:00 AM

Why do I have to re-focus every time I go out?

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zuben122
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Reged: 07/20/09

Re: Keeping focus new [Re: James Cunningham]
      #6194151 - 11/14/13 09:00 AM

You asked this same question back in June and I don't think the answer has changed. Focus will change as a function of temperature and seeing. With the weather cooling down, if you take the telescope from a 60 degree garage and it's 40 degrees outside, the telescope will actually contract a small but finite amount thereby requiring focus changes. Also, seeing varies night to night and even during the night requiring focus changes as well.

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panhardModerator
It's All Good
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Reged: 01/20/08

Loc: Markham Ontario Canada
Re: Keeping focus new [Re: zuben122]
      #6195149 - 11/14/13 06:18 PM

Re-focusing is such a minor thing why worry about it.

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A. Viegas
scholastic sledgehammer
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Reged: 03/05/12

Loc: New York City/ CT
Re: Keeping focus [Re: panhard]
      #6195164 - 11/14/13 06:26 PM

I use the nifty motofocus with shoestring FCUSB. Makes frequent focusing a snap from indoors and for the CpC and mCX i find that I am constantly tweaking focus as I move around the sky and change filters. Highly recommend it and it's not expensive upgrade either

Al


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HeyJP
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Reged: 12/11/10

Loc: Boulder, CO
Re: Keeping focus new [Re: A. Viegas]
      #6219515 - 11/27/13 02:39 PM

Sometimes it gets cold at night. Sometimes it gets warm during the day. Often they both happen in the same 24 hours. Many parts of your scope expand and contract continuously a temperature changes, all at different rates. And they don't always come back to the exact same spot at the same time the next night.

As you probably have seen, your focus changes throughout the night with temperature change and as you move your telescope to different positions as the weight bearing forces change.

Tweak it every so often and keep looking and shooting.

JP


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rmollise
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Reged: 07/06/07

Re: Keeping focus new [Re: zuben122]
      #6220910 - 11/28/13 08:53 AM

Quote:

You asked this same question back in June and I don't think the answer has changed.




Yep, and conditions are even worse this time of the year than they were the last time you asked. Even a carbon fiber tube will require some refocusing.


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James Cunningham
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Reged: 08/07/10

Loc: Maryland
Re: Keeping focus new [Re: rmollise]
      #6221018 - 11/28/13 10:03 AM

Things change. Also, it is always possible that someone has come up with a viable solution since my last post. Thanks.
Jim


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rmollise
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Reged: 07/06/07

Re: Keeping focus new [Re: James Cunningham]
      #6221264 - 11/28/13 11:53 AM

There's no solution for the expansion/contraction of materials due to temperature change.

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Tel
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Reged: 03/31/06

Loc: Wallingford England
Re: Keeping focus new [Re: James Cunningham]
      #6221395 - 11/28/13 12:53 PM

Quote:

Things change. Also, it is always possible that someone has come up with a viable solution since my last post. Thanks.
Jim




Superficially perhaps, an attorney's final plea in a lost cause, but after almost 3000 posts on CN, I can't help thinking that our Jim's not been attempting to take us for a ride all along .............. or ?


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