Jump to content


Photo

CGEM vs CGEM-DX

  • Please log in to reply
26 replies to this topic

#1 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 09:18 AM

I have been trying to find a real major difference between these two and other than weight capacity/tri-pod difference I cannot find much more. I found one site that stated about the DX that "redesigned electronics & constant regulated power to motors capable of driving mount even when not perfectly balanced" I wonder if the CGEM has same deal but just not stated or the DX is redesigned? Also sense a step up from lower level mounts, has anyone found that running near capacity on weight loads (40#/50#) that they really bog down or have diminished tracking ability? I know opinions and likes are varied but just wanting to get an idea... Also am using a C9.25 and am very happy with it and where I live (light pollution) to upgrade too much would be like wearing a white suit to a tomato fight :roflmao: Ps also am using a CG-5 right now that works for video but want something for possible 5+ minute integrations? Also have a CPC tri-pod, can you mount either of these on that tri-pod? thank you
Kasey

#2 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 29 August 2013 - 11:33 AM

DX has a larger tripod, larger counterweight shaft and a motor controller chip that can deliver more current without frying. There is some speculation that all the newer mounts, CGEM and DX, have the newer MC chip. The tripod is a weak link in the CGEM. They still seem to have the same strengths (software) and weaknesses (DEC cogging, 8/3 error).

People say things like I can get 10 minute subs out of my mount but that is not an objective statement. What focal length are you wanting to use and how picky are you?

#3 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 12:57 PM

Hey Mark,
I am right now at about f4/f5 with about 25 lbs. I have the Orion SSAG set-up and have tried on my old CPC but am hoping to do 3+ minute integration without it??? At 30-45 seconds can get good round stars off my CG-5.. I read up some on Yahoo group about cogging,,, is it that visable? kasey

#4 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 29 August 2013 - 01:58 PM

What scope are you using? The DEC cogging will only affect your guiding. Not all mounts have that problem. Mine does not. Mine has a lot of 8/3 error that does not guide well however. For under 1000mm you should be OK if your weight is good. My CGEM with the C11 even at F5 struggles, but this is 1400mm FL.

#5 PhilCo126

PhilCo126

    Gemini

  • -----
  • Posts: 3232
  • Joined: 14 Jan 2005
  • Loc: coastline of Belgium

Posted 29 August 2013 - 02:07 PM

My Celestron CGEM worked flawlessly for 5 years but I upgraded to a CGE because of the Astro-Photography bug :photo:

#6 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 02:36 PM

Hey Mark,
I would use my C9.25, and if ever went bigger would step up in mount as well, (possible DX now as have wifes blessing on this). Unguided about how long can you go with "round stars" with your set-up? I know with where I live (light pollution) and limitations I have on time that it will be a couple years till I could utilize 5 minute subs etc.. I can guide if needed for CCD but would like to be able to set-up, small DVD monitor and Video-view with out a computer. Unguided what length of integrations are you getting, just rough estimate if you can. And Phil I would have to be selling pictures for me to spend that much money on a mount :(,, Thank you Mark, Kasey

#7 orion69

orion69

    Viking 1

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

Posted 29 August 2013 - 04:17 PM

Forget unguided imaging with CGEM or CGEM-DX.

#8 shark-bait

shark-bait

    Viking 1

  • -----
  • Posts: 710
  • Joined: 01 Jun 2009
  • Loc: New Port Richey, FL USA

Posted 29 August 2013 - 04:47 PM

Forget unguided imaging with CGEM or CGEM-DX.

I respectfully disagree Knez. Short subs are not an issue with my DX. Guiding doesn't show a noticeable difference for me simply because of the limitations of imaging in a light polluted area. Of corse that depends on a few variables such as aperature and focal length. Where I live, I can get better quality 60 seconds subs with my 10" f/4 than guiding 300 seconds would yield. Just my opinion.

#9 orion69

orion69

    Viking 1

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

Posted 29 August 2013 - 05:09 PM

It was benevolent suggestion.
On low end mounts unguided imaging is usually unrepeatable and leads to AP frustration.
If you're in a light polluted area imaging with filters would help.

P.S.
Do you know what is man's best invention? :D

#10 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 05:34 PM

Thank you Kenez for the input, and sounds like shark bait and I have the same light issues. I, as am sure he does, use filters, but for me am inclined to view it from his perspective, when dealt lemons, make lemonade... I am not looking to have unguided 5 minute subs, just looking for something that can give fairly good tracking unguided for video A/P. The CG-5 I have is ok for short subs carrying my 9.25, but was purchased as a travel mount. Looking to upgrade now for home (driveway Cul de Sac) heavier mount that can track somewhat reasonably well. I like the ASPA that Celestron utilizes. Do you regret your purchase? Just trying to get a feel on what to expect. Thank you,
Kasey

#11 orion69

orion69

    Viking 1

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

Posted 29 August 2013 - 05:56 PM

My CGEM performance was excellent (even more than that if you know it is after all low-end mount), almost all my images are 30 min subs (with 5" refractor). Even with very heavy 150mm refractor still had no problems with 30 min guided subs which I find very surprising.
Not sure if I'm keeping it yet, must do more testing on targets near equator.
But, it has to be said that according to others, there was issues with some CGEM mounts. I can't comment on that issues because I had none...

Good luck with purchase!

#12 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 29 August 2013 - 06:01 PM

My first CGEM wouldn't do video longer than 20 seconds without elongated stars. It had a pe greater than 180 arcseconds. Celestron did replace it. The point is the CGEM and DX quality is quite variable.

#13 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 06:33 PM

Wow, and I never was a good gambler,,, I can tell you Knez, Mark and most others in here are over my head in A/P. In mechanic terms I would be what is called a shade tree mechanic. I hate to admit it but have no clue about P/E and most other terms. I do know elongated stars tho,, I also know Paramount and A/P are what you would call high end, but for me the CGE and PRO are really high end. The CGEM or CGEM DX are at the end of my price range and should give fairly good results per the price. Do either of you wish you had gone with the DX for possible better results due to load capacity, and possible better tracking? Do you think there is more improvement sense you purchased yours Mark? I do know how frustrating it is to have a flawed mount that tracks intermittently (had a used CPC with clutch problems)... Nothing is easy LOL..
Kasey

#14 shark-bait

shark-bait

    Viking 1

  • -----
  • Posts: 710
  • Joined: 01 Jun 2009
  • Loc: New Port Richey, FL USA

Posted 29 August 2013 - 06:42 PM

On low end mounts unguided imaging is usually unrepeatable and leads to AP frustration.

I can't disagree with this statement. After all the DX IS my high end mount ;). We are playing in different arenas of AP here. I am however content with my results and enjoy the hobby immensely.

P.S.
Do you know what is man's best invention? :D

I do, but it could be considered controversial and somewhat inappropriate.

Regards

#15 A. Viegas

A. Viegas

    Apollo

  • *****
  • Posts: 1044
  • Joined: 05 Mar 2012
  • Loc: New York City/ CT

Posted 29 August 2013 - 08:59 PM

Kasey,

I sold my CG5-AGST and bought a used CGEM for under $1k. I can mount my C8 + C80ED with MCX + SSAG which is close to 25# and can go 3 mins guiding with decent tracking for the Mallincam. With my old CG5 and this scope configuration I was also able to go about 3 mins without a hitch. In both instances I was imaging at about F4 so under 1000mm on the C8. I have now tried using the CGEM with my Istar 150mm which by itself is 27# and with the C80ED mounting on top its over 36#. Again I can go 3 mins without much trouble at about 600-700mm in FL with reduction. I seldom need to go over 3 mins with my mallincam even using Halpha... I think if you are like me then 90% of the time you will be imaging at under 3 mins which honestly means I think you can just keep the CG5 and only upgrade if you come across a good deal for a used CGEM like I did. With the $$ i got for the CG5 my net outlay for the CGEM was like $500 which I think is a fair price to pay... (I also bought my CG5-AGST used, but it was really brand new for under $500)...

Ok... what is the benefit to using the CGEM? Well its if you want to do higher mag imaging. I have used my Mallincam at F10 with the C8/C80ED setup and imaging lets say M57, with the CG5 I had poor results going more than 50 seconds even with PHD. With the CGEM I can go 2-3 mins at F10 without much star bloat or streaking, although I do get some stretched stars near the corners...

So honestly, my advice is to bide your time and upgrade to the CGEM if you find a decent used deal. With all the chatter of Celestron introducing a new intermediate mount (with VX like drive), I think this will drive CGEM prices lower in any event over the next 2-5 months.

Al


P.S. For what its worth I do not think it makes sense to spend close to $2k on the CGEM DX brand new as you can get a much higher quality AP900 used for a bit more or even find CGE Pros on sale or used for just $1k more. The pickup in value from the CG5-AGST with the C9.25 is just not that meaningful with the CGEM DX at full retail.

#16 dragonslayer1

dragonslayer1

    Apollo

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

Posted 29 August 2013 - 10:19 PM

Thank you very much Al, good advice and info.. Have you ever tried the CGEM unguided to see how it does? or was that a mistype on 3 minutes. I right now without SSAG scope & set-up (just using C9.25/telrad/VSS+/adaptors) am using 22# counterweights. Now I did get real good tracking @ 30 sec with that weight and just eye-balling polar align (didn't do ASPA) and target was low on horizion last time out,, I finally had right camera spacing, mounting and things working right... Then weather, work schedule, smoke from fires, etc rained on my parade,, was about a month ago.. But was really pleased with round stars at that weight and set-up, I mean that was a first where everything went and worked right sense I've had the camera,,, fought bad mount, focal distance, proper adaptors etc etc.. Am sure all have been there and rode that buffalo at one time or another.. All the advice and input from all is very much appreciated :bow:,, Thank you
Kasey

#17 A. Viegas

A. Viegas

    Apollo

  • *****
  • Posts: 1044
  • Joined: 05 Mar 2012
  • Loc: New York City/ CT

Posted 30 August 2013 - 06:54 AM

Without guiding and with 25 lbs and at about 900mm I can go a minute without much trouble with ASPA. Again with guiding and below 1000mm FL I think you can get over 5 mins generally...

Oh by the way on teamcelestron.com there is new beta firmware for the CGEM that corrects for the 8/3 and dec cogging and on that board expert users are getting over 10 min guided subs... I am using the latest beta firmware on my CGeM also...

Al

#18 stanislas-jean

stanislas-jean

    Surveyor 1

  • -----
  • Posts: 1991
  • Joined: 22 Oct 2008

Posted 30 August 2013 - 07:00 AM

Don't know if cgem has the same gears but the DX has a 90mm gear diameter.
This is the improvement that I see in combination of more powerfull motor drives.
Stanislas-Jean

#19 Jason B

Jason B

    Proud father of 5!!

  • *****
  • Posts: 6590
  • Joined: 21 Jun 2004
  • Loc: Mid-Michigan

Posted 30 August 2013 - 12:31 PM

Using my regular CGEM, I have not had a single issue. I have shot up to 15 minute subs @ 1600mm without issue. I mostly shoot in the 6 min range lately though as that is the largest part of my dark library....

The key is perfect balance and good polar alignment. I ran the ASPA twice when I first set up. My mount has been sitting on the tripod since (in the observatory). I've changed OTA's multiple times and alignment has held up fine. My imaging set up typically weighs in at around 25 lbs with scope, guidescope, camera, etc.

I have read and heard of all the issues with the CGEM and Celestron's other mount. Our imaging group that hangs out at the Fox Observatory currently have 2 CGEM's, 1 CGEM DX, 1 CGE PRO, 1 AVX and 4 AS-GT's that are routinely used each month. NONE have had any issues what so ever. I know this is a relatively small sample but Celestron has treated out group pretty darn good.

#20 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 30 August 2013 - 01:41 PM

The beta firmware fixes the cogging but not the 8/3 error. The firmware, while very promising, is not problem free yet.

#21 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 30 August 2013 - 01:47 PM

The CGEM has the same gears, as well as same servos, same bearings,and same castings as the DX. It is reported to have the same mc chip now. The differences are the tripod, counterweight shaft, clutch levers, and mc chip.

#22 dragonslayer1

dragonslayer1

    Apollo

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

Posted 31 August 2013 - 09:07 AM

You all are a wealth of information,
I think thru searching the mounts available and companies that back them up, The CGEM and CGEM DX are the best bang for the buck for weight capacity and performance. There are some glitches but for the price, stability and weight capacity I just don't see anything close.. I also realize that wil lnot be doing Hubble grade photos with 15 minute exposures.. It seems that they are trying to address the issues as they can (the beta up-grade),,, will keep watching and listening and LEARNING,, Kasey

#23 DaveJ

DaveJ

    Surveyor 1

  • *****
  • Posts: 1678
  • Joined: 07 Jan 2005
  • Loc: NE Ohio

Posted 31 August 2013 - 01:15 PM

...The CGEM and CGEM DX are the best bang for the buck for weight capacity and performance...


I have to agree. I recently posted this image to the Binoviewer forum, but it's appropriate here, as well.
There's over 50lbs of gear atop my CGEM DX and it doesn't appear to even realize it's there. Tracking is quite smooth.
Posted Image

#24 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15357
  • Joined: 06 Jul 2007

Posted 31 August 2013 - 01:55 PM

The CGEM has the same gears, as well as same servos, same bearings,and same castings as the DX. It is reported to have the same mc chip now. The differences are the tripod, counterweight shaft, clutch levers, and mc chip.


What do you mean by "mc chip" and who told you that? Motor control board, firmware, or what?

#25 Stew57

Stew57

    Mercury-Atlas

  • *****
  • Posts: 2522
  • Joined: 03 May 2009
  • Loc: Silsbee Texas

Posted 31 August 2013 - 04:04 PM

I asked someone at celestron about the control board. They said they were planning on putting the same control chip on both boards as the old chip would be discontined when supplies ran out. He also said that he would not be suprised if the boards ended up the same eventually. He stated the purpose of the updated chip was to allow the servo to pull more current without chip burnout.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics