2009
12.17

In mid 2008, I purchased a new CGE to set up as a semi-permanent mount on my backyard pier.  I’ve now had about a year and a half of working with the mount and thought I’d list some things I learned about the mount and note some of my likes, dislikes, experiences, and preferences.  At the outset I’ll say the CGE is a fine solidly built mount and overall I’m pleased with it, but you know, there’s always “more better”.  Please feel free to add your own thoughts about CGE mounts that may help others with a problem or purchase decision.

The basics:

  • The CGE is a well built heavy mount, with good payload capacity.  Celestron lists the capacity at 65 lbs, although you’d want to be less than that for imaging.
  • The mount is heavy, but it breaks down into three main components  (the tripod, the electronics pier, and the equatorial head) and several little pieces (counterweight shaft , weight, cables, screws, knobs, & wrenches).  The head an tripod are roughly 40 lbs each.
  • Check the Celestron website for all the details on the mount and hand control  software features.

A few things I read about, but didn’t really appreciate until I’d owned the mount for a while:

  • I said the mount was heavy.  When I bought the CGE, I had in mind that I normally leave it permanently mounted on my pier, but that I could take it to remote sites without too much trouble.  The reality is that I found the CGE to be too much for me to tear down, pack up, setup, et. al. for a quick trip to a dark sky site.  It can be done, but it’s painful (at least for me).  I ended up buying a more portable mount for using remote.
  • The CGE does not track past the meridian more than a few degrees.  This hasn’t been a big hindrance, but there are times when it would be nice to have a mount that could track about an hour past.

Problems:

  • The tripod of the CGE has a couple weaknesses.  1) The leg extension locking screws have thread inserts that can come loose.  If the problem occurs, it should be pretty easy to fix by installing new thread inserts with new locktight.  2) The leg spreader attachment to the leg brackets can break.  Always inspect every time you set up.
  • This isn’t much of a problem, but the method of adjusting the azimuth is not precise.  It works easily enough, but it is difficult to make smooth small changes.  Some folks have modified the mounts to attach an adjustment mechanism, others have made special tools with long handles to provide leverage to allow smoother adjustment.
  • Although I have not had trouble with this, there has been a lot of discussion about the RA and DEC cables and their somewhat feeble connection to the equatorial head.   Note that if you have to replace these cables, they are shielded cat 5 cables, and the shield is used as part of the circuit.  Do some research in the Yahoo and Cloudy Nights forums to find suggested sources of good ones.    You can find lots of discussion on the cables and even kits to modify the connections.
  • The servo motor gears.  With  my specific mount the RA servomotor was not smooth enough to allow good guiding.  The vibration of the servomotor was easily seen in the guide logs.  If your guide log graphs look something like the readings below (these are from my mount before and after doing modifications),  and if you’re seeing some elongation in your images, you may want to investigate further.   You can find information about it in the CGE Yahoo news groups.  I’ve posted my experiences with it, and Mike Dodd has written a instruction sheet on how to change the gears in the servomotor to improve the performance.  If you’d like more detailed information about my experience with it, just drop an email or leave a comment and I’ll try to answer any questions.  (Note: I made up a spreadsheet showing the servomotor gear ratios, motor and worm speed, etc.  If you’re interested it can be downloaded here: CGE Ratios Excel Sheet)

CGE_Track_Compare

A couple last notes:

  • Mounting on a Pier:  It is pretty easy to mount a CGE on a pier.  The pier adaptor is a piece that fits into the bottom of the electronics can be purchased or can be easily made.  I ended up buying an adaptor from Durango Skies, but the part is apparently no longer available.  This adaptor I got was/is actually the same piece (replacement part I guess) as the plate that fits into the top of the electronics pier.  Of course this adaptor fits the electronics pier perfectly, and it has a large diameter (about 1″) hole in the center, so fastening it firmly to the base pier is a snap.  If you make your own, the dimensions of an adaptor that will fit inside the pier are:  5.5″ diameter round by 1″ thick plate.  Three 3/8-16 UNC by 1″ deep holes are drilled and tapped on the circumference for the electronics pier attachment bolts.  The holes are equally spaced (120 deg) on the circumference and in the center of the 1″ plate thickness.   The method of fastening the plate to your pier would be at your discretion.
  • I bought the Polar Alignment Scope when I bought my mount.  On the CGE, the PAS is typically not left on all the time, as it may interfere with the DEC cable.  It has a single screw and a recessed seat to help it sit in exactly the same spot each time.  I was pleasantly surprised how well the PAS works and how repeatable it is at each assembly.   Using the PAS during the mount set up and one iteration of the “All Star” polar alignment routine should get you an alignment easily good enough for long exposure, guided astrophotography.
  • I bought a set of knobs from ADM to replace the 3/8″x16 screws that attach the electronics pier and the altitude locking screws.  I didn’t really like the knobs in the upper pier attachment positions.  They stick out enough that it’s really easy to catch cables and whatnot.  The altitude locking ones are great, and I still use the knobs on the lower pier attachment points, but not the upper ones.  YMMV.
  • In working with auto guiding for this and other mounts, I’ve built some optocoupler circuits to ensure there will be no ground loops through the autoguide port.  In doing searches to be sure I understood what the CGE A/G circuits were, I came across a set of schematics for the mount in the Files section of the Yahoo CGE news group.  A fellow had made up the schematics from analyzing his own mount (he also posts an appropriate disclaimer).  I’m noting these schematics here simply because I found them useful on a couple of occasions and others may too.

Please comment if you see errors here or if you have additions that should be made to this post.  I’ve probably missed some important points and will add to this post in the future as needed.

al

9 comments so far

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  1. great post! nice job

  2. Useful post, thanks. The cables are a major weakness of the CGE. Mine malfunctioned over a period of time and eventually I took drastic action and bought the Gary Bennett mod, which uses screw in cables. The socket and wires on the original mount are simply not up to the job.

  3. Thanks for pointing out the issue with the RA & DEC cables. I’ve read several posts in the Yahoo forums where CGE users have benefited from changing to the “Gary Bennett” design/connectors.

    Personally, I haven’t found the need to make the change. I’ve had only one issue in my years with the mount… which was instantly cured by simply reinserting the cable.

    In the future I may make the mods to my CGE. The improved cables & connectors can only make the mount more robust and reliable.

    al

  4. Very useful post and indeed there’re a lot of happy CGE users once they modified their CGE
    Changing the original cables on a CGE mount is a must if You plan on using it a few years longer. Don’t forget that Celestron discontinued the CGE and doesn’t offer technical assistance in Europe for this mount, capable of carrying 30 kilograms (visual use) or 15 kilograms (Astro-Photography).
    Overall the CGE is a robust mount but about the maximum a single user user can easily setup, so a CGE Pro is really a mount for a fixed observatory!

  5. Hey Al, would you kindly send me the link for modifying the CGE gears? Thanks

  6. You can find Mike Dodds write-up in the “CGE Uncensored” Yahoo News group under Files.

    The entry is this title:
    Celestron CGE Mount PEC Improvement.pdf
    Periodic Error Improvement (reduction gears)
    638 KB doddm2001 May 26,.

    I actually had to order a complete motor with gearset and then swap out the gears. However Mike Dodd’s instructions were the instructions I followed. Sorry i don’t still have the order/receipt info for what I ordered so I can’t give you the exact info on what and where to order parts.

  7. Hi,
    After going through several different styles of cat-6 cables on my CGE, I just melted a little solder on the metal shield of each connector of my cat-6 cables so they fit snugly and get great contact of the cables shield to the mount and that fixed the poor ground problems of my RA and DEC cables. I have been using them for over a year now without ever having another problem.

  8. Anyone know where I can pick up a Cge electronics pier…or workaround?
    Thanks,
    Eric

  9. Eric,
    Sorry, I have no clue.

    I’d suggest you post your question on the Yahoo usergroup “CGE-Telescopes UNCENSORED”, or put up a Wanted ad in the Cloudy Nights classifieds.

    Good luck,
    al