¶ OpenAstroMount
The OpenAstroMount is a mount meant for larger telescopes that the OpenAstroTracker can't handle. It's fairly heavy and bulky, but can pack quite some payload. It features build in autoPA through motorized ALT and AZ axis. Both RA and DEC are driven entirely by belts, resulting in extremely low backlash. On both axis there is a two-stage belted gearbox with a reduction of 9:1 which, in combination with the large RA and DEC wheels, gives a total reduction of 316:1 and 234:1 for RA and DEC respectively.
The build is fairly involved, not quite cheap and the handling of such a large and heavy mount is not easy. The OpenAstroMount is thus not a good beginners project.
If you are looking for a larger project, you don't have two left hands and you have some entry level knowledge in astrophotography, this is the project for you. Expect at least 1, probably more like 2 months to complete the mount.
¶ Quicklinks
Shoppinglist
Printed Parts
Assembly
¶ Mods and Addons
The OpenAstroMount is intentionally made so you can easily add custom mods and addons to it. Whereever possible, there are mounting points for M3x4.6x6 heated inserts so you can add your own hardware with M3 screws and minimal effort. If you want to add your own addons, see this page: OAM addon mounts
Of course, the generous use of aluminum extrusions means you can also attach a lot of things to those, preferably with M4x12 screws and TNuts/Hammernuts.
One useful addon, since the expectation is that this mount will be computer driven, is to take advantage of the built-in Informational Display capability.
¶ Firmware changes
The online configurator supports OAM directly, so please use that to generate a config.
If you really want to make your own config and not use the configurator, you have to add the following defines to your Configuration_local.hpp:
#define OAM
#define DEC_WHEEL_CIRCUMFERENCE 816.814f
#define RA_STEPPER_SPR (400 * 9) // change to (200 * 9) for 1.8° stepper
#define DEC_STEPPER_SPR (400 * 9) // change to (200 * 9) for 1.8° stepper
#define ALTITUDE_STEPS_PER_ARC_MINUTE ((1640 / 60) * ALT_MICROSTEPPING)
#define AZIMUTH_STEPS_PER_REV (724.0f / (AZ_PULLEY_TEETH * GT2_BELT_PITCH) * AZ_STEPPER_SPR)
#define ALT_MICROSTEPPING 8
#define AZ_MICROSTEPPING 8
Additionally, if not using the new stepper library, define #define RA_SLEW_MICROSTEPPING 2 and #define DEC_SLEW_MICROSTEPPING 2, so slewing doesn't take forever.