MountOne | Assembly.

Don't Panic!

This guide is 99% images.

Index.

Printed Parts.

For information on printing the parts for the MountOne, please refer to the MountOne Printed Parts Documentation.

Electronics & Fixings.

The MountOne Hardware Kit includes the following required components & fixings.

  • 2 x 0.9° Stepper Motors & Cables.
  • 4 x 6811-2RS Bearings.
  • 32 x MF148ZZ Bearings.
  • 10 x 80mm Long 8mm Diameter Bars.
  • 1 x Power Slip-Ring.
  • 1 x Signal Slip-Ring.
  • 3 x DC Female Sockets
  • 2 x DC Male Plugs.
  • 1 x DC Male Angled Plug with 2m cable.
  • 6 x 3GT 213T Loop-Belts.
  • 2 x 3GT 237T Loop-Belts.
  • 2 x 3GT 348T Loop-Belts.
  • 2 x 20T 3GT Pulleys.
  • 72 x M5 20mm Screws for Plastic.
  • 24 x M2.5 8mm Screws for Plastic.
  • 12 x M3 8mm Countersunk Bolts.
  • 4 x M3 10mm Standoffs.
  • 4 x M3 5mm Socket Cap Screws.

Parts you will need to source yourself.

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

We go through the software setup in the MountOne Software Documentation. This guide is solely for the purpose of the hardware assembly.

Assembly.

The build is split into three phases.

  1. Right Ascension.
  2. Declination.
  3. Final Assembly.

Phase 2. Declination is a repeat of the instructions of Phase 1. Right Ascension as all the parts are the same, except for the main housings (M1-RA-72.XXx1.stl & M1-DEC-72.XXx1.stl). There are minor differences in the wiring too, but this is noted in the guide.

You are more than welcome to combine Phases 1 & 2 by doubling the part count in the relevant sections, for example, assembling eight idlers instead of the instructed four.

Can you use an electric screwdriver to assemble the MountOne? 

Yes, but I don't recommend it. Firstly, unless the driver has adjustable torque, there is a risk you will strip the threads. Secondly, the increased speed an electric screwdriver can provide can induce excessive heat, through friction, potentially melting and weakening the plastic. 

If you do use an electric screwdriver, set the torque to the lowest setting, and run it at it's slowest speed. Hand-tighten the screws afterwards to get the right tension. Perhaps perform a few test screwings to see how it performs, and adjust your screwing based on that research. 

Right Ascension.

Pulleys.

Press two MF148ZZ bearings into each of the four smaller compound pulleys.

Ensure the bearing flanges sit flush against the pulleys. They usually require a certain amount of encouragement. Do not hammer them in.

It is possible to test the bearings are inserted correctly by passing one of the 8mm bars through the pulley.

Idlers.

Install two MF148ZZ bearings into each of the four idlers.

Idler Arms.

Assemble the four idler arms, each arm sandwiches an idler and is fixed in place with three M2.5 8mm Screws For Plastic. These arms are used to tension the belts.

Drive Motor.

Note the orientation of the motor plate, with the 'pointy end' orientated to align with the motor's cable connector. Note too the countersunk holes facing upwards.

Four M3 8mm Countersunk screws secure the plate to the motor.

Drive Motor Pulley.

The centre of the tooth profile should be 14.7mm (±) 0.5mm from the front of the motor plate.

Bars.

Four bars are installed into the main housing.

They will require some jiggling to ensure they are fully seated into the housing.

Two spacers go onto the two bars the pulleys will run on.

Install the first pulley onto the bar as shown.

Fitting The Drive Motor.

Make sure you select the correct 237mm loop belt.

Loop the belt around the motor pulley and run it around the compound pulley.

Four M5 20mm Screws For Plastic secure the motor in place. Tighten the screws and then back them off a quarter of a turn, the motor needs to be able to move freely so we can set the belt's tension later.

A small tension adjuster sits in front of the motor. The further in the screw is set, the greater the tension on the belt. For now, we don't want any tension on the belt, screw in the screw until you can just feel the adjuster beginning to move.

The Belt-Drive.

Install a second compound pulley.

Place spacers on top of each of the two installed compound pulleys.

Select a 213mm belt.

Fit it between the two compound pulleys as shown. It can help to rotate the pulleys while trying to install the belt. Note that rotating the pulleys will become harder the more pulleys there are.

Before installing the next compound pulley, a tension arm and tension adjust must be installed. In this case arm A is required.

In all cases, the screws in the arms should be facing upwards.

After installing the arm, fit a large spacer on top. The tension adjuster should be fitted too. As before with the motor, we do not wish to apply tension to the belt at this time.

Fit a third compound pulley and belt.

Tension arm B is fitted along with a tension adjuster and a spacer.

Install the fourth compound pulley and belt.

Before continuing, install two spacers on top of the two compound pulleys.

Install tension arm C and a tension adjuster. No spacer this time.

6811-2RS Main Bearings.

Press-fit in a single 6811-2RS bearing. These should be a tight fit.

Install the inner and outer bearing spacers.

Install the second 6811-2RS bearing.

Fit the large bearing cap using six M5 20mm Screws For Plastic.

Install tension arm D.

The D tension adjuster attaches to the brace.

With the 348mm belt in position, place the brace on top of the belt-drive.

There will be some resistance when installing the brace. You'll likely have to jiggle the bars around to get them to slot into their relative holes. Be careful not to damage the compound pulleys if leverage is required. It will take a firm press to ensure the brace is seated.

The brace should sit flush against the housing when installed correctly.

Four M5 20mm Screws For Plastic fix the brace in place.

Drive Output.

Slide the drive output into the bearings from the underside.

You may need to align the inner bearing spacer for the drive output to pass through.

Person-handle the 100T main drive pulley into the 348mm belt.

Align the pulley with the drive output and press it into the main bearing. Check the belt and pulley teeth are correctly engaged.

Secure using six M5 20mm Screws For Plastic.

The RA Cables.

The RA Slip Ring takes in power and distributes it to the OnStep PCB, and out the DEC Slip Ring to provide power to the astrographs.

Plug in the motor cable.

Setting The Belt Tension.

There are five screws used to set the belt tensions. Tighten the screws (don't use an electric drill), until you feel an increase in the torque needed to turn the screw driver. 

After the belts, tighten the four screws securing the motor.

The Right Ascension (RA) is now completed.

The Declination.

The build process is identical to the Right Ascension. You can jump back up to the top and follow the instructions again. Or if you were combining Phases 1 & 2, carry on down the page.

The DEC Cables.

The Declination Slip Ring features 12 circuits. These circuits carry power, serial and connections for two stepper motors.

The Declination is now completed.

Final Assembly.

The Right Ascension and the Declination need to be attached together.

To add strength to the assembly, two 8mm bars bridge between the RA & DEC housings. These need to be installed first.

They should fit into the RA housing as shown.

The DEC housing slides down the bars onto the RA. Check the cables are not trapped between the two parts.

Check the Declination (DEC) seats fully down on to the RA.

There may be a ledge at the front, this is fine, and is compensated for.

They should align at the corners.

Secure the RA & DEC together using six M5 20mm Screws For Plastic.

The Electronics.

Using four M3 countersunk bolts, affix four M3 standoffs.

Bolt the Electronics bracket to the main assembly using two M5 20mm Screws For Plastic.

The Wiring.

I have marked the RA & DEC motor cables with R & D for easy identification later on.

The technique I use for doing the wiring is lots of adjustment, application of cables ties, cutting off of cables ties, more adjustment, more cable ties, more cutting off cable ties, then adjustment and final cable ties.

The important things to note are; the Orange & White 2-Pin housing needs to go to the left side for connection to the MaxPCB4's UART header. All the other connectors go to the right. 

It is also important to keep the cables clear of the moving parts. It will take a bit of fine adjustment, and don't be afraid to cut off cable ties and readjust.

In the end it is all held together with just three cables ties, but I went through about 6 others before it was finished.

The MaxPCB4.

I am going to assume that you followed the instructions set out in the MountOne Electronics documentation and everything is ready to be installed. 

Install the MaxPCB4 with the Teensy in the top left corner. Four M3 6mm Bolts hold it in place.

Plug the Orange & White 2-Pin into the UART header (Orange at the top).

The angled DC Jack supplies power to the MaxPCB4.

The RA & DEC motors connect to their respective headers on the board (RA at the top, the board is labelled). Check both have the black wire towards the top. This is important at is influences the direction of the motors.

The two 4-Pin headers from the DEC Slip Ring plug into the ROT (Green & Purple / Brown & Blue) for the de-rotator, and the FOC (Blue & Yellow / Pink & Grey) for the focuser.

None of the astrographs currently use the de-rotator (ROT), however it does leave the option open to future developments.

The focuser (FOC) is used by both the 100MM & 102OTA Astrographs.

The Cover.

The cover is held on with two M5 20mm Screws For Plastic.

Fixturing.

The MountOne can be attached to both standard tripods, and the Printed Equatorial Tripod (PET).

If you are making the PET, the printed part M1-TRIPOD-UNCx1.stl is replaced with M1-PET-BASE-WEDGEx1.stl. Details are in the Printed Equatorial Tripod Documentation.

You will need (these parts are all included in the MountOne Hardware Kit).

  • 1 x M1-TRIPOD-UNCx1.stl or M1-PET-BASE-WEDGEx1.stl
  • 1 x 1/4-20 UNC Rivnut.
  • 1 x DC Jack.
  • 1 x DC Socket.
  • 1 x Length of wire.

The 1/4-20 UNC Rivnut needs to be pressed firmly into the printed part.

The Rivnut should be accessible from the underside. It is intentionally difficult to install.

Remove the washer and nut from the DC Socket.

Prepare an approximately 120mm length of cable.

Strip and tin the ends, and don't forget the heatshrink.

The cable with the white strip down it's length is the positive (+) and will be soldered to the centre pin.

Pass the cable through the hole in the front of the printed part.

Push the DC Socket fully in.

Remove the case from the DC Jack.....

.....and slide it tail-first over the cable.

Strip and tin the ends. Add heatshrink.

Solder the ends to the DC Jack and crimp the cable.

Reinstall the case.

We shall use six M5 20mm Screws For Plastic to attach the base to the main assembly.

Connect the two leads.

Screw on the base. It doesn't matter which orientation you use, so long as the holes all align for the screws.

I am attaching a small desk tripod to the MountOne. You can of course use a standard tripod, or the Printed Equatorial Tripod (PET).

Power On.

Remove the cover and recheck the wiring.

If all is good, plug in the power.

The D1 Mini will power on first, shortly followed by the Teensy. You may also hear the motors energise. There should be no magic smoke.

I am using the Smart Hand Controller (SHC) to control the MountOne to move the MountOne to a more accessible position. There is also an OnStep App available if you wish to use your phone instead.

To check the MountOne is working correctly, we can use the SHC, or app, to control it's movement. To be able to do this we must enable tracking.

Setting the guide speed to max will significantly increase the speed.

We need to test both the Right Ascension (RA) and the Declination (DEC).

When you are happy everything is functioning correctly, power off the MountOne and refit the cover.

The MountOne is now ready for an Astrograph!

Glamour Shots.

Back to the MountOne Documentation.