Diy DewHeater/Mask/Flats/Cover

[upahill]

Need some help with a sanity check. Have been trying to get my head around being able to cover the scope for darks, use a flat panel, and use a mask from the comfort of my living room without the constant trips in and out. It's not too bad at the moment but when there is 3 foot of snow on the ground and a clear night it wont be pleasant.

I knocked this idea up last night, and thought I could even integrate a dew heater into the holder frame. So I effectively get 4 features. I have seen the flip-flats, but wanted to keep the mechanics simple and not have to spend £300-£600 on a solution for all 4 features. Is it mad? Have I missed something obvious? It would be a little 28BYJ motor running off an Arduino nano or similar and an EL panel for the flats. Not sure how I would read the current position yet but sure that wouldnt be too tricky.

Have I missed a reasonably priced solution for this? Should I be considering a linear slide mechanism instead?

Ideas welcomed as im sleep deprived ?

Aim is to 3D print it so it could be made for any size. But primarily its designed to fit over the dew shield of the TS65Q

 

[Gina]

Looks alright to me.  That little stepper motor should do the job nicely.  You just need to work out w many steps to use.

[Dr_Ju_ju]

Are you thinking of putting all the control as well as the motor at the ota end ?  If so, the EL panel power supply usually needs 12v to drive its inverter, so you need to make allowances for the extra cables etc.

I'd also recommend some way to enable\disable the panel as the inverter can be quite noisy electrically, and may interfere with your other equipment.

And if you use some form of remote\auto-focuser (e.g. https://sourceforge.net/projects/arduinoascomfocuserpro2diy/ etc.) then the Bhatinov mask may not be required....

[upahill]

22 minutes ago, Gina said:

Looks alright to me.  That little stepper motor should do the job nicely.  You just need to work out w many steps to use.

Working on a method for detecting position cheaply. Which would mean it could rotate until it finds the place it should be then stop. I could calculate the steps and drive it but want to know it can work it out for itself too incase something shifts. Effectively parking with the cover over.

6 minutes ago, Dr_Ju_ju said:

Are you thinking of putting all the control as well as the motor at the ota end ?  If so, the EL panel power supply usually needs 12v to drive its inverter, so you need to make allowances for the extra cables etc.

I'd also recommend some way to enable\disable the panel as the inverter can be quite noisy electrically, and may interfere with your other equipment.

And if you use some form of remote\auto-focuser (e.g. https://sourceforge.net/projects/arduinoascomfocuserpro2diy/ etc.) then the Bhatinov mask may not be required....

I was thinking USB & 12v would run to the end of the OTA, so everything would be driven there. The panel will need to be enabled disabled by the arduino as its a combined cover for darks. How ill integrate that with APT/Ascom is beyond me at the moment but must be possible.

I was going to motorise the focuser eventually as well, and just use the bhatinov for manual changes. Im pretty sure APT has a focusing tool that measures FWHM that is supposed to be quite good but cant test until i motorise the focuser.

[Dr_Ju_ju]

I mostly use SGPro, and together with the focuser I linked to (granted you have to build it yourself), it works a treat, as Robert Brown, author, has also written an Ascom driver. It even works under Linux\Indilib\EKOS etc.

I have APT, but not tried it yet, maybe later on today as the skies are forecast to be clear again.....

[upahill]

2 minutes ago, Dr_Ju_ju said:

I mostly use SGPro, and together with the focuser I linked to (granted you have to build it yourself), it works a treat, as Robert Brown, author, has also written an Ascom driver. It even works under Linux\Indilib\EKOS etc.

I have APT, but not tried it yet, maybe later on today as the skies are forecast to be clear again.....

Have heard good things about SGPro - I went for APT as the learning curve seemed a little less steep and I fell in love with the plate solving goto etc. I haven't tried SGPro yet but probably should.

Im going to look into that project you linked too a little more, if it can be driven with ASCOM then APT will support it for focusing too - doing away with the bhat mask would simplify things for sure.

[upahill]

10 hours ago, Dr_Ju_ju said:

I mostly use SGPro, and together with the focuser I linked to (granted you have to build it yourself), it works a treat, as Robert Brown, author, has also written an Ascom driver.

Did you build one of these yourself? I just priced the components on eBay and its £98.49 before the PCB, including motor. Not too worried about the PCB as I can build it on vero board.

Granted thats because its all coming from different sellers so theres a lot of postage built in there - but even mouser/rs/element14 the pack sizes are killing me. Where did you source your components?

[kbrown]

I like your idea. Are you thinking of this as a permanent fixture on the OTA? If so, then weight considerations might be useful as it most likely with throw off the balance.

[Dr_Ju_ju]

 

2 hours ago, upahill said:

Did you build one of these yourself? I just priced the components on eBay and its £98.49 before the PCB, including motor. Not too worried about the PCB as I can build it on vero board.

Granted thats because its all coming from different sellers so theres a lot of postage built in there - but even mouser/rs/element14 the pack sizes are killing me. Where did you source your components?

I'm not sure how you arrived at that cost, as mine cost a lot less, including my own design PCB's, but I also have loads of components left over from my days @ the BBC. 

Most, if not all, of the components can be sourced on eBay @ zero shipping costs, the most expensive part being the stepper motor. I use these (https://www.ebay.co.uk/itm/27-1-Planetary-Gearbox-Nema-17-Stepper-Motor-1-68A-for-DIY-CNC-Robot-3D-Printer/121683241474?epid=1845687458&hash=item1c54e2ea02:g:x3sAAOSwjVVVji7p). I use cheap Hammond enclosures for the PCB and (optional) display, the motor mounting bracket, I printed, or made from some aluminium angle\sheet.

Total cost approx. £40~50\each, but I also made a batch of 5, which also reduced the cost. 

[skybadger]

You don't need the elp , you can use leds or pea bulbs. Set them back from the end flap by the radius of the tube to achieve a very flat illuminated field. Might reduce costs further. 

[upahill]

Most of the components are in for a myfocuserpro2, which will be added to my briefcase pack design, along with the dew controller by the same author.

This leaves flats/dark cover as the only requirement now so going to work on a more compact design.

[upahill]

After giving it some more thought and ordering the components for the myfocuserpro2 I have come up with a revised design. I have 3D printed a few iterations to get past tolerance issues etc and the EL panel I ordered fits perfectly inside the latest print, as does the 100mm disc of led difusing acrylic. This will be bluetooth/arduino controlled for raising and lowering the flap.

Im still not sure how I will do positioning - I have two pin holes in the body which I can wire to a open switch on the arduino - then when the flap is lowered enough a metal plate will complete the circuit. I wanted something a bit more elegant but this will do for this version.

Ill get some photos of the finished product once I get this hectic weekend out of the way and can work on it a little more.

Ill print a second one with a slightly larger aperature as a cover only for the guidescope.

 

[Gina]

Hall switches and little magnets can be useful for detecting position - something I've often done.

[upahill]

12 hours ago, Gina said:

Hall switches and little magnets can be useful for detecting position - something I've often done.

I havent used one before so will need to get hold of one and experiment with trigger distances etc, then integrate it into the body.

The belt distance worked out at exactly a 51 tooth GT2 belt, which is a convenient size and ready to order so getting one of those dispatched to save me making a belt. HC-05 module also arrived so if I can do this over bluetooth serial with an Ard Nano that would be great for integrating as a script in APT and cutting down on some extra wires.

[upahill]

Belt arrived and was too short. Must have got my calculations wrong somewhere along the line - but in all honesty I wasn't happy with the 3th printed prototype anyway.

I decided to take the opportunity to redo some of the elements of the design, namely putting a small push switch in the bottom of the OTA frame to signal when the flap is closed fully. I also wanted to beef up the swivel mechanics as it was just too... floppy... I'm now going with some teeny tiny bearings and a 5mm bolt to prevent having to drill out the bores on the pulleys. A third leg should help reinforce the hinge too as well as act as a mechanical stop.

I considered adding another sensor or switch into the top of the mount to determine when it was fully open but I think im just going to do it using a known number of steps. Eg, close until button detected, then open x number of steps.

All wires will go to a control box that will be strapped to the mount, this will then either be fed with just 12v and use bluetooth for comms or have a USB lead as well (depends how well my tests with the HC-05 module go)

Some renders until I can get round to getting the printer set up again (may not be allowed until after xmas now )

[upahill]

Well having nothing but issues. Dragged the printer back out of xmas storage and its showing off. Missing layers and generally rubbish quality so struggling to get a good print. Slic3r is doing much better than Cura for supports but needs some refining to get a good finish (I may just fill, sand and paint for the final)

Tonights print has worked enough to test tolerances once more, and the final bits have been ordered for both the flaps and the focuser. New bolts and shims, and some bearings (which I have sized wrong so need to change in the final print). Also ordered some black PLA as grey isn't going to cut it for me on this I'll be building an extra (without the EL panel) for the guide scope too - no real reason to other than I can and if I ever did get an obsy set up it would be an automatic dust cover.

I built the myfocuserpro2 circuit on xmas eve and it powers up enough to test, going to build with a nema pg27 reluctantly as im concerned a nema14 wont hold the camera well enough and want the extra torque the planetary gearbox should give me. A few switches to arrive and I can print a project box and bracket for the motor.

If my maths is right (it rarely is) then the PG27 should give me 306 full steps in the CFZ which is way more than the recommended 10-20.

The MyFocuserPro2 has ASCOM support, so I assume I can integrate it into APT fairly easily. The flap will be a script of my own design though - so getting it working within the imaging plan is the next challenge in the back of my mind.

That missed layer has really annoyed me.

[Dr_Ju_ju]

If you've printed in PLA, you could try smoothing the finish with Acetone (I use cheapo Tesco, nail varnish remover).

As for slicer, try Prusa's edition @ https://www.prusa3d.com/slic3r-prusa-edition/ even though its targeted at their printers, but the profiles are easily configurable, I find it makes a better 'job' than Cura and even Simplify 3D.

[upahill]

2 hours ago, Dr_Ju_ju said:

If you've printed in PLA, you could try smoothing the finish with Acetone (I use cheapo Tesco, nail varnish remover).

As for slicer, try Prusa's edition @ https://www.prusa3d.com/slic3r-prusa-edition/ even though its targeted at their printers, but the profiles are easily configurable, I find it makes a better 'job' than Cura and even Simplify 3D.

Might give it a go, have tried acetone smoothing with ABS with impressive results but not PLA.

I will give the prusa edition a go. I think one of my biggest issues right now is needing to recalibrate for this filament, in particular the retraction and temps.

[upahill]

New roll of filament seems to have done the trick, along with tweaking some settings in Slic3r for how supports are generated.

I'm really hoping this is the final one - getting a bit bored of printing them. Next step is the flap which houses the EL panel, that's about to start printing now.

 

[upahill]

Fresh off the printer....

The tolerances are much better this time around. 10th time lucky I guess.

Just need to wait for the hardware to arrive now and I can start putting it together.

[upahill]

Shims, bearings and washers in - but still not happy. The flap mechanism works albeit a little stiff.

The issue is around the motor. Positioning it carefully in cad, with accurate models just hasn't translated into real life and the belt is sloppy. Tighten it up and its pulling the flap at an angle - realistically the hinge points are the wrong way round and the tube ring should have the outside support on it I think. The 28BYJ motor is small and compact but my mounting options are limited with the silly little tabs - I really need slots so that the position is adjustable but that means turning the motor through 90 degrees at least adding to the height.

Thinking this might be a back to the drawing board kind of job.

On a more positive note I finished soldering up the MyFocuserPro2 board and testing that. It seems to be working on larger moves although single stepping with the buttons makes the motor jump a bit too aggressively. The PG27 motor gives me plenty of steps in the critical focus zone though. 92 micron focus zone, 3.58 microns per step. So around 25 steps.

The mount bolts in to the focus lock thread underneath, and into the threads for the finder mount. So its nice and secure, hugging the tube. Motor is connected to a DB9 which will go to the control box that is currently printing as I type. The box is only temporary until I build my control briefcase which will house everything.

Disconnecting is relatively quick as the whole assembly can just slide off once the coupler is loosened, allowing a quick switch back to manual focusing (although this can be done with the push buttons too on the controller)

My 3D printer heat bed decided to let out some of its magic smoke today so trialing cold bed printing before I can continue.

[upahill]

Well thats the printer dead, so yet another delay on all these projects and more money down the drain

 

[upahill]

I've been a bit lost with projects lately. I had to put everything on hold as I had the opportunity to build some new toys that will help with future projects (and a bit of side income hopefully)

Have spent the last couple of months building a 4'x4' CNC router and repairing a Laser cutter. Hopefully these two tools will help fund the astro addiction and build some more projects. It has unfortunately eaten into the time I had alloted for the rest of my projects and observing/imaging (not that the weather has been any good anyway.)

A new 220v silicone heating element arrived from China which has got the 3D printer working perfectly now. Bed heats up in 30 seconds and the SSR keeps it stable beautifully. Getting excellent prints now but its mostly churning out parts for the new toys.

Will be fun being able to cut / engrave more parts for stuff though

[skybadger]

Was the CdC router a box of parts or did you make it all ? .

How deep a cut can you make on the various materials ?

Looks very promising.

 

[upahill]

13 hours ago, skybadger said:

Was the CdC router a box of parts or did you make it all ? .

How deep a cut can you make on the various materials ?

Looks very promising.

 

Its a standard design called the Ox CNC, it can be bought as a kit, but I sourced the components separately to make a few mods and save a few quid. The biggest mod being a 2.2kw watercooled spindle which should be a bit quieter than the usual solution of strapping a router to it. It should be fine with cutting through any thickness MDF/Plywood etc. The bit will have a total travel of around 100mm.  It *should* do aluminum but very slowly.

My main reason for getting parts cut to my sizes was I wanted a 4'x4' cutting area. That's a little bigger than this design is suited for so im expecting to have to beef it up a little.

As for the laser, having proven the concept I just pulled the trigger on the next size up, which should be ok cutting through thin ply and, up to 10mm acrylic. The pics above were the smaller machine engraving into 9mm thick oak - it wont cut that without a lot of fiddling though.

Some of the projects im looking forward to using these for are:

• CNC'd foam inserts for suitcases to house scopes and mounts.
• CNC'd plywood frame to rebuild my dob.
• Custom Scope Rings / Dovetails etc.
• Laser etched PCB's for circuit boards.
• Tardis Observatory Project
• Various projects in the caravan/house.

It will be nice being able to go from solidworks design -> 3d printed prototypes -> cnc'd finished product in house. As well as help others out with their projects if needed.