Mesu-Mount 200

The mount is based on a friction drive system which is very stiff and efficient, find more info here, driven by a Sidereal Technology servo controller II from Sidereal Technology (USA).

Mount specifications

Drive system
Gear ratio
Meridian flip
Latitude range
Pointing accuracy
Guide accurancy
Periodic error
GOTO speed
Mount control


Friction wheels driven by Servo motors
1 : 2000
0 - 90 degrees
< 2,5'
0,1" with autoguiding
4" peak-to-peak
6 - 8 degrees/sec.
Sidereal Technology Servo II controller and/or PC (planetarium program)

The Mesu-Mount 200

Something about PE (Periodic Error)

The Mesu-Mount with a typical instrument setup is seeing limited for many minutes of open loop tracking (without optical feedback from the object). Measurements are done to demonstrate the Mesu-Mount periodic error over a long period of time under heavy load conditions in open sky conditions. As written in the DFM article more properties than PE are important for a telescope mount.

The Smoothness of tracking is more important than the low frequency periodic error. This is because even a fairly large amplitude periodic error can be guided out using optical feedback (from a guide star) if the frequency is low. If the frequency is high you need expensive systems to guide it out. So it is desirable to have a smooth running mount that does not has high frequent tracking errors.

Optical feedback from a celestial object is what is needed to expose a deep-sky object for a long time. A feedback from the mounts axis to make it rotate very constant will not be enough. This will cost a high resolution encoder to measure the rotation on arc second level and will not help to make a good deep-sky picture. Much better is to use auto guiding and use a celestial object as reference. Auto guiding can be done for a low price and needs to be done anyway also when the mount has a close loop control system on the RA axis. This is because there is variation in atmospheric conditions and flexure in the mechanical parts of the telescope. This factors are becoming more important when exposure times increase. This cannot be compensate by feedback from the mounts RA axis to the servo controller alone.

Another property that defines the mounts quality is the stiffness. Typically telescope structures are stiffer than the drive stiffness, the drive system needs to either have inherent stiffness or develop stiffness through the servo motor controller. Any gear system require lubrication. The lubrication film between the gear teeth will significantly lower the stiffness. The Mesu-Mount is very stiff because it has no gear system that need a lubrication in the drive train.

Furthermore is a high efficiency drive desirable. It requires less power and it allow the drive system to remove energy from the moving telescope setup. Removing energy allows faster deceleration and significantly improves telescope response to position changes. Worm gears with high gear ratio have very low efficiency and must be decelerate very slowly increasing the time required to respond to a position change command.

The Mesu-Mount 200 can be used at any latitude because of its special construction.

The Mesu-Mount 200 on the optional pillar

The Mesu-Mount 200 is also available as a dividable mount exciting of the RA part of 14.5kg and a DEC part of 11,2kg. The declination part can easily be mounted on the RA part. This variant is very suitable for observations in th field.
The dividable Mesu-Mount 200

Price Mesu-Mount 200 : €4.711,00 (excluding transport and VAT)

Image made with this mount

Image of M81/82 made with an 14" ODK on the Mesu-Mount 200. Total exposuretime was 31 hour.
Image made by Oliver Penrice, material is owned by Yves van den Broek (permanent set-up in Southern France).