Takahashi EM-100 mount restoration

Recently I purchased a somewhat challenged Takahashi EM-100 mount with the idea of refurbishing it for use with my Takakashi FS78. This will be used mainly for solar viewing and imaging though a Coronado SM60 h-alpha solar filter.

At first glance it may seem that all the mount needs is a paint job, but after examing pictures on the net of other EM-100's, I could identify several missing or broken parts. Nothing major, but these will need to be replaced by purchasing or machining new parts. Also, after 19 years of use, I figured the bearings could use cleaning and re-greasing.

The age of Takahashi mounts is found in the serial number. EM-100's were made during the 1980's and the serial number shows which year. The serial number of this mount is "9002", which translates to the 2nd mount made in 1989. It is the last year that Takahashi made the EM-100's and as far as I can determine, that only year that they used "Takahashi green" on these mounts. In prior years Takahashi used a dark gray paint. The EM-100 is a very solid mount and according to the Instruction Manual, "the maximum load carrying capacity of the EM-100 mount is approximately 30 lbs." Even if that's a bit of an exaggeration, it should be plenty mount for my 8 lb. FS78

I had some parts I needed, laying around from other projects. Two knobs - one small knob for the end of the counterweight shaft and one large knob for the latitude adjustment screw. These just needed to be bored out and tapped. I then had to machine a shaft to replace the broken slow-motion shaft and then press it into the spur gear. I found two slow-motion knobs on the internet and picked up a couple if 3mm screws for the R.A. gear cover from the local hardware store. I also located a PD-6XY drive controller in Europe and at this time it is still on its way.

The counterweight that arrived from the seller (a little later) proved to be too large for my FS78. It weighs 7 kg. (15.4 lbs) and I could not balance my scope. I tried to locate a smaller counterweight, but without success. So, I decided to machine a new counterweight from an 8 lb. piece of brass I had laying around. I had to sleeve the center hole to fit the EM-100 counterweight shaft and to make a tightening knob.

Next came disassembly. I did this slowly, making notes and taking pictures of each step - 36 pictures total. Here is a picture of the mount fully disassembled. Disassembly is pretty straight forward - loosening screws and nuts and pulling apart. I did not remove the polar scope and decals because I did not want to take the chance of damaging them. Instead, I carefully masked them before painting.

Here is a picture of the painted parts. I used 3-M blue masking tape and it worked very well, with no damage to the decals. The paint is Krylon #2335 "Honey Dew" in a spray can and is a very close match to green that Takahashi uses today. Krylon masks well, goes on easily and dries fast.

Here is the mount reassembled. In this picture you can see the new counterweight, altitude adjustment knob and the two Takahashi black plastic slow-motion knobs. Under the mount is a tripod plate for a Losmandy GM-8. The Takahashi EM-100 base fits perfectly into the center hole of the Losmandy plate, making it easy mount the EM-100. I re-greased with a high-quality lithium based grease. This grease has a low temperature spec, that should make the mount smooth even in winter months that in my neighborhood can go to below zero.

The finished mount with FS78 in the saddle!

Here is the mount on an Davis & Sanford Astro 600 tripod. This is the same tripod Astro-Physics sells for their 400 mount. It makes the setup more portable, while being a solid base for the Takahashi EM-100.

HOME

Questions or comments welcomed by P.J. Anway at:

Email