Astro-Physics 900 GTO
Measurement of the PE using Pempro, 7 worm cycles, after 3 years of use, no PEM: a mount which tracks!!!
Measurement of the periodic error on three worm cycles, PEM not activated
The mount in action
And my comments:
I will never regret my choice..
This mount is a true marvel of technology. Its size and weight are very limited regarding its load capacity, thanks to the CNC machining and compact design.
It is very rigid, which is really important in CCD imaging, when using an long instrument like a refractor, or when using a piggyback instrument.
It carries easily the 155 f7 StarFire EDF refractor, with its finderscope, in various configurations: with our without heavy guidescope, rings and guider, two mounting plates, heavy CCD camera, and field flattener or telecompressor.
I decided to mount it on a Losmandy G11 tripod, using the LT2APM adapter. Setup is rock solid, and levelling easy on uneven terrain.
Tracking and pointing accuracies are outstanding: with a well mounted orthogonal instrument like the refractor, the object is always centered on the CCD chip, even after a meridian flip. By the way, this is also the real advantage of this mount : its ability to continue to track well after the meridian,without having to flip, with the instrument "below" the mount, with no sign of degradation in tracking performance.
The periodic error is very small and low, between 4 to 5.5 arc seconds error, depending on tooth to tooth error of the worm wheel. Variations in the error curve are extremely low, so autoguiding using long guiding exposure times can be made without trouble: extremely useful with narrowband filtered imaging.
The three stars polarscope is very accurate: once polar aligned, without additional effort, I can do more than 6 hours of imaging with my camera without noticeable field rotation, even with the large chip of the STL11000.
Mount's control doesn't need a computer , this is precious when a computer failure occurs in the field.
Several features like focusing, reticle, can be ajusted with the keypad.
I would definitely recommend this mount, technically as well as aesthetically, for the visual observer or demanding imager.
Gilles COHEN
I will never regret my choice..
This mount is a true marvel of technology. Its size and weight are very limited regarding its load capacity, thanks to the CNC machining and compact design.
It is very rigid, which is really important in CCD imaging, when using an long instrument like a refractor, or when using a piggyback instrument.
It carries easily the 155 f7 StarFire EDF refractor, with its finderscope, in various configurations: with our without heavy guidescope, rings and guider, two mounting plates, heavy CCD camera, and field flattener or telecompressor.
I decided to mount it on a Losmandy G11 tripod, using the LT2APM adapter. Setup is rock solid, and levelling easy on uneven terrain.
Tracking and pointing accuracies are outstanding: with a well mounted orthogonal instrument like the refractor, the object is always centered on the CCD chip, even after a meridian flip. By the way, this is also the real advantage of this mount : its ability to continue to track well after the meridian,without having to flip, with the instrument "below" the mount, with no sign of degradation in tracking performance.
The periodic error is very small and low, between 4 to 5.5 arc seconds error, depending on tooth to tooth error of the worm wheel. Variations in the error curve are extremely low, so autoguiding using long guiding exposure times can be made without trouble: extremely useful with narrowband filtered imaging.
The three stars polarscope is very accurate: once polar aligned, without additional effort, I can do more than 6 hours of imaging with my camera without noticeable field rotation, even with the large chip of the STL11000.
Mount's control doesn't need a computer , this is precious when a computer failure occurs in the field.
Several features like focusing, reticle, can be ajusted with the keypad.
I would definitely recommend this mount, technically as well as aesthetically, for the visual observer or demanding imager.
Gilles COHEN
Tracking performance, autoguiding using dithering. Guiding exposure 3 seconds, 10 minutes single exposure, ST8XME camera.
Some concrete measurements:
Another screenshot in MaximDL, autoguiding using dithering. Guiding exposure 4 seconds, 15 minutes single exposure, STL11000 XM camera.
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