Jump to content


Photo

Flexible focus extender

  • Please log in to reply
7 replies to this topic

#1 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 14 October 2012 - 02:58 PM

Does anyone know where to get one of those flexible focuser extension things like Scopetronix used to sell?

I recently got a used 105 with a focus knob that has extreme image shake problems. Would an extender help with that?

#2 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2560
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 14 October 2012 - 06:07 PM

A piece of ruber or plastic tubing will work fine. I have used aquarium hose before.

#3 tomatohead

tomatohead

    Explorer 1

  • -----
  • Posts: 79
  • Joined: 21 Nov 2010

Posted 14 October 2012 - 07:10 PM

Go to an auto parts store and get a speedometer cable cut off a few inches (approx. 8). Get a large knob and make it as light as possible. Drill a hole in the center of your original focus knob to accept the cable. Epoxy the speedo cable to your original focus knob and epoxy the other end to the larger knob.
This worked well on my 125 the larger knob helps a lot in fine focusing.
Making the replacement knob as light as possible will produce produce less stress on the focus exit shaft and plastic exit point at the rear of the scope.
You may want to "sleeve" the focus shaft but that another mission.

#4 blb

blb

    Aurora

  • -----
  • Posts: 4529
  • Joined: 25 Nov 2005
  • Loc: Piedmont NC

Posted 14 October 2012 - 07:21 PM

I recently got a used 105 with a focus knob that has extreme image shake problems. Would an extender help with that?


YES, it helped to greatly reduce vibration in my ETX125. Plus it enabled me to focus when the focus knob was not reachable when looking close to the zenith.

#5 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2560
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 14 October 2012 - 08:17 PM

The meade 1244 would be the best solution. I modified one for my etx80 that I bought for $29 a several months ago.
A short video of focuser in operation in link below. The wiggle at the start and wiggles at the end are the controller being removed and replaced on the velcro attached to the tripod legs.

http://s906.photobuc...erOperation.mp4

#6 astrohep

astrohep

    Lift Off

  • *****
  • Posts: 19
  • Joined: 10 Dec 2004
  • Loc: cypress, tx

Posted 21 October 2012 - 08:25 PM

keep an eye on ebay. i picked one up 2 weeks ago for $7.50 shipped.

#7 mayidunk

mayidunk

    Don't Ask...

  • *****
  • Moderators
  • Posts: 4106
  • Joined: 17 Feb 2010
  • Loc: Betwixt & Between...

Posted 21 October 2012 - 08:28 PM

Here is one being sold on amazon for $9.95 plus S&H.

#8 Hitech

Hitech

    Ranger 4

  • *****
  • Posts: 387
  • Joined: 03 Jun 2010
  • Loc: NW PA.

Posted 01 January 2013 - 01:26 AM

Just be mindful of an extender that has a long collar that slips on the focus shaft since that will limit the scope's pointing at zenith or directly upward. Also make sure the cable or tubing is felxible enough to keep it from binding or wiggling about while focusing. Some cable focusers are too stiff and slightly moves the OTA as you focus.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics