Click here for a new source of CG-5 replacement parts!
These web pages describe and illustrate how I improved my CG-5 German Equatorial Mount. I did this by disassembling its equatorial head; removing the existing grease; cleaning, smoothing, and polishing internal bearing surfaces; regreasing with a good-quality synthetic grease; and carefully adjusting the worm and other components.
The project required about nine hours to complete, and the final results are well worth the effort. I can now turn the RA and Dec worm shafts with my thumb and index finger without using the knob. I hope the pictures and descriptions presented here will prove useful to other CG-5 owners.
These instructions are also available in PDF format. Click here [719KB].
What Is a CG-5?
The CG-5 is a popular medium-duty equatorial telescope mount available from several manufacturers. Actually, "CG-5" is Celestron International's name for its version of this mount, but other manufacturers sell what appears to be the same mount, and some of them have "borrowed" the CG-5 name. The same mount is sometimes sold as the "EQ-4."
The CG-5 is a copy of the well-known Vixen Great Polaris (GP) mount. The Vixen GP apparently proved so popular that other manufacturers decided to clone the GP and sell it under the CG-5 name. The two mounts are nearly indentical in appearance.
Once you've fixed your CG-5, announce it proudly to the world with Astronomy Boy's official "I Fixed My CG-5" t-shirt! Click here.
Owners of both the Vixen GP and the larger Vixen GP-DX mount have informed me that the descriptions which follow were useful to them in dismantling and improving their mounts. It should noted that, compared to the CG-5, the Vixen mounts usually perform well without extensive refurbishing.
Room for Improvement
By all accounts, one area in which the CG-5 suffers in comparison to the Vixen GP is the smoothness and ease of movement of the Right Ascension (RA) and Declination (Dec) axes. This is attributed to the thick grease used in the CG-5 and the rough finish of its internal mechanical parts. Some users report that motor drives do not work well with the CG-5, due to the stiffness of the moving parts.
CG-5 owners report a marked improvement in the performance of the mount can be realized by disassembling the equatorial head, cleaning out the old grease, cleaning and polishing all internal bearing surfaces, and regreasing. Both of my CG-5s were very stiff, resulting in jerky movements when slewing the telescope by hand. Since I wanted to add motor drives to the mounts, refurbishing the equatorial heads seemed like a good idea.
I searched the web for instructions on how to disassemble the equatorial head but found nothing. Postings in the sci.astro.amateur newsgroup provided some very helpful information, as did private correspondence with other CG-5 owners. In the end, I plunged ahead and dismantled my first CG-5, documenting the experience with a digital camera. These web pages are the result.
The "New" CG-5
Owners of the improved CG-5 report better performance, especially with larger telescopes. I have no personal experience in disassembling or refurbishing the improved mount, but based on correspondence from owners, the procedures presented here should still constitute a useful guide.
In mid-1999, a new and improved version of the CG-5 mount began to appear. The CG-5 was improved with the addition of two ball bearings in the RA axis. Celestron apparently initiated the improved design, so that the mount could better carry the company's 9.25" SCT.
An Even Newer CG-5
More recently, Celestron has released a further improved version of the CG-5. The newest CG-5 is a fully computerized "GoTo" mount with a 40,000 object database and a greatly improved tripod with 2"-diameter tubular legs. This is the same mount that is supplied with Celestron's Advanced Series telescopes, up to and including the company's 11" SCT.
According to owners of this newest CG-5, the procedures on this web site remain useful for improving the mount. However, a word of caution is in order.
One owner of the computerized CG-5 reports that, after completing the improvements described here, the GoTo functions of his mount no longer worked properly. He could not even perform a star alignment with the mount. Fortunately, he discovered that resetting the mount to the factory settings cured the problem, and the GoTo functions of his mount have worked fine ever since. In terms of improving the very sticky Declination axis of his computerized CG-5, the owner reports that the procedures described on this site worked very well.
Since I don't own a computerized CG-5 on which to experiment, I can't confirm that disassembling the mount will always cause a problem with the GoTo system or that resetting to the factory settings will always cure the problem. As stated in the Disclaimer below, I do not take responsibility for your decision to disassemble your CG-5.
Celestron can provide some replacement parts. They do not stock every part for older versions of the mount.
There is no published price list for parts. You must contact Celestron Support and tell them what you need. They will tell you the price of the part if it is available.
P.O. Box 31001-1693
Pasadena, CA 91110-1693
Website: Support Solutions
If you contact them by e-mail, Celestron suggests sending a digital photo to help identify the part you need.
NEW! Another source of CG-5 parts is amateur astronomer George Cushing. George has accumulated a collection of parts for the CG-5 and for certain Meade equatorial mounts. Contact George by e-mail: firstname.lastname@example.org
Improvements from Another CG-5 Owner
Pawel Lancucki is an amateur astronomer and CG-5 owner from Warsaw, Poland. Pawel has made extensive modifications and improvements to his CG-5, including enhancements to the drive controller and a better tripod. He also created some easy to follow instructions for the poorly-documented polar alignment scope. Since Pawel does not yet have a web site of his own, I am providing space at AstronomyBoy.com where he can share his work.
I have not tried Pawel's modifications and instructions myself, but I you may find his ideas interesting.
DISCLAIMER: If you decide to disassemble or adjust your CG-5, it is entirely YOUR responsibility. The purpose of these pages is to show how I improved my own CG-5. I am not a machinist or a mechanic — I have no idea whether any of the procedures I used are "correct" in any sense of the word. Everything I accomplished was achieved through trial and error. You may or may not have the same success I had.
If you wish to use my experience as a guide, you are welcome to do so, but I take no responsibility for the success or failure of your efforts, or for errors and omissions in my descriptions and photos. I am not available to rebuild your mount should you have problems, but I will be happy to answer questions via e-mail.
Also, be aware that some of the materials I used for cleaning and lubricating my CG-5 are hazardous if used improperly. You must take appropriate precautions when using materials such as mineral spirits and synthetic grease. Heed ALL manufacturer's warnings regarding proper handling, ventilation, and exposure to these materials. Your safety is YOUR responsibility.