Our equipment posts cover the making, modification and use of observatories, telescopes and equipment. Select the posts for more information on the topics.

Mesu e200 Mount Unboxing and Assembly

I recently bought a Mesu e200 (also know as the Mesu MKII) mount. This mount uses friction rather than gears so doesn’t have any backlash, it is incredibly accurate and can handle a load of 100Kg (that’s 18 stone! or over 200lb!)

Check-out the video for the full unboxing and assembly – the video isn’t a review but you will get an idea of the quality from this video. Whilst the mount is expensive, it is far more economical than equivalent mounts, other owners have sold their Paramount’s  in order to fund buying more of these – they really are good.

 

EQ6 Belt Drive Mod

EQ6-belt-mod0
The EQ6 Belt mod replaces the brass gears with a timing belt to reduce errors and remove backlash.

The EQ6 has standard brass gears on the stepper motor and worm gear, with a ‘transfer’ gear to translate the stepper motion to the worm gear.

These gears introduce errors and backlash, the belt drive mod is designed to replace these gears with a timing belt

EQ6-belt-mod1
The old and new parts

Replacement of the gears for a belt drive is straightforward but will take a day to do properly. Instructions are provided with the kit from Rowan Astronomy and another useful resource is the hyper-tune instructions from astro-baby.com

There are a couple of tricky steps

  1. Removing the adapter at the bottom of the polar scope shaft – you will need a steal belt, oil filter wrench (from Halfords)
  2. Removing the worm gear caps and the worm gear retaining ring, these can be removed using pointed pose plyers, but you risk damaging the caps if you slip, a better approach is to use the specially designed tool (available from Rowan Astronomy)
  3. The bolts holding the mount together are steel bolts with M6 threads tapped into the aluminium body – it is very easy to strip the threads be vary careful – if you do strip them you can repair them easily with a Helicoil thread repair kit.

EQ6-belt-mod2
Some of the tricky steps

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Threading the belts through the guides can also be tricky, locking tweezers help a lot!

Fitting the belts is easier if you have locking tweezers, but it can be done with your fingers – if you are nimble – there is not much room to manoeuvre inside the mount.

EQ6-belt-mod4
The disassembly required to fit the belt mod.

EQ6 Hyper Tune

The EQ6 hyper tune is a procedure to strip down and rebuild your mount to improve performance, the exact details are best followed from astro-baby.com so I won’t copy them here. The tune-up includes replacing the plastic shims and replacing them with PTFE ones and replacing the bearings, I replaced the small worm gear bearings and cleaned and re-greased the large bearings.

The best attitude to take when doing this modification is slow and deliberate, if something is not going well or as described in the instructions the best course of action is to stop, have a cup of tea, re-read the instructions and try again.

I took the time to make-up an EQ6 tool set, this includes all the tools needed for the hyper tume, most are common tools you are likely to have available such as screwdrivers and allen keys, the two less common tools are the metal band oil filter wrench (available from Halfords) and the worm bearing cap and retainer removal tool (available from Rowan Astronomy – makers of the EQ6 belt drive mod) the latter you can get away with pointy nosed plyers but you are more likely to scratch the caps without the tool.

 

EQ6-Tools
All the tools needed for a strip-down and rebuild of the EQ6 mount. A long flat-bladed screwdriver, digital micrometre and locking tweezers are also useful but not essential.

The strip-down and rebuild took a total of 20 hours, requires a lot of space and somewhere reasonably clean to lay everything out. It is straightforward if you are mechanically minded, but is a large commitment of time. 

To complete the hyper tune required the following parts and consumables.

  • 2 rolls of paper towels
  • 2L of white spirit
  • old tooth brush – for cleaning parts
  • clean containers – e.g. ice cream tubs for cleaning parts
  • lithium grease for re-greasing bearings and all parts
  • PTFE shims of various thicknesses to replace the plastic shims 
  • New bearings (I just changed the small worm gear bearings)

Expect to spend about £60 on these parts

EQ6-HyperTune2
EQ6 parts laid out on the workbench, note the old (bottom middle) and new PTFE shims (bottom left)

There was a lot of dirt and grit in the main bearings, quite how this gets in, given they have never been taken apart, is beyond me. To re-grease them requires removing the bearing caps that seal the bearings in, this was done using a modified modelling knife. The bearings were then de-greased using white spirit, the process of removing all the dirt from the bearings took a long time, we kept spinning the bearings in the white spirit to dislodge the dirt until no bits were visible in the pot, regularly changing the white spirit. They were then left to dry naturally on paper towel and before re-greasing were warmed with a hot air gun to ensure all the white spirit had evaporated.

EQ6-HyperTune1
Cleaning all the parts

Any parts that required cosmetic repairs were repainted and I also replaced all the rusty screws with new ones.

When we reassembled the EQ6 the Declination worm felt ‘notchy’, so we took the EQ6 apart again and inspected the worm gear, it had a small surface scratch, almost too small to see, but this scratch was getting amplified in the mount, so we polished it out using 2000 grip emery paper on a lathe (you could probably do this in a drill if you don’t have a lathe), this cured the problem.

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Declination worm gear being repaired on the lathe, which was simply a matter of polishing out a surface scratch.

A massive thank you to Julian Tworek for offering to help complete the hyper-tune, Julian’s patience, experience and perfectionism is exactly what is required to complete this project successfully.

EQ6 Locking Power Mod

The EQ6 is known for its power connector coming out or momentarily disconnecting, which is not something you want happening in the middle of an imaging session. I’d previously replaced all my power connectors to a type with a locking collar and decided to mod my EQ6 so that all my gear uses the same connector. This is not a particularly hard mod if you are confident around electronics and a soldering iron, but it will obviously void your warranty. You have to choose where to fit the connector carefully to avoid any components on the motherboard. Tapping onto the 12v on the board is pretty easy but worth checking with a multi-meter.

EQ6-locking-powwr-mod

Super Smooth EQ6 Altitude Adjustment Mod

The EQ6 is difficult to polar align in Altitude, especially when fully loaded, the Knobs Mod can help, but only so far because the design of the altitude adjustment is flawed. Modern Astronomy  make a ‘rail mod’ this corrects the design and makes precise polar alignment in altitude really smooth. I won’t go into the installation here, but it is straightforward, the altitude bearing/bolt covers are liekly to be damaged when you remove them (I got mine off ok but this is apparently unusual) so the kit does come with some nice metal new ones (although I prefer the originals).

Concept

 

EQ6-slide-mod-concept

Getting the altitude bearing bolt covers off is the hardest part of this mod, you will likely destroy them, fortunately the kit from Modern Astronomy comes with some new ones.

EQ6-Altitude-slide-mod

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