Gina

It may be worth increasing the main frame size though I could always do that later. Probably best to get something working before worrying about getting the best out of it even it that means going for a slightly reduced printing area I have various ides for different hot ends and extruders. eg. two colour or two type filament printing and also maybe making use of my 3mm filament stocks. I may want to use bigger X carriages to take two extruders etc.

Working on the design of the XY frame component layout, in particular whether to have the motors at the front or the back. Another idea was CoreXYZ but I think that may be too complicated. My Mini printer has the motors at the front as conventional but then the XY plane is fixed and the bed moves for the Z axis. CoreXYZ has the advantage that the XY motors are fixed so the Z carriage (XY frame) is lighter but with using non-stretch cord rated at 80lbs and three or four cords taking the weight I don't think the extra weight of two NEMA 17 motors and their brackets will be too much. It will still be a lot less than the print bed with its thick aluminium plate, heater and all the other bits and pieces. The reason for motors at the front in the more usual CoreXY arrangement is that it leaves the extruder and hot end clear from the front. With a moving XY frame the front frame member obscures the extruder anyway. I don't think I can do without the front frame member. With the XY motors mounted on the frame, their power cables will loop downwards so it's a case of either motors and cables at the front or crossed cords. The cords could be enclosed in a lightweight 3D printed cover but the front piece would be thicker than with the motors at the front. I'll have a play about I think - there may be other things that influence the choice that I haven't thought of. This is my first XYZ nozzle motion printer.

The aluminium plate has arrived. It's flat to nearer than 0.1mm in one direction, with a very slight bow of possibly 0.2mm in 500mm in the other. That would work even without nine point auto-bed-levelling so that's fine. As for scratches, both sides are protected by plastic sheet so none It may well bow when heated from one side but we'll see. The other point is that this plate is bigger than needed. I do have an aluminium cutting disc for my bench electric mitre saw but don't know how well it would cope with 5mm aluminium sheet. Anyway, there's plenty to do before I need to decide.

The 60mm acrylic dome has arrived. I think it would be big enough but on carefully looking through it, i don't think the optical quality is good enough but I'll try it next time we get some clear skies or at least something other than the mist and totally bland grey sky we have at present.

The smaller V groove pulleys are just the job I have attached two on an M5 bolt with washers between bearings and between bottom bearing and V-slot extrusion of the frame with Tee Nuts in the extrusion. This produced a very solid mounting. I think these and the non-stretch fishing line cord will produce a very accurate XY drive, this has certainly proved to be the case with my Titan printer which has smaller V groove pulleys. (I compared the cord and pulley drive with timing belt and pulleys, on my Pilot printer and the cord was noticeably better. The cord has less stretch than timing belt.)

Ooznest delivery is going to be in a day or two but I have received the pulleys from Makers Hut so I can design new Y carriages and sort out the fixings for the ones that go on the XY frame.

Found some 5mm thick plastic foam sheet that had been used for packaging and cut it to size and fastened it to the camera. Also, pieces between camera and heatsink. Now testing...

Left the ASC running overnight though I see it clouded over in the early hours. The camera was covered in a thick layer of ice and temperature was -1.8°C and I guess the ice provided some thermal insulation. What is apparent is that the camera wants thermal insulation when Peltier TEC cooled - I shall look into that today. It is not practical to seal the ASC to keep moisture out so I shall spray the electronics with ACF moisture repellent.

There is one other thing I could do to improve the cooling and that's to add thermal insulation around the camera (except where the focus motor is as there's no gap there). This would have two benefits - stop heat from the TEC hot side getting to the camera and warming it and reduce the effect of the warm air rising from the hot side being cooled by the cold camera and providing more heat for dew heating. It's possible that extra heat from the Peltier TEC could eliminate the need for a dew heater. OTOH lagging the camera could cause it to overheat in daytime making Peltier TEC cooling necessary as the only form of camera cooling.

Here's the latest image - same settings, camera temperature 3.5°C. No dew heating. North is towards brick chimney with cowl, at top of image..

Aha! It's a 12v Peltier TEC but I don't know what power. I also don't know it 12v is it's voltage rating or just the normal working voltage as many nominally 12v TECs are rated at 15v. The only info I've found so far is from a post in my Mk 4 version around 18 months ago :- In the next post I said :- It's still true that I probably don't need a lot of cooling but 5v doesn't seem enough. I guess that answer is to use another buck converter to run the Peltier TEC above 5v but below the observatory main power supply of 13.8v. I also have another possible use for an intermediate voltage and that's for powering the Arduino for my weather station wind sensors if I don't run it from a USB port on the RPi. I have a spare buck converter so I can try this - probably tomorrow as I want to leave the ASC imaging for several hours tonight.

Still clear (mostly). Same settings. Needs hot pixel removal. And I think it could also do with more cooling - temp 3.6°C. Need to check what voltage the Peltier TEC is actually rated at - I thought it was 5v but now I'm not sure.

FITS file viewed in PixInsight.

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

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.

Hoping I'll get a delivery from ooznest tomorrow so that I can continue this project

Well it was tight but I think this is it.

// 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.

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!

Room sized 3D printer :- https://toms3d.org/2017/12/11/building-a-hangprinter/ 3D printers really fascinate me. Been thinking about that "hang printer". I think my workshop, when it's cleared out and "re-furnished" could be used for one of these Apart from the rather complex geometry, I can't see many problems. But I wouldn't want to be limited to PLA and would therefore want a heated print bed. It's difficult to see any way of producing a very large heated bed without spending a small fortune though a 600mm square one would not be out of the question. 300x300mm Square Silicone Rubber Heater Pad w/ thermistor 220V 300W Four of those would be affordable at £136. 6mm Aluminium 5083 Sheet Plate blanks profiles ANY SIZE CUSTOM CUT Free shipping 600mm square costs £113 10mm Aluminium 5083 Sheet Plate blanks profiles ANY SIZE CUSTOM CUT 600mm square costs £175 inc. carriage. 6mm might be alright but 10mm would be better. My 3D printers would be roughly doubling printing area with each model :- Mini 200mm square = 40,000 sq mm (Reference) Titan 300mm square = 90,000 sq mm (80,000) Giant 400mm square = 160,000 sq mm (160,000) Hang 600mm square = 360,000 sq mm (320,000)

This blog is for a discussion about designing and possibly building ever bigger 3D printers.

Moon is lighting the ground up now.

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

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.

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