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JohnSadlerAstro

Those EQ5 Steppers

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Hi,

But I....I could do no other 😭! 2 years ago I bought a basic EQ5 with STEPPER MOTORS! 😱 And it was for A.P. I am now suffering for my stupidity and cheapskate-ness, through a 9 month long struggle with my setup which has left me mentally and physically exhausted…. :D 

So essentially the whole setup was dysfunctional since last new year. I've managed to fix everything else in it other than the autoguiding. The Dec backlash just seems to be too large to resolve. I've tried one way guiding, but the same thing happens everytime: the star moves either N or S, and then sits at about 2-4" out. The dec motor corrects for say 20 corrections, all the time the star doesn't move at all or continues to drift. Finally, the star moves back to the centre again and guiding continues within 2" for the few minutes. I've tried the backlash comp and it says I need about 50ms of compensation. as you can imagine, im a little sceptical. 😏

I'm running a 130P-DS and 1000d on board, I used to be able to get 3min subs with about a 60% success rate, but although ive kinda forgotten exactly how accurate the guiding was back then, I'm pretty sure its a good bit worse atm. I have a dream of imaging galaxies and that was just beginning to take off--so I'm determined this make me give up.

The RA motor graphs look like a scene from the Alps, but im pretty sure I can fix that with some worm tension.

Are there any alternatives to the steppers, or modifications I could do, that wouldn't cost too much? I have seen some DIY mods to the steppers, but there weren't any details about how they worked, and they seemed to need a machine shop to complete. 😐

I'd like to get the goto upgrade but its just too expensive, also I am planning to upgrade to a HEQ5 within the next few years. Unfortunately I am last year before uni and everything wants money, so no big buys anytime soon. :(

John

Edited by JohnSadlerAstro

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Good thing it has stepper motors. Question, how are motors driving the axes ?, I take it with Synta's cogged drives ? if so the replace with some toothed pulleys & a belt (they are cheap, on the bay) !!

Have a look through this thread, which has pictures of what I've done to mine.....

 As well as the above, it may well be worth stripping the mount down & cleaning\'tuning' it. There are videos on the tube describing the process...

After that comes the electronic drive system, I use an AstroEQ to PC interface ~ motor drive the mount, which works very well, but may be too expensive for you ?

 

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Hi,

Thanks for the reply--yes, they are connected with the standard cogs. My only concern is, surely a pulley/belt will mess up the gearing ratio? :confused1: It's really confusing, all the different gear and belt sizes and ratios. Your mount looks really nice with the mod on it, though. How well does it guide? There is an EQ mod for sale in classified, it may be a cobweb though! ;) 

I don't know if it was the same on your mount, but the steppers have a lot of play in them as well--I can turn their gear by something around 2 degrees. Quite a definite "tick, tock" noise when I turn it back and forth. I guess some higher quality steppers would remove this but although they might be cheap all the brackets and power connectors would be incompatible with the hand controller I have. :( 

John

Edited by JohnSadlerAstro

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3 minutes ago, JohnSadlerAstro said:

Hi,

Thanks for the reply--yes, they are connected with the standard cogs. My only concern is, surely a pulley/belt will mess up the gearing ratio? :confused1: 

I don't know if it was the same on your mount, but the steppers have a lot of play in them as well--I can turn their gear by something around 2 degrees. Quite a definite "tick, tock" noise when I turn it back and forth. I guess some higher quality steppers would remove this but although they might be cheap all the brackets and power connectors would be incompatible with the hand controller I have. :( 

John

That's normal for steppers, they typically will have 'cogs' at 1.8 degree intervals, but the driver should use microstepping to give a resolution 1/16 or 1/32 of this.

Have you adjusted the mesh of both the gear train AND the worm wheel on each axis?

Having the mount perfectly balanced will make things worse unless you have very little backlash, unbalancing particularly in DEC can help things.

What are you using to guide? If it's PHD2 you may need to experiment with the guide algorithms.

I found that the Lowpass2 algorithm appeared to work well, then went crazy just as you describe and I've got an HEQ5. The manual says "LowPass2 is a very conservative, high-impedance algorithm that may be a good choice for users with good seeing conditions and well-behaved mounts with little or no declination backlash." What was happening was any fail in guiding was setting off chaotic (in the mathematical sense) swings in DEC.

Can you share some guide logs (you do have these, all you need to do is download the viewer and grab some screenshots)

 

If I can get 5-minute subs on an EQ3 fitted with steppers out of old computer printers, I'm sure you can get this sorted.

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22 minutes ago, Stub Mandrel said:

That's normal for steppers, they typically will have 'cogs' at 1.8 degree intervals, but the driver should use microstepping to give a resolution 1/16 or 1/32 of this. 

Have you adjusted the mesh of both the gear train AND the worm wheel on each axis? 

Having the mount perfectly balanced will make things worse unless you have very little backlash, unbalancing particularly in DEC can help things. 

What are you using to guide? If it's PHD2 you may need to experiment with the guide algorithms.

I found that the Lowpass2 algorithm appeared to work well, then went crazy just as you describe and I've got an HEQ5. The manual says "LowPass2 is a very conservative, high-impedance algorithm that may be a good choice for users with good seeing conditions and well-behaved mounts with little or no declination backlash." What was happening was any fail in guiding was setting off chaotic (in the mathematical sense) swings in DEC. 

Can you share some guide logs (you do have these, all you need to do is download the viewer and grab some screenshots) 

If I can get 5-minute subs on an EQ3 fitted with steppers out of old computer printers, I'm sure you can get this sorted.

Hi,

Thank you for the encouragement.

I was using 'LowPass', which I was told was a "good" algorithms for Dec issues. 🤔

I have adjusted the tension of the worm multiple times, its very difficult to get the right balance between being too stiff and causing stiction and being too loose and getting bad backlash. I could try tightening it just a little more on both axes. 

This is a screenshot of a 10 min guide. Imo this is a single "unit" of the issue. You can see it drops back down again at the end ready to begin the cycle again. :( 

image.thumb.png.616a09f5e6c52b8afd2a3a45e8bc5629.png

John

Edited by JohnSadlerAstro

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I'm sure I'm having déjà vu, but its pretty easy to fix - you really need an AstroEQ and then some real steppers and belts...

IMG_0615.JPG

My brackets are of the extreme bodger variety however there is a nicely designed set on thingiverse to 3D print

https://www.thingiverse.com/thing:1833860

Most of the details you need are on AstroEQ's website but its pretty cheap/easy to get very high quality guiding out of an EQ5 ...

guiding.png

 

In terms of pricing - steppers belts and pulleys will be £25 and an AstroEQ built from a Mega2650 will be about £20, or depending on your electronics capability £35 to build a genuine AstroEQ using one of Tom's boards.

 

I'm planning to do some 3D printed brackets soon to tart mine up a bit - I'll print you a set once I have the files set up.

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1 hour ago, Dr_Ju_ju said:

As well as the above, it may well be worth stripping the mount down & cleaning\'tuning' it. There are videos on the tube describing the process...

I'd agree with that.  I have an older EQ5 with the goto motors, bought used, and it has never been great. 
Last week I bit the bullet and stripped it down to components, cleaned everything and regreased.  I got my first play with it last night and the differenvce is outstanding!  I guided perfectly for 5 minutes at a time and could have tried for more but the images were washed out with light pollution.

The picture is the Dec cog wheel as I started cleaning it.  I used wooden toothpicks to clear the (144) teeth - it can't damage the metal and I would have felt any scratches or rough spots.  I then used a toothbrush and Archoil AR4200 CLP Firearms Oil with soft cloths to finish the job.

One word of warning about that Archoil.  I'd used it based on a recomendation here or in another forum - can't remember.  It is a very effective lubricant!
The smooth face of the part in the photo is where the clutch grips when you tighten it.  I didn't clean the Archoil off these faces and now my clutches don't grip very well!  I'll probably need to strip it again to clean these faces 🙄

All the best

MichaelIMG_3424_Zoom.thumb.jpg.def494b6078b9d4054e1d8da56549fd2.jpg

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Hi,

The homemade stuff looks really daunting, but I guess I could work through it if I bought as much as possible of the parts..

I stripped down and regreased my mount in the summer holidays, I used this stuff:

https://www.halfords.com/motoring/engine-oils-fluids/grease/comma-multi-purpose-grease-tube 

I believe I used a toothbrush to clean most of the old grease out of the teeth.

EDIT: Perhaps using that was a mistake.

John

Edited by JohnSadlerAstro

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Just a quick entry here. I'm a massive fan of Superlube. It does a fantastic job.

 

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4 minutes ago, JohnSadlerAstro said:

@Synchronicity How much did you use? 

I'd like to get away with a 20ml sample tube or two from here ;)

https://www.powerenhancer.co.uk/archoil-ar4200-clp-firearms-oil-3247.html

John

I used a small amount from one 20mm tube, having bought 3 just in case!  PM me your address and I'll post one off to you.

Michael

Edited by Synchronicity
Typo

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4 hours ago, JohnSadlerAstro said:

I was using 'LowPass', which I was told was a "good" algorithms for Dec issues. 🤔

Fro me, Lowpass good, Lowpass2 bad 🙂

"Your mileage may vary"

 

I would suggest using a grease not oil; grease is ideal for this highload, low velocity application and also helps to damp movement which oil won't. Plus it will stay in place for years.

Edited by Stub Mandrel

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@JohnSadlerAstro just for info I'v just transformed appalling DEC guiding (zigzagging non stop between +/- 16") into 0.56" rms. All I did was move the OTA of my 150PL about 1" in the mount.

Don't despair, just experiment!

Edited by Stub Mandrel
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@Stub Mandrel The results are in:

I messed about a bit with the worms outside, I found that at 0.5x sidereal, the dec requires, drumroll please, 19 1200msec manual guide movements! :D

At this point I have two theories:

#1 the motor has somehow stripped some of its internal teeth, so its slipping. I'm not sure how to test this, really.

#2 the worms are messed up in a next level way.

My plan is to get the setup out tmrw in daytime when I can really see what im doing, put the guidecam into the main scope and zoom right in on something, then put a crosshair over the video feed. I should be able to watch for movements quite easily, so I can play around with manual guide and the worm settings as much as I like and just see what happens.

If the motor is stripped, my best move is just to start trying to collect together the parts needed for the mod. The main obstacle is that the Astro EQ controller is discontinued on the website. 😐 

John

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A new possibility:

The Dec gear and the cog on the end of the worm assembly weren't lined up well at all. I've filed down some washers and used them as shims to bring the two gears together perfectly flat, and it may have reduced the backlash quite a bit. I'm going to test with the camera and see if I can detect a change. Tonight looks clear, though, so I should be able to try then as well.

John

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On 28/09/2018 at 10:51, John78 said:

I'm sure I'm having déjà vu, but its pretty easy to fix - you really need an AstroEQ and then some real steppers and belts...

IMG_0615.JPG

My brackets are of the extreme bodger variety however there is a nicely designed set on thingiverse to 3D print

https://www.thingiverse.com/thing:1833860

Most of the details you need are on AstroEQ's website but its pretty cheap/easy to get very high quality guiding out of an EQ5 ...

guiding.png

 

In terms of pricing - steppers belts and pulleys will be £25 and an AstroEQ built from a Mega2650 will be about £20, or depending on your electronics capability £35 to build a genuine AstroEQ using one of Tom's boards.

 

I'm planning to do some 3D printed brackets soon to tart mine up a bit - I'll print you a set once I have the files set up.

Like this?

PS how many teeth on that big pully?

IMAG0278.jpg

Edited by jase1973
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Its 52T its too big to fit so required some adjustments with a dremel tool to get it clear of the mount.

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18 hours ago, John78 said:

Its 52T its too big to fit so required some adjustments with a dremel tool to get it clear of the mount.

 

18 hours ago, John78 said:

Its 52T its too big to fit so required some adjustments with a dremel tool to get it clear of the mount.

Much fettling? I put 40t on. But I got the wrong shaft size so need to get more. Worth it for the bigger ones?

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4 minutes ago, jase1973 said:

 

Much fettling? I put 40t on. But I got the wrong shaft size so need to get more. Worth it for the bigger ones?

Few mm off the body of the mount to get them clear - worth it because I had the pulleys already in my bits box, I didn't specifically choose them for increased resolution.

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