Jihghua Mount GOTO conversion by Freddy Díaz

COPYRIGHT NOTICE! This retrofit was done following the instructions of the yahoo roboscope group. You may start with this document: http://groups.yahoo.com/group/RoboScope/files/Retrofit_v1.2.pdf

WARNING!: If you mod your mount you may void it´s warranty! also as power tools are involved, please always work with safety in mind.

 

First the first: Conditioning the mount

The mount is a Chinese mount bought from Apogee Inc (thanks to Steve and Lynn), the name is Jinghua HD. All these Chinese mounts come with a very thick lubricating? grease, it puts a lot of extra load on the motors, the first step, is to get rid of the grease by dissasembling the mount completelly. The full procedure can be reviewed at http://www.astronomyboy.com/cg5/

 

Retrofit

Once the mount was ready the real retrofit work began, no machine shop wanted to make the shaft adapter, I was finally able to convince someone to make the modified shaft adapter, the work was of poor quality and the motors woobled when running at high speed.

 

 

Then recalled the I had some flexible couplers that had the exact 6mm diameter!, what I had to do was to machine the meade shaft to enter on the coupler make a passthrough hole on both axes and insert them on the coupler.

The motors ran very nicely once they got coupled with the flexible coupler, then I needed to patch the autostar in order to work with the EQ mount. In order to communicate with the autostar a cable must be prepared, there are lots of sites with the diagram of the cable, I used same approach that is in the retrofit document. After I made my cable, I was able to get an original Meade cable, checked the pinouts and all were exactly the same.

 

The patch was 34Ec and installed it with the starpatch application please see: http://www.weasner.com/etx/menu.html and http://www.stargps.ca/

After everything was patched, calibrated and ready to test, had to wait until the weather improved, the first real test was done during a  small party (my wife birthday) there were at least 10 people waiting for me to prepare the equipment, there was still sunlight when I started and we were able to see Jupiter and Venus that at the time were very close, however, I noticed that the positioning of the scope was not close to the object I selected.

Later I was able to do some real tests, got dissapointed, the objects were not even in the FOV of the finderscope!, there were like 11 degrees in dec of difference, dismounted everything and began to think on what was going on: after a lot of thinking I recalled I did not do a reset of the autostar!

 

 

Everything is working now and today will be my first star party with the new scope.

Update Dec 2005: I made some measurments of the mount PE and got +/- 20 arc seconds in RA. If I tried guiding goes to +/- 3 arc seconds! After some questions to Roboscope group, I decided to dissasembly the head again and replace the graphite grease with a non suspension grease. I used a red lithium based grease from Texaco.

Now I need to test PEC (periodic error correction) and Guiding.

Update 02/07/06: After months of not being able to test the mount in a star party, finally on Jan 4th 2006, the skies cleared and we had the star party. It was a great experience, with the kids saying oh!, wow! and adults making questions about the moon and saturn (our targets that day).

Unfortunatelly, we were so busy showing and helping people on the file arround the scopes, we did not take any pictures

 

Retrofit II

 

 

In Memorial: Ephraim Kaufman

Freddy Díaz This page was last modified on 17-Mar-2006

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