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iOptron GEM45 and Altair Pillar

My new mount is a iOptron GEM45. This is a German Equatorial Mount that works by tracking the rotation of the earth using the RA axis.

To do this it needs to be Polar aligned. The mount must face Polaris in the northern Hemisphere. To make this easier the mount comes with a camera mounted inside the HA drive, in the centre of the face of the mount. This camera can take a picture of the sky and plate solve where it is pointing. Then it can show you how much to move the mount on the HA and DEC axis to get Polaris exactly in the correct place. (Hr angle) for the mount to be polar aligned. This is call a iPolar camera.

iOptron GEM45 and Altair Pillar

The mount has a very precise RA and DEC worm gears with with 216 teeth with 128X micro-steps, with synchronous belts. (The drives use Synchronous belts to make sure that there is no backlash in the system.) This gives a resolution of 0.08 arcsec (200 PPS) and out the box it has periodic error accuracy of +- 7arcs with a 400 second cycle. However to compensate for this it is possible to program a chip in the RA axis to issue corrections for the RA axis, when tracking which reduces the error to +- 2arcsec. This is known as Permanent Periodic Error Correction. (PPEC). 

Built into base plate is a housing for a guiding scope and guide camera The guiding system is known as a iGuider, but is expensive for what it is. So i have not opted for this system. However i have modified my old guider lense and camera to fit into the housing, which reduces the need and the weight of having a guide camera. 


The lense is a 30mm / 150mm for F5 and the Guide camera is a ZWO mini with pixels of 3.7um. 

With this setup I can guide my setup accurately to a focal length of +- 1700mm with my 600D which has pixel size of 4.3 um or to a focal length of 1850 with my ZWO294MM Mono CCD with 4.63um.

The mount comes with a universal dovetail system with clamps that, can take a Losmondy style dovetail. Build into this base plate is a USB port connected to a USB hub in the mount, and 2 x12v power outputs. This greatly reduces the the clutter around cable management. 


The mount head is very light at 7.2kg, with a counter weight bar that weighs 1kg and a counter weight of 5 kg. It is possible to add a telescope of up to 15kg + camera / corrector / focuser / filters of +- 3kg.  However if you are going to load up this mount, the tripod is not really stable enough. So i have opted for a Altair pillar style base.