Jump to content


Photo

New VX or good used CGEM

  • Please log in to reply
34 replies to this topic

#1 starbob1

starbob1

    Apollo

  • -----
  • Posts: 1079
  • Joined: 11 Mar 2007
  • Loc: IN

Posted 14 April 2013 - 07:43 AM

Looking for a mount to pier mount. Had a CGEM before' did fine with guiding for imaging and great for visual. Mostly with a Small Apo on it. But I need a new mount and the VX look like a neat mount at a great price. But pier mounting it could be a problem. One can get a CGEM pier adapter but no VX on the market. Can get a almost new cgem for $1100 or a brand new VX for $800 .Any ideas. Thanks

#2 dickbill

dickbill

    Viking 1

  • -----
  • Posts: 926
  • Joined: 30 Sep 2008

Posted 14 April 2013 - 08:45 AM

I have a feeling that not so many people are going to suport the cgem option, but i'd say it's a good option.
I got one issue once that i could resolve and the 'cogging' problem is not prominent most of the time.
However, a used cgem for $1100 is not a terrible deal, in my opinion.

#3 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2525
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 14 April 2013 - 08:59 AM

If the VX motors and control board ever become available for the cgem it will become a game changer. As of now it is a bit of a toss up.

#4 zawijava

zawijava

    Viking 1

  • *****
  • Posts: 920
  • Joined: 06 Oct 2007
  • Loc: Wells, Maine 04090

Posted 14 April 2013 - 09:53 AM

I don't see the lack of a commercially available pier adapter for the AVX as much of a problem. If you have a pier already I'm willing to bet if you posted pics of it here you'd get enough suggestions that you could get something made locally. I would think the AVX on a pier would be a great choice. I adapted my AVX to sit on my A-P Wood tripod and it's really quite stable. I plan on pier mounting [another] AVX eventually in a small observatory. So show us what you've got to work with :smash:

-Tim

Looking for a mount to pier mount. Had a CGEM before' did fine with guiding for imaging and great for visual. Mostly with a Small Apo on it. But I need a new mount and the VX look like a neat mount at a great price. But pier mounting it could be a problem. One can get a CGEM pier adapter but no VX on the market. Can get a almost new cgem for $1100 or a brand new VX for $800 .Any ideas. Thanks



#5 starbob1

starbob1

    Apollo

  • -----
  • Posts: 1079
  • Joined: 11 Mar 2007
  • Loc: IN

Posted 14 April 2013 - 10:44 AM

Yes Tim I agree' a pier adapter can be made somehow.
I really do not want another cgem'even though a good mount' many issue's can pop up. Plus I bet you the cgem will be discontinued and upgraded like the VX. The price of the VX is great. Reviews look good. I will only use a small refrator or 8in Edge at most so weight will not be a issue ' I already have a 12.5 dob in my observatory and that works great on DSO and planets. My pier uses two top plates of steel 10in by 10in. I already have one plate with the Vixen hub for a GP-D2 and another drilled for a CGE adapter and CGEM adapter from Starzonia. Will post some pier pics later. Thanks all Bob

#6 Dwight56

Dwight56

    Vostok 1

  • -----
  • Posts: 136
  • Joined: 17 Apr 2010

Posted 14 April 2013 - 10:48 AM

Out of curiosity what are the dimensions of the RA and DEc gears on the VX mount I cannot seem to fine that info

#7 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 2544
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 15 April 2013 - 09:43 AM

It sounds as if you have made up your mind against the CGEM, however, if you are pier mounting, I don't know why you would not go with the larger mount with greater capacity and a proven track record. I would only choose the VX if portability was an issue.

#8 starbob1

starbob1

    Apollo

  • -----
  • Posts: 1079
  • Joined: 11 Mar 2007
  • Loc: IN

Posted 15 April 2013 - 01:53 PM

Hi Ed' Your opion is highly valued. Your right why limit myself in the future. I really kind of want a Vixen GP-D2.Even though non goto it was a great mount. 3 min unguided were common. Just have to decide. Thanks Bob

#9 faltered

faltered

    Viking 1

  • -----
  • Posts: 617
  • Joined: 01 Apr 2005

Posted 15 April 2013 - 03:42 PM

The CGEM had some issues out of the gate, but it sure seems that those issues have really subsided. Being a used one, and if you trust the seller - I would have no problem with the CGEM. And I would have total confidence in a new one. The CGEM is a great mount.

#10 ur7x

ur7x

    Viking 1

  • -----
  • Posts: 557
  • Joined: 08 Jan 2012

Posted 15 April 2013 - 07:49 PM

Love both mounts, I would take the CGEM in a heart beat... But it is a heavy beast and not all that portable.

#11 Patrick

Patrick

    Voyager 1

  • *****
  • Posts: 11280
  • Joined: 15 May 2003
  • Loc: Franklin, Ohio

Posted 15 April 2013 - 10:22 PM

ad a CGEM before' did fine with guiding for imaging and great for visual. Mostly with a Small Apo on it. But I need a new mount and the VX look like a neat mount at a great price. But pier mounting it could be a problem. One can get a CGEM pier adapter but no VX on the market. Can get a almost new cgem for $1100 or a brand new VX for $800 .Any ideas. Thanks



I think it really depends on how much weight you want to put on it. I've only seen the VX mount during the day and have never used one. However, I can tell you there is a substantial difference in the size when you look at one sitting next to a CGEM (the VX almost looks puny). But having owned several CG5's I can respect the VX's capabilities. Just make sure you size your instruments accordingly.

Patrick

#12 cn register 5

cn register 5

    Viking 1

  • -----
  • Posts: 760
  • Joined: 26 Dec 2012

Posted 16 April 2013 - 02:18 AM

One point in favour of the AVX is that it has new motors, gearboxes and firmware that removes the non periodic error, and Dec cogging.

There's rumours that the CGEM will get these (possibly as an upgrade but no promises) but at the moment you may get better guiding and definitely better unguided PEC corrected tracking from the AVX. As long as you don't overload it.

Chris

#13 RTLR 12

RTLR 12

    Aurora

  • *****
  • Posts: 4502
  • Joined: 04 Dec 2008
  • Loc: The Great Pacific NorthWest

Posted 16 April 2013 - 10:45 AM

The firmware fix for motor cogging on the CGEM is in beta testing now. The reason this fix has taken so long is because it was not a wide spread problem and therefore was not a priority with Celestron.

Stan

#14 Patrick

Patrick

    Voyager 1

  • *****
  • Posts: 11280
  • Joined: 15 May 2003
  • Loc: Franklin, Ohio

Posted 16 April 2013 - 01:13 PM

The firmware fix for motor cogging on the CGEM is in beta testing now.



Good to know. :smirk:

The reason this fix has taken so long is because it was not a wide spread problem and therefore was not a priority with Celestron.



The way you hear it here on the forums, all CGEM's have been rendered as useless piles of junk due to this 'cogging' issue. :foreheadslap:

Patrick

#15 starbob1

starbob1

    Apollo

  • -----
  • Posts: 1079
  • Joined: 11 Mar 2007
  • Loc: IN

Posted 16 April 2013 - 02:13 PM

I might try one of the new ioptron Q45 mounts instead of the CGEM again. Seems it would be easy to pier mount also.Bob

#16 dragonslayer1

dragonslayer1

    Apollo

  • -----
  • Posts: 1017
  • Joined: 25 Feb 2012
  • Loc: SLC, UT

Posted 16 April 2013 - 09:00 PM

If I recall correctly the payload for VX 30lbs, CG-5 35lbs, CGEM-DX 50lbs, and CGEM 40lbs. The VX is the least of all for carrying capacity from my understanding. Kasey

#17 Mike X.

Mike X.

    Viking 1

  • -----
  • Posts: 799
  • Joined: 28 Jun 2010
  • Loc: Greece-Athens and Rome-Italy

Posted 16 April 2013 - 10:02 PM

Yes those are the stated payloads.
I find the CG5-GT payload of 35lbs unrealistic for astrophotography,which is what our friend wishes to do. Probably the VX may handle a little better the load than the CG5 due to the upgraded base that supports it but..again i have my doubts regarding AP if it is rated fot 35 lbs.
Personally i find the 25lbs a serious higher limit for the CG5 for guided AP, up to 1 meter. Best if under that. ;)

Can't say anything about the CGEM and the DX, i never used them.

#18 orlyandico

orlyandico

    Fly Me to the Moon

  • *****
  • Posts: 5296
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 17 April 2013 - 01:24 AM

IMHO the cogging is not the worst issue. My CGEM has a really bad 8/3 that makes guiding it a challenge. I can get no better than 2" RMS periodic error (as reported by PHD) when guiding with 1-2 second exposures.

Needless to say, unguided imaging is out.

I have also seen the cogging and I imagine it is an issue because the DEC doesn't respond to corrections until they are way too large. But you can avoid DEC guiding by doing a very accurate polar alignment. And, there is a firmware fix available.

For the sole reason that you might get a CGEM with a large 8/3 like mine, I would go with the AVX.

Or wait for Celestron to release an updated CGEM with the AVX motors in it (that should eliminate the 8/3).

#19 cn register 5

cn register 5

    Viking 1

  • -----
  • Posts: 760
  • Joined: 26 Dec 2012

Posted 17 April 2013 - 01:42 AM

Looking at the CG-5 and AVX side by side the AVX looks more capable of carrying a load so I think that Celestron may be being more realistic about the maximum load with it

If it's ever clear I'll try it with the 6" GSO RC with ST80 piggybacked. With the cameras filterwheel and focuser that must be getting close to the limit.

Chris

#20 stevecoe

stevecoe

    "Astronomical Tourist"

  • *****
  • Posts: 4231
  • Joined: 24 Apr 2004
  • Loc: Arizona, USA

Posted 17 April 2013 - 04:11 AM

Orly;

What is the "8/3"??

Steve Coe

#21 orion69

orion69

    Viking 1

  • -----
  • Posts: 989
  • Joined: 09 May 2010
  • Loc: Croatia

Posted 17 April 2013 - 04:22 AM

Frankly, I would really love to test CGEM with cogging and "8/3" problem to compare results with my CGEM.

#22 RTLR 12

RTLR 12

    Aurora

  • *****
  • Posts: 4502
  • Joined: 04 Dec 2008
  • Loc: The Great Pacific NorthWest

Posted 17 April 2013 - 04:30 AM

Have you tried guiding with a different program besides PHD?

Stan

#23 MartinTreadgold

MartinTreadgold

    Vostok 1

  • -----
  • Posts: 110
  • Joined: 17 Apr 2013
  • Loc: Netherlands

Posted 17 April 2013 - 06:59 AM

I just bought the new Celestron Advanced VX mount, and i took it on a weekend trip to Germany, and it was brilliant. The price is very reasonable, 750 Euros here. It's really easy to set up without any fuss. Its a big improvement on the CG-5 mount, and works equally as well as the CGEM mount. As the CGEM mount is bigger, it can handle more weight. The CGEM mount handles upto 40lbs whereas the AVX mount is 30lbs, so weight is the only thing you have to consider here. If you don't plan to use more than 30lbs, go for the VX mount, its newer with more up to date hardware.

See the photo attached of it nicely set up with a 5" Nexstar SCT

Attached Files



#24 FoxTrot

FoxTrot

    Messenger

  • -----
  • Posts: 416
  • Joined: 01 Jun 2006
  • Loc: Melbourne, Australia

Posted 17 April 2013 - 07:59 AM

Steve, I think it has something to do with the 'integer gear' ratios designed into the VX drive, compared to the odd ratio (8/3) in the CGEM. An odd 'non-integer' ratio makes the drive more susceptible to periodic error I believe ? Fox

#25 FoxTrot

FoxTrot

    Messenger

  • -----
  • Posts: 416
  • Joined: 01 Jun 2006
  • Loc: Melbourne, Australia

Posted 17 April 2013 - 08:11 AM

I just bought the new Celestron Advanced VX mount, and i took it on a weekend trip to Germany, and it was brilliant. The price is very reasonable, 750 Euros here. It's really easy to set up without any fuss. Its a big improvement on the CG-5 mount, and works equally as well as the CGEM mount. As the CGEM mount is bigger, it can handle more weight. The CGEM mount handles upto 40lbs whereas the AVX mount is 30lbs, so weight is the only thing you have to consider here. If you don't plan to use more than 30lbs, go for the VX mount, its newer with more up to date hardware.

See the photo attached of it nicely set up with a 5" Nexstar SCT

Martin, I have an LXD75 which I think is substandard for my NP127is (about 7.5 kg, or 16 lb or so). Do you think the AVX would be good with the NP127is? Does it really feel that much more substantial and stiffer than the CG-5?

The CGEM and Skywatcher AZ-EQ6 have caught my eye, but both these mounts are a lot heavier than the CG-5/AVX class mounts, and portability is an issue for me. Thanks, Fox






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics