Mesu-Mount 200 review

The Mesu-Mount 200 is unlike any other mount you will have seen before.

Finished in stainless steel, black silk powdercoat and anodised alloy, it is a triumph of function over form.

If you insist on sweeping curves and soft edges, you won’t find them here, but what you will find is solid, high-quality engineering.

This mount is a pure engineering solution to a well-established problem – how to accurately locate and track celestial objects.

When the Mesu-Mount 200 was originally released it shipped with a ServoCat mount controller for basic operation and an Argo Navis Digital Telescope Computer hand controller to add full Go-To functionality.

Although this system worked very well, there were calls for full robotic control from imagers who required greater computer integration.

Mesu listened to this feedback – the latest version reviewed here comes with the well-respected and versatile SiTech Servo II controller from Sidereal Technology.

The SiTech controller is a customisable system comprising an electronic interface and processor, ASCOM-compatible but slightly quirky mount control software and a simple hand controller.

Various additional software tools are included to implement ‘plate solving’ (a very accurate method of determining exactly where your telescope is pointing) software-assisted polar alignment and automatic multi-point sky modelling.

Each of these helps to improve the mount’s Go-To accuracy.

Lifting the mount onto a pier or tripod is really a two-person task, as it weighs 25.7kg.

However, assembly was straightforward, requiring approximate adjustment for your latitude, the attachment of the optional Losmandy- or Vixen-compatible saddle clamp using four socket head bolts and the positioning of a 40mm-diameter counterweight bar into the base of the declination axis.

The counterbalance bar has a neat ‘detent’, a device that stops it from sliding out of the mount head, and an undercut and toe protector to ensure that the counterbalance weights cannot inadvertently slip off.

The mount is attached to the optional mounting plate with a single central 12mm bolt.

Counterweights are not included as standard, but are available in various weights from third-party suppliers.

Chrome-plated 5kg and 10kg Geoptik weights were supplied for the purposes of this review.

Technical prowess

A bracket-mounted polarscope is available as an optional extra, but as this wasn’t supplied with the review unit we used the SiTech’s built-in polar alignment routine and achieved a satisfactory alignment.

Adjusting the altitude and azimuth settings was extremely easy using the substantial knurled knobs, having first selected the correct mounting hole for the eyebolt in the stainless steel altitude quadrant.

The unusual friction drive is permanently connected, so there are no clutches as such, but the right ascension and declination axes can be locked by engaging two rotating, key-shaped hooks, which slot into matching cut-outs in each axis.

With the hooks disengaged, the axes rotate freely, allowing accurate balancing to be carried out after the telescope has been attached.

As the friction drive eliminates backlash, it is not necessary to offset the balance for autoguiding as you have to with a worm gear drive.

After carrying out a basic two-star alignment the Go-To was very accurate, with test stars appearing near the centre of our CCD sensor each time.

Go-To accuracy was further improved by adding more alignment stars.

The Mesu-Mount 200 will be of particular interest to astrophotographers so we were keen to see how it lived up to its specification regarding periodic error, which has a large effect on image quality and star shapes.

The lower the periodicerror the better and in our tests we measured this at 4.37 arcseconds peak to peak (1.22 arcseconds root mean squared), which was an excellent result close to the manufacturer’s claim.

We would highly recommend this mount to any advanced astrophotographer wishing to make the leap to a true observatory-class imaging mount.

This review appeared in the June 2013 issue of BBC Sky at Night Magazine