NEMA 14 mounting - M3 on a 26mm square.  22mm x 2mm raised round part.

Focus motor mounting plate - also centres casing onto camera.

The NEMA 14 motor is a tight fit and the mounting plate has needed slight alteration.  The motor moving slightly outwards and a mm taking off the underside of the plate to make the motor fit.  This screenshot shows the model as for printing - upside down.

That works fine - focus motor fits perfectly

Impressive.

Now designing the gears for the focuser.  Distance between centres = 49mm so I think I'll make the gear radii 40mm and 9mm with 40t and 9t ie. mod 2.

Gears designed and now printing.

Prints are fine   Need to find the lens for testing!  No, it hasn't turned up yet.

Found the lens   Now checking the gears - slight adjustment needed.

Here is the full focussing system (except for plugging in the motor cable).  Pinion printed in TPU flexible filament for easy attachment to motor shaft.

Connected everything up and ran all the firmware/software operating the focuse resulted in the motor just twitching so I checked the connections and the NEMA 14 is NOT connected as per RAMPS so I had to extract a couple of the connector "pins" and swap them over.  Now to try again...

That's better - remote focus working

This screenshot of the KStars Fits Viewer shows camera on the table and focused of the mess of wires.  If it stops raining I'll put the casing on and hook it on the guttering and test it on the distant lights or if I'm really lucky, stars.

Stopped raining and some clear sky   The focus is not quite even across the field - it may need some pressure applied to the lens thread tho stop the slop.  Settings :- Exposure 10s gain 240 gamma 50 (1.0).  No dew heater and no camera cooling.

Some more, gamma reduced to 20, WB adjusted.  It could do with the camera cooler on.  Probably sort that out tomorrow.  Dew heater too though no dew ATM.

Clouded right over now.  Oh well...

I shall need to look at the standard focuser code and alter it.  ATM it starts off at zero and will only go positive - "focus outwards".  It loses the current focus count when disconnected then when switched back on the software thinks the focus count is zero and will only go positive ie. will only focus one way.  So I have either to arrange that it saves the current focus position of is able to go negative as well as positive. 

There is "Parking Mode" where the focuser is moved to the zero position when disconnecting - provided the Disconnect button is used rather than just cutting power.  But then the focus must be adjusted after starting up as the focus position isn't held, though I guess you could write down the focus count and go back to it.  None of this is exactly "user friendly".

ASC in its casing showing the focuser.

The moon is just below the horizon but lighting the clouds to the east...

Focused on the stars rather than distant lights - there was a difference.  I think this is about the limit of the lens resolution and colour registration.  Of course, this is just one sub and only 10s with no cooling.

This is 30s exposure with gain of 95 and gamma 20.  Moon is just above the eastern horizon, shining through the cloud.

Moon is lighting the ground up now.

I think I'm happy enough with the focussing so next will be to add the circuitry for the camera cooling and dew heater closely followed by sorting out the cover dome operation and casing.  There's also the Wi-Fi but I think I'm beginning to see the light at the end of the tunnel   Just as well as this project has been taking far too long!

// Power lines
#define IN2 RPI_BPLUS_GPIO_J8_32	// GPIO12  Dew Heater
#define IN3 RPI_BPLUS_GPIO_J8_33	// GPIO13  Camera Cooler

Here is a start on the design of the circuitry for dew heater and camera cooling control.  Space is at a premium - the optocouplers are 3 holes wide and effectively occupy 4 holes so won't fit within the left hand batch of 5 holes on the HAT.

Well it was tight but I think this is it.

Camera Cooling on.  Dew heating unnecessary.  10s exposure, gain 96, gamma 30, temp 4°C.  Must rig up a shield for the neighbour's floodlight.

Yippee - they've turned it off   New image - 30s exp, gain 200, gamma 10, temp 4.2°C.