MountOne | 100MM Assembly.

Don't Panic!

This guide is 99% images.

Index.

Printed Parts.

The MountOne & Astrographs were developed with Bambu Lab PLA-CF. Final testing and checks were performed with Bambu Lab PETG-CF. Parts were printed using E3D's A1 Series High Flow ObXidian 0.4mm Nozzle. I recommend PETG-CF for the MountOne and Astrographs. For best results, dry your filament before use.

Full details on how to print these parts are in the 100MM Printed Parts Documentation.

Electronics & Fixings.

The 100MM Astrograph Hardware Kit includes the following required components & fixings.

  • 1 x 100mm f3.5 Apochromatic Lens.
  • 1 x 0.9° Stepper Motor & Cable.
  • 1 x Hexaxes GPIO Highjacker.
  • 2 x 6811-2RS Bearings.
  • 1 x 3GT 264T Loop-Belt.
  • 1 x 20T 3GT Pulley.
  • 28 x M5 20mm Screws for Plastic.
  • 10 x M2.5 8mm Screws for Plastic.
  • 4 x M3 8mm Countersunk Bolts.
  • 4 x M2.5 15mm Hex Standoffs.
  • 4 x M2.5 4mm Bolts.
  • 5 x M2 6mm Bolts.
  • 1 x 1/4-20 UNC Bolt.

Parts you will need to source yourself.

  • Raspberry Pi 4/5.
  • Raspberry Pi HQ Camera
  • Raspberry Pi 5 Active Cooler (Optional).
  • Raspberry Pi M.2 HAT (Optional).
  • 5V DC/DC Converter.
  • Adafruit Ultimate GPS (Optional).
  • Various Cables & Wires.

If you have downloaded the MountOne 100MM CAD Pack, there is a full BOM inside.

We go through the software setup in the 100MM Astrograph Software documentation. This guide is solely for the purpose of the hardware assembly.

Raspberry Pi 4/5.

The Raspberry Pi is secured to the housing using four M2.5 Standoffs.

GPIO Highjacker.

The GPIO Highjacker was developed specifically for use with the MountOne Astrographs with the aim of making the GPIO more accessible and improving the wiring. Full story on the Blog Post. 

The GPIO Highjacker breaks out power (5v & 3.3v), i2c, five UARTS and provides headers to input 5V from DC/DC converters while still allowing the use of HATs. 

Full details | GPIO Highjacker.

M.2 HAT.

Four M2.5 6mm bolts hold on the M.2 HAT (Don't forget the FFC).

GPS.

I have had mixed results with the Adafruit Ultimate GPS. Note the orientation of the pins (they are towards the rear). Two M2 6mm bolts secure it in place.

5V DC/DC Converter.

Three M2.5 6mm bolts affix the DC/DC Converter.

The Wiring.

I'm not going to provide a wiring schematic as there are too many different combinations of the DC/DC converters and GPS Modules to do so effectively. Check the datasheets for each module you are using and confirm the connections and wiring aligns with the input on the GPIO Highjacker, or GPIO. It is pretty straight forward. Note that for UARTS Tx on one module connects with Rx on the other, etc.

However, there are predefined connections for the wiring harness from the MountOne and we need to conform with those. We'll be using eight wires, UART Tx/Rx, +5v/GND and a motor connector. Check the motor phases match the MaxPCB4. Refer to the MountOne Electronics documentation for additional information.

Note: The Raspberry Pi can draw more than 1.5A from the DC/DC Converter. Make sure you use higher-rated (~5A) wire for the power from the DC/DC Converter to the Raspberry Pi. Using the incorrect cable can result in low voltage warnings.

The Bearings.

The two 6811-2RS bearings stack together and go onto the focus ring.

Six M2.5 8mm Screws For Plastic secure the bearing clamp in place. I advise doing them up in a sequence whereby you tighten the furthest screw away from the previous.

The HQ Camera.

Loosely fit the 1/4-20 UNC Bolt and M2.5 Screws For Plastic.

Gently tighten the UNC Bolt and M2.5 Screws.

Take care to keep the camera module centred and fully tighten the Screws and UNC Bolt.

The Camera Focus Module.

Press the focus ring into the housing. Note the orientation.

Place the camera module onto the housing, over the bearings. Push down fully.

Secure using four M5 20mm Screws For Plastic.

You can read about, and download the printed HNDL here | HNDL

Focus Motor.

Place the motor bracket onto the motor, note the orientation of the cable connector.

Secure using four M3 8mm Countersunk Bolts.

Pulley.

The centre of the teeth on the pulley need to be ~14.7mm from the face of the motor bracket.

Fitting The Belt.

Place the motor into the housing as shown.

Stretch the belt around the pulley and then the focus ring.

Secure the motor with four M5 20mm Screws For Plastic, do no tighten them yet.

Belt Tension.

Install the tension block as shown. Tension the belt.

This system is designed to keep any stress or strain from the tensioned belt away from the lens and camera module preventing damage to expensive parts.

Tighten the M5 screws securing the motor bracket.

Main Assembly.

Firstly install the electronics to the main housing using four M5 20mm Screws For Plastic.

Next, install the focus module with five M5 20mm Screws For Plastic.

The Lens.

Remove the cover on the HQ Camera to expose the sensor, and remove the cover on the lens. Needless to say, keep everything clean and clear of dust and debris.

Screw the lens onto the camera module. Make sure the CS > C-Mount adapter is still attached to the camera module.

Once the lens has been fully tightened, using the focus ring wind in the lens focus.

The Lens Cover.

Install the lens cover using two M5 20mm Screws For Plastic. I apologize in advance that this is a bit of a PITA to do.

Cables.

Plug in the motor and camera cables.

The Main Cover.

Install the main cover with two M5 20mm Screws For Plastic.

Filters.

The 100MM Lens is compatible with 40.5mm filters. In this instance I have fitted a UV IR Cut Filter.

Mounting the Astrograph.

Remove the cover from the astrograph. Obviously, you'll need to have assembled and tested the MountOne before doing so.

Pass the cables through the centre.

Six M5 20mm Screws For Plastic bolt the astrograph to the MountOne.

Connect the astrograph to the MountOne.

For easy access I am attaching the MountOne to a desk tripod. You can just as easily use a standard tripod, or the Printed Equatorial Tripod (PET).

Check the wiring. The 100MM requires a third Stepper Driver be installed in the FOC position on the MaxPCB4.

Make sure the motor wiring is correct!

The additional FOC motor should copy the wiring for the other stepper motors (this passes through the DEC Slip Ring).

When you are certain all is well, connect the power.

There should be no magic smoke.

I am using the Smart Hand Controller (SHC) to control the MountOne to move the astrograph to a more accessible position. We will also use it to check the focus functions as expected.

There is also an OnStep App available if you wish to use your phone instead.

The focuser moves slowly at first, but increases speed the longer you hold down the button. 

If everything is working correctly, power down the Raspberry Pi, disconnect the power and refit the covers. 

Next we will install and configure the software.

Glamour Shots.

Continue to the 100MM Software Documentation.

Back to Main Documentation.