Thalestris24

4 minutes ago, vlaiv said:

Well - I don't really count my time or amount of money I spent developing it.

Since I plan to release specs to general public - it's more "the budget" needed to complete the project or BOM if you like.

I'm really developing this so that anyone who has 3d printer or access to one - can build themselves working star tracker that they can use for DSLR+lens or smart phone astrophotography.

Sort of 21st century barn door tracker kind of thing, but instead of going to "dad's workshop" to whip up some sort of contraption out of wood and scrap metal - one would do few clicks online to get needed goods and then its 3d printing and soldering time

 

Very altruistic of you! Maybe you could offer a 'deluxe' version too? I've not done any calculations but wondering whether it could be possible to simplify it with a direct drive rather than gearing? If it's just a camera and lens you wouldn't need the torque that you'd presumably get from gearing? Just thinking out loud...

Louise

46 minutes ago, vlaiv said:

That is way more expensive and powerful than it needs to be.

DRV8828 can be purchased for as low as 1-2 euro a piece.

If one wants 128 or even 256 micro steps then something like TMC2208/2209 is just a bit more expensive - ~4 euro a piece.

https://www.ebay.co.uk/itm/275420178213?hash=item4020526725:g:kYAAAOSw63Ni9ggA&amdata=enc%3AAQAHAAAAwN5a%2FWvx2BoXK9nD1CsIBwct65P6VAgZjY98Jn9lnotGFDdDLTAlBVbriWCM%2B2Ex4U3PxT2O7o6wxaNbW5gby2rQIMLH%2BpUE7ttf52hj%2B9BNovnDB0fnWBnGpUZFDI%2BZO3AZjKu5XDum%2BN95LDvoVvUll0xQqQK%2B0F63X2ErC41%2FO3YLdKkQvw3dJuPAXujnnwwZeL7znoBIF%2BaTF1n5wQfOJpsB2g5Cdu9fXVeXC98M5u3OmTeBWwns%2BPDZ3ZU8QQ%3D%3D|tkp%3ABk9SR77x797aYQ

One can also save about 5 euro by using 1.8 degree over 0.9 degree stepper.

If I'm going to aim to get it done within 50 euro budget - every little saving counts.

 

Oh ok. 50 Euro seems a bit low - especially if you cost your own time spent on it! Not to mention current levels of inflation... It's all relative, I suppose  

Louise

21 minutes ago, vlaiv said:

Mostly to do with keeping the cost down and with simplicity.

There are two cheap / readily available drivers for stepper motors - A4988 and DRV8825.

Out of these two - DRV8825 supports 32 micro steps - A4988 supports only 16. On top of that DRV8825 is quite a bit less noisy in operation (not silent but not as noisy either).

I've also chosen stepper motor that is the cheapest of the bunch. There are nice smaller units (like Nema 8 ) - but they are often more expensive. Hence 1.8 degrees per step and not 0.9.

In final build, people will certainly be able to choose their components as most are drop in replacement - but I wanted to see what is the minimum budget that I could get by with.

 

Oh ok. Though 0.9 deg steppers aren't especially (more) expensive, at least not here in the UK NEMA17 Stepper Motors - Ooznest | Kits, Parts & Supplies

You can get 128 step controllers for not a huge amount e.g. New DC 12-50V 4A Stepper Motor Driver 128 Microstep 2-phase Controller | eBay or 

DM542 Stepper Motor Driver Controller DC 24-50V Nema 23 / 17 CNC 4.2a DM 542 NEW | eBay

It may be worth it as that's where all the magic is!

Anyway, good luck with the project  

Louise

Hi Vlaiv

Just doing a quick catchup on your development  Was wondering why you were limiting your design above  to 32 microsteps when 128 microsteps are possible and with a 0.9deg/turn motor? I'm sure there must be a good reason! Is it to do with holding current or precision? (I'm no expert on microstepping!)

Louise

7 hours ago, CharlieM said:

I'm clicking the links in this thread and getting nowhere. Louise, did you finally get your plate and if so, can you please tell me, with a link that works, where you got it from ? Thank you.

You have to buy them from jeulin: Radial Slot Tokens (jeulin.com)

Good luck!

My Ender 3 Pro v1 is still going strong! Just over 3 years old now. I had an issue a while ago when the filament was having problems feeding into the extruder. I couldn't figure it out - thought there must be a blockage or something. It turned out that the filament was snagging around the vertical lead screw... I couldn't see the problem from the front. Not sure how it happened - probably because I'd been keeping the filament reel in a zip-lock bag and sat on the bed.  When I returned the spool to its holder, I must have got it snagged. As soon as I re-routed the filament the problem was solved. I still use the brass nozzles with PLA but they do tend to gum up after a while, so I just put a new one on. I do use a teflon insert in the hot end. Occasionally the hot-end inlet nut comes loose. I also noticed a problem with the x-gantry becoming loose - apparently on the right-hand side. However, the fix was to undo the top section, lift the x-gantry off, and tighten the two allen-key bolts which fasten it to the stepper-motor end. I use a metal feeler gauge (0.15) for levelling - nice and precise!  

Louise

ps my hair has mostly turned white now - nothing to do with 3D printing, just old age!

1 hour ago, vlaiv said:

I'm afraid not.

I've taken on too much DIY projects (finishing enclosure for 3d printer and modding it) and on top of that we are finishing top floor of the house (floors, doors, electrical appliances) so I'm all over the place at the moment and most of side projects have been put on hold last few weeks.

Hopefully, I'll have more time by the end of November to get it going again.

Ahh busy, busy, busy! No worries - take care and all the best!

Louise

Any news / progress on the star tracker, Vlaiv?

Louise

Looks like I'll be able to continue with the Fusion 360 after all  It says the personal license has a limitation of '10 documents' which seemed a bit restrictive. But when I asked, they clarified and explained it just means you can only have 10 designs open at a time. Since I mostly only work on one or two things at a time, that's not a problem. It's just coming up to 3 years since I first bought a 3D printer and started with the Education Fusion 360 License - both items just to make the Lowspec spectrometer! I've found having a 3D printer so useful for other things, especially as I'm a compulsive tinkerer!

Louise

20 minutes ago, vlaiv said:

I've already settled on type of reduction for this star tracker.

It will be either split ring planetary gear type or cycloidal drive.

These can both be made very compact.

Worm gear above is meant only for fine/precise alt azimuth adjustment of polar wedge for star tracker.

Actual drives that will move the tracker will be one of these types:

https://www.youtube.com/watch?v=aTiBB2n-pNQ

or

https://www.youtube.com/watch?v=-VtbSvVxaFA

Reduction needed is order of 200:1

This can be easily calculated depending on needed arcsecond per micro step precision. I went with something like ~1"/micro step for star tracker (AZGti has 0.6"/micro step for example).

360 x 60 x 60 = 1296000 arc seconds in single revolution

200 steps per revolution for 1.8 degree stepper, and if we say use 32 micro stepping we get 6400 micro steps per revolution.

1296000/6400 = 202.5

So we need exactly 202.5:1 if we want to get 1"/micro step

200:1 is easily achieved in two step reduction - 1:10 x 1:20 for example, or even in single stage for split ring compound planetary gear thingy.

For full tracker (AzGTI type device) - I'd go with cycloidal drive + 1:7 belt as final stage to offset motor shaft from output shaft, so cycloidal drive would need to be something like 1:30 which is easily achieved.

I wish I could print so precisely! All the gear ratios and cycloidal drives are beyond me! Looking forward to seeing the finished article though!

Louise 

1 hour ago, pipnina said:

Ah fair point.

I found some brass worm gear sets on ebay for pretty cheap. But they are only 1:60 ratio so they'd probably need to be "doubled up" in some way as big mounts have several hundred to 1 gear ratios.

https://www.ebay.co.uk/itm/203162743596

I guess 3D-printed large gear attached to the worm and a smaller 3D-printed gear on the motor, with a belt between them would be pretty cheap in component parts to boost the ratio up to 200:1 or so?

Belts are pretty cheap from the rowan set so maybe it could work? https://www.firstlightoptics.com/rowan-astronomy-mounts/rowan-astronomy-sky-watcher-heq5-pro-spare-belt.html

To be honest your idea makes a lot of sense.

Yeah a Rowan belt setup is quite good - works great on my HEQ5 Pro  But I was thinking of something different which I'm now not sure if it could easily be done - it was just a thought that flitted across my mind. I'm probably overcomplicating things! I have one of these focus rails that I bought a few years ago. As you can see, they don't come cheap but probably much cheaper if you just buy individual generic components. The magic is in the usb controller and software which allows a high precision of control (microstepping). But... It's a linear rail and I'm not sure if it would easily translate into a worm gear type setup. You can get less precise, but very similar, parts as spares for 3D printers e.g. Lead Screw on Ebay. However, thinking about it, being linear they can't easily be used in the same way as a normal gear ratio rotating system - unfortunately.  They could maybe be used for a precision 'barn door' type setup. When I first started in astronomy, I did consider making a barn door thingy but decided an equatorial mount would be an awful lot better - once I could afford one! But then I didn't know about precision lead screws and stuff. There's always more than one way to crack a nut!

Louise

3 minutes ago, vlaiv said:

Hi Louise

I sorted moisture with one of those Ikea samla cases with silica beads inside and little hygrometer to tell me relative humidity (it sits at 10% which I believe is minimum for device). There I store filament when not in use. I also used food dehydrator initially  without any modifications for few hours and it really helped to get things started in right direction.

In fact that set me off to whole new direction with my 3d printing / modding. I'm in the middle of Ikea lack enclosure build. I added banana pi for running Klipper firmware (made mistake of going with Banana pi M4 - which is not well supported as far as OSes go - so I ended up using Ubuntu 16.04 and upgrading it to 20.04 just to be able to install all that is needed for klipper + fluidd).

Right now I'm finishing electronics enclosure for Banana PI + step down voltage converter and will move on to print electronics enclosure for small MeanWell PSU that will power BPI, air filter fan and LED strip for lighting

above is banana pi enclosure with mounting system being ready to install on outside of enclosure

For that reason, star tracker project is a bit on a hold, but will continue soon.

Not sure I want to use any sort of metal gears if they are not very cheap and easily accessible everywhere. Aim of the project is to be able to print star tracker almost anywhere in the world (like no need to import things - only purchase locally in hardware store).

As far as FreeCad goes - I find it very useful, or rather - I leaned to use it properly after all this time and now I don't even think about it. Sure, there are always some new things to be learned - but it is quite powerful tool. Just few days ago I leaned how easy it is to create technical drawings from 3d designed objects:

Piece of cake really.

As far as threads go - I do my own threads and it is easy in FreeCad, but maybe a bit involved as you need to draw your own profile.

I simply draw profile of single tooth - for either nut or bolt and then do helix revolution of it - either additive if bolt or subtractive if nut. Metric threads are really easy to make - 60 triangle is base. I use this page whenever in doubt:

https://en.wikipedia.org/wiki/ISO_metric_screw_thread

I don't like tool that is offered for threads in FreeCad as it uses some sort of Bezier curves and threads end up not looking good.

With ziplock plastic bags it's simple as you can see the beads and if they've darkened! In practice, small amounts of moisture in filament aren't critical. I have some black pla filament which I've had on the printer for quite a few months and it's still ok. I will put it in a bag for a few days soon though!  

Louise

1 minute ago, pipnina said:

I couldn't find a spare part listing for the main worm-driven gear, but the motor-to-worm gear train replacement parts are about €35 and a worm gear replacement is €45 for EQ5 tier mounts! They are made of brass and low volume however so not surprising that they are expensive.

Oh ok, I was thinking more in terms of generic parts that could be made use of. As I've never looked, I accept you're probably right! At the same time I intuitively feel someone must have made a star tracker from scratch before somewhere.... There are some projects on Thingiverse but, yeah, all also seem to use printed gears. However, presumably the aim is to control the tracker at a sidereal rate so that could be controlled by an Arduino-type processor, stepper motor and the control pulses adjusted for whatever the worm/gear/stepper motor combo allows? I'm just thinking out loud - I've probably missed something obvious! I'm so out of touch with astro things these days! I do have a motorised rail which I use for a microscope and which allows microsteps in the micrometer range.

Louise 

Cool project, Vlaiv! Might metal gears be better and more rugged? I'd have thought the Star Adventurer, or similar, gears would be easily obtainable? (Though I admit I've no idea really.) Then you'd just need to make the housing/add a motor etc.?

Re: Filament absorbing moisture. If you get some large ziplock plastic bags (47 x 33 cm) you can store/dry filament by including a few handfuls of silica beads in a small porous/mesh bag. I find I can quickly and easily dry the beads for re-use in my microwave oven . 

How are you finding FreeCAD? My educational Fusion 360 is about to expire so I might switch to FreeCAD. I'm not sure what I might lose by using the hobbyist Fusion 360 instead - especially with things like threads and custom threads. I suspect it's not easy to create T2 threads in FreeCAD but I'll have a look.

Cheers

Louise

1 minute ago, chemistorge said:

Hi Sorry, I attached the github html download not the correct xml file.

 

Here is the correct XML file.AstroThreads.xml

Ah - that would explain it! I find I have to put in my own custom values in order to get T2 threads to work on my Ender 3 Pro v1. I'll compare my values to yours!

Thanks

Louise

On 20/08/2022 at 13:41, chemistorge said:

just to add my experience: I have printed threads, 1.25", 2" and M42. In my experience internal threads tend to shrink a little making them tight. To alleviate this I created an 8G tolerance for internal threads to account for this.  

I also print if possible with the threads around the z-axis with a 0.1 mm layer height.

 

I have included  my fusion 360 thread file with 8G tolerances

Astronomy Fusion 360 Custom Threads.xml 293.21 kB · 6 downloads

Hi

I was interested to see what values you've used for the astro threads but have not managed to read your .xml It throws up an error in Edge and the downloaded file isn't easily readable in Notepad++ which I normally use for xml files like the AstroISOmetric one. Any ideas?

Thanks

Louise

On 28/07/2022 at 20:07, iapa said:

Barely acceptable, but here's my 1st light Image07_DBE_ABE.tifwith some (mostly) unused kit.

• Esprit ED80 Pro and flattener purchased on SGL in 2021 - 1st use
• ASIAir Pro- 1st use
• ASI 294MC pro - 1st use
• stock AVX (6yo) - stored outdoor for past 3? years unde

Image details

• unguided
• c 90 x 30s light
• 30 x bias @ 1mS
• 40 x dark@ 30S
• 0 x flats
• 0 x dark flats

Image07_DBE_ABE.tif 133.85 MB · 10 downloads

Hiya

i took the liberty of doing a quick auto stretch.... Would benefit a lot from flats 

Louise

1 hour ago, PeterCPC said:

Sadly not Louise.

 

Thanks for the reply, Peter. I had a feeling all was not well and I think she was a bit older than me. Sad times.

Louise

On 23/01/2022 at 19:49, Gina said:

Orion's Sword in Narrow Band

Captured on 20th January 2022 with my triple imaging rig and processed in PixInsight.  HSO.

Ha - 29x5m = 2h25m   ASI 294MM camera with Ha 3nm Astrodon filter and 200mm Asahi Super Takumar lens
OIII - 8x15m = 2h         ASI 1600MM-C camera with OIII 3nm Astrodon filter and 200mm Asahi Super Takumar lens
SII - 6x20m = 2h          ASI 1600MM-C camera with SII 3nm Astrodon filter and 200mm Asahi Super Takumar lens
Guider                          ASI 178MM camera and 55mm Asahi Super Takumar lens stopped down to f4

Capture systems Raspberry Pi 4B running Astroberry Server x 3.  Connected via Ethernet to tower computer running KStars/Ekos. 

Are you still around, Gina?

Louise

Not sure if he was any relation to James Webb but David Webb was Jason Bourne's real name

Louise

1 hour ago, Thalestris24 said:

Hmm... I don't think that IR is an issue, at least it wasn't with the original Lowspec that I printed. Even if it was, I'm sure you could spray or coat the outside with something opaque to IR. What symptoms do you have with the printer?

Louise

The attached paper suggests that black PLA is pretty much opaque to near IR

3D_OpticalTransmittance.pdf

17 minutes ago, SteveBz said:

Back home now 🙂

Paul says PLA is transparent at IR wavelegths that's why he prefers it.

My printer is refusing to do anything at the moment, I need my friend to come over and beat it into submission.

 

Hmm... I don't think that IR is an issue, at least it wasn't with the original Lowspec that I printed. Even if it was, I'm sure you could spray or coat the outside with something opaque to IR. What symptoms do you have with the printer?

Louise

20 minutes ago, SteveBz said:

Hi Louise,

@Paul Gerlach does come from time to time and so he'll probably see this eventually.  He's also following this thread, so if he scrolls back three he'll see my question.

The reason is that he recommended that brand of ABS, so I presume he can tell me what parameters to use.

Kind regards

Steve.

OK, tho I don't see any need for ABS over PLA but it's up to you! I seem to remember (3yrs ago) that Paul had a more sophisticated printer then, at least...

Louise

2 hours ago, SteveBz said:

Hi Paul,

I bought this, but I'm having serious problems with printing it.  Can I ask you for some tips please?  I have an Ender-3 printer.  Specifically, I'd like to know:

- What temperature do you use on the extruder nozzle?  I'm using 260 C

- What temperature do you use on the bed? I'm using 80C. 

- What nozzle do you use? Mine is stainless steel and 0.4 mm.

- How do you assure adhesion to the bed? I'm using hairspray.

- What settings should I use in Cura?  Eg Support, skirt, raft etc etc etc.

This project isn't for the faint hearted!  3D printing on its own is a new skill!

Thanks

Steve,

Am not sure how often Paul comes on here... Is there any reason you don't want to use PLA or PLA+ or PLA carbon fibre?

The carbon fibre one is supposed to be stronger, stiffer and lighter but prefers a hardened steel nozzle. 

Also, Cura is rather slow - I use Prusa Slicer which I find easy and pretty good https://github.com/prusa3d/PrusaSlicer/releases/tag/version_2.5.0-alpha2

- that's the latest release which I've not tried myself yet. (You just make a folder and 'extract all' into a subfolder then do a 'send to' desktop of the .exe file.

I think the first time you install, you select which printer(s) you are using it for i.e. Ender 3 and configure accordingly

Hth

Louise 

2 minutes ago, SteveBz said:

OK, so the same chip.  Is that Toucam?

No - Altair Astro