Jump to content


Photo

Extended Polar Shaft for CGEM Is Here!

  • Please log in to reply
15 replies to this topic

#1 Mike Harvey

Mike Harvey

    Apollo

  • -----
  • Posts: 1073
  • Joined: 01 Mar 2004
  • Loc: Orlando, FL.

Posted 15 July 2009 - 01:58 AM

Criterion Machining is now shipping these. They're nearly twice as long as the shaft that comes with the mount! Beautifully done...and I can now balance my setup with LESS THAN HALF the counterweights I needed previously.
The mount is no longer OVER-loaded.
Unfortunately, I haven't been able to see if there is a significant improvement in overall performance, due to weather and work.
As soon as I do, I'll post the result.

Mike Harvey

#2 Luigi

Luigi

    Fly Me to the Moon

  • *****
  • Posts: 5320
  • Joined: 03 Jul 2007
  • Loc: MA

Posted 15 July 2009 - 07:01 AM

Dec shaft?

#3 Deven Matlick

Deven Matlick

    Vendor - Criterion Machine Co. LLC

  • *****
  • Vendors
  • Posts: 174
  • Joined: 31 Dec 2005
  • Loc: Moatsville, WV

Posted 15 July 2009 - 11:31 AM

Counterweight Shaft not Polar Shaft!!

But thanks anyways!!

#4 Peter in Reno

Peter in Reno

    Fly Me to the Moon

  • *****
  • Posts: 5795
  • Joined: 15 Jul 2008
  • Loc: Reno, NV

Posted 15 July 2009 - 01:14 PM

I was told that the longer the shaft the more vibration. In other words, it may be better to increase CW and move it closer to the mount rather than lighter CW and further away from the mount. The further away from the mount increases moment of inertia which is not good. Thicker CW shaft would be nice. You may not notice the vibration with longer CW shaft if you are using visually, but for astrphotos, your CCD may show out of round stars due to vibration.

See this old thread:

http://www.cloudynig...5/o/365/fpart/1

Peter

#5 Mike Harvey

Mike Harvey

    Apollo

  • -----
  • Posts: 1073
  • Joined: 01 Mar 2004
  • Loc: Orlando, FL.

Posted 16 July 2009 - 01:38 AM

Good Info - thanks!

Re: "polar shaft"...that's why I should stop posting in the "wee hours"!!!

Mike :foreheadslap:

#6 JadeSmith

JadeSmith

    Viking 1

  • *****
  • Posts: 779
  • Joined: 15 Jul 2008
  • Loc: SE Michigan

Posted 16 July 2009 - 02:41 PM

Can the CW's from a CG5 be used on the CGEM? Is the shaft the same diameter?

#7 Deven Matlick

Deven Matlick

    Vendor - Criterion Machine Co. LLC

  • *****
  • Vendors
  • Posts: 174
  • Joined: 31 Dec 2005
  • Loc: Moatsville, WV

Posted 16 July 2009 - 04:17 PM

Yes, They are both 20mm diameter shafts and in fact the shafts or weights are interchangeable between the CGEM & CG-5!

#8 Kolenka

Kolenka

    Apollo

  • *****
  • Posts: 1181
  • Joined: 01 Jun 2008
  • Loc: Seattle Area, WA, USA

Posted 17 July 2009 - 02:56 AM

I might have to pick up one of these... I just took shipment of a CGEM and noticed that the RA is inherently unbalanced out of the box (unlike the CGE which balances perfectly without anything on it)... mix that with the short rod and it definitely seems to be ripe for balance frustrations.

EDIT: Of course, it helps if I actually understand I have a 17lb CW, not a 22lb CW...

#9 Lane

Lane

    Soyuz

  • -----
  • Posts: 3586
  • Joined: 19 Nov 2007
  • Loc: Frisco, Texas

Posted 17 July 2009 - 03:34 AM

I still like the design of the Vixen Sphinx best of all. The polar axis goes through the top of the mount, so you if you attach only a small ota you don't even need a counterweight at all and with a bigger scope you only need a tiny counterweight. Good design making the mount itself into a counterweight.

#10 JadeSmith

JadeSmith

    Viking 1

  • *****
  • Posts: 779
  • Joined: 15 Jul 2008
  • Loc: SE Michigan

Posted 17 July 2009 - 10:37 AM

The Vixen mounts seem pretty cool....just a little expensive IMO.

#11 pollux

pollux

    artiste

  • *****
  • Posts: 7330
  • Joined: 01 Apr 2004
  • Loc: Burnaby Canada

Posted 17 July 2009 - 11:29 AM

I like my ex-Sphinx SXD. Major reason is the mechanic design like what Lane has mentioned. 10 pounds counterweight is enough to hold a 23 pounds scopes.

If it wasn't my job loss I wouldn't get rid of it.

#12 Deven Matlick

Deven Matlick

    Vendor - Criterion Machine Co. LLC

  • *****
  • Vendors
  • Posts: 174
  • Joined: 31 Dec 2005
  • Loc: Moatsville, WV

Posted 23 July 2009 - 01:12 PM

I might have to pick up one of these... I just took shipment of a CGEM and noticed that the RA is inherently unbalanced out of the box (unlike the CGE which balances perfectly without anything on it)... mix that with the short rod and it definitely seems to be ripe for balance frustrations.


Well just let us know if you have any trouble and end up needing to get the shaft. :lol:

#13 Kolenka

Kolenka

    Apollo

  • *****
  • Posts: 1181
  • Joined: 01 Jun 2008
  • Loc: Seattle Area, WA, USA

Posted 23 July 2009 - 05:39 PM

I will, but as I mentioned in the edit, it'd help if I knew how much weight I actually had on the mount compared to the gear.

I had 28lbs of CW fairly far in the rod holding 22lbs of gear, not the 33lbs of CW like I thought. That is a pretty big difference, and also explains why the CW couldn't hold my 30lbs of gear in place even at the end of the rod.

#14 Deven Matlick

Deven Matlick

    Vendor - Criterion Machine Co. LLC

  • *****
  • Vendors
  • Posts: 174
  • Joined: 31 Dec 2005
  • Loc: Moatsville, WV

Posted 23 July 2009 - 07:47 PM

I will, but as I mentioned in the edit, it'd help if I knew how much weight I actually had on the mount compared to the gear.

I had 28lbs of CW fairly far in the rod holding 22lbs of gear, not the 33lbs of CW like I thought. That is a pretty big difference, and also explains why the CW couldn't hold my 30lbs of gear in place even at the end of the rod.


What kind of setup were you trying to use on the CGEM and could you post a picture?

#15 waassaabee

waassaabee

    Fly Me to the Moon

  • *****
  • Posts: 5116
  • Joined: 26 Nov 2007
  • Loc: Central California Coast

Posted 23 July 2009 - 07:59 PM

None of this sounds like my CGEM. Granted I'm only sporting about 17lbs of gear, but my single stock cw is about halfway up the stock shaft. And for damping purposes I'm considering Casady cw's... maybe 3 of lighter weight, smaller diameter/taller height to spread along the bar. Seems it you hang a stack of weight farther out, it's going to want to go harmonic on you.

#16 Deven Matlick

Deven Matlick

    Vendor - Criterion Machine Co. LLC

  • *****
  • Vendors
  • Posts: 174
  • Joined: 31 Dec 2005
  • Loc: Moatsville, WV

Posted 27 July 2009 - 03:43 PM

Unfortunately, I haven't been able to see if there is a significant improvement in overall performance, due to weather and work. As soon as I do, I'll post the result.

Mike Harvey


Mike,

Have you had a chance to put the new shaft through it's paces?? !@#$%






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics