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DIY ET-8 GOTO Mount

astrophotography eq mount
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#51 photo444

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Posted 02 January 2015 - 04:01 PM

You will see the result after stacking of 18 similar subs.  Thank!

 

No, the RA guide rate on OnStep was 0.5X.  1X made the mount oscillate. Things seem working. Thanks for many advises. :)


Edited by photo444, 02 January 2015 - 04:02 PM.


#52 photo444

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Posted 02 January 2015 - 05:16 PM

Below is a stacked (18 subs of 30sec ISO1600).

Attached Thumbnails

  • OrionM42Jan2-2015-400mm-9min-18x30sec-ISO1600D.png


#53 photo444

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Posted 02 January 2015 - 06:16 PM

Yet another exposure. M44 47 of 30sec  exposures at ISO1600 with Samsung NX300M and a 400mm Sigma APO lens. The moon was bright (two days before full moon) and the focus was not great.  Individual stars may reflect the 'dX-dY' plot shown in the post #48; The RMS radius is ~0.7 pixel so the angular size is ~12 arc-seconds which can be further reduced by increasing the focal length of the guide scope.

 

I am happy with the GOTO conversion of this CHEAP ET8 equatorial mount which I never had a good faith at all.  There still are a lot of room to improve but it can be used by AP lovers who seek a lot cheaper solutions.

Attached Thumbnails

  • M44-23min-1600-30secAS.png

Edited by photo444, 03 January 2015 - 06:25 PM.


#54 photo444

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Posted 03 January 2015 - 06:42 PM

When the weather gets better I will try a 400 mm lens for guiding, and use two cameras for picture taking: LN300 + F1.9 75mm f. l. and NX300M and a 200 mm ED lens.  I hope I can reduce the guiding noise somewhat. I may have to fight to get a new guiding condition, but now I have some place to start from.  Below is an example I got two years ago without guiding.  I had to throw away 80% of subs. I remember it was dark, clear and COLD night and all subs were taken manually in the brutal cold.  With fore mentioned improvements I can aim a better quality with guiding. 11 best frames were used for stacking.

Attached Thumbnails

  • Orion 11frames B C.jpg


#55 Starsareus

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Posted 03 January 2015 - 09:55 PM

Very interesting work. I'd like to see GOTO setups designed to handle heavier Classic GEM mounts(motor wise).  Seems commercial units are costly.



#56 photo444

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Posted 03 January 2015 - 11:19 PM

Very interesting work. I'd like to see GOTO setups designed to handle heavier Classic GEM mounts(motor wise).  Seems commercial units are costly.

What kind of mount do you have? Was it driven with some kind of synchronous motors?  I know hjd1964 has a G11 mount and he uses motors of 38 Oz-in rated torque.  I am using more powerful motor (92 Oz-in, MEMA17) because my mount has higher friction to turn.  I also have seen that HEQ5 type uses MENA 14 motors.  You can choose a variety of motors to suit for your need. One thing you have to consider is that the phase current.  This set up limits the current under 2 Amps which is hefty for most of motors. If you need higher torque use higher voltage - lower current combination.



#57 ssagerian

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Posted 04 January 2015 - 12:57 AM

Hello Everyone,

Howard and I have been working on an integrated version of the OnStep hardware. We started back the end of October and finished testing the Rev A boards middle of December.

The units worked well but we have a few improvements and possibly will  add a GPS module to the next revision of the board (Rev B).

I have started laying out the next rev of the board and expect to be done by the end of this next week, at which time I will send the design files off to have new  printed circuit boards (PCBs) made.

I am mentioning this to see if anyone is interested in getting a board made, if you are contact me off forum, at the end of next week (or when the design files are ready)  we will see how many people have indicated an interest, calculate a bill of material (BOM) cost based on our parts quantities and let everyone know what the costs will be, at that point, if we still have enough people, we will order board, parts and I will assemble (SMT) the boards and distribute them (the bom will have to have a shipping charge).  I have included a picture of the Rev A board. It has some improvements over the original concept onStep hardware, of course its one integrated pcb that mounts on an Ardiuno as a shield board, has the bluetooth connectivity,  it can micro-step the steppers, has over current protection (aka a fuse) , with a connector for a hall effect sensor (PEC) and a limit switch detect connector( not sure if the software supports the PEC or limit switch yet, but it has been tested).

I do not expect to get a lot of people responding, but if  ten or more people are interested, it will help defray the cost of the pcbs (some what) and we get discounted costs on parts . This wont be a cheap as buying everything your self and wiring it up (but of course it will be way more reliable and pretty ;-) ).

 

SteveOnStepRevA.jpg


Edited by ssagerian, 04 January 2015 - 01:09 AM.


#58 hjd1964

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Posted 04 January 2015 - 07:34 AM

Very interesting work. I'd like to see GOTO setups designed to handle heavier Classic GEM mounts(motor wise).  Seems commercial units are costly.

photo444's comments are spot on.  Also, be aware that the DRV8825 is not the only option.  Any step/dir type micro-stepping (or possibly even servo) driver should work, the TB6600 or DM860A aren't too expensive on ebay.  Some of these options should work with >1000 oz-in steppers (up to 8A/80V for the DM860A), though I've never had the need to try one.  Also, the ones I looked at don't seem to be able to switch micro-step modes on-the-fly.  So you'd be somewhat more limited in maximum goto speed depending on how fine an arc-sec/micro-step value you decide on when designing the system.



#59 photo444

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Posted 04 January 2015 - 10:41 AM

 

Very interesting work. I'd like to see GOTO setups designed to handle heavier Classic GEM mounts(motor wise).  Seems commercial units are costly.

photo444's comments are spot on.  Also, be aware that the DRV8825 is not the only option.  Any step/dir type micro-stepping (or possibly even servo) driver should work, the TB6600 or DM860A aren't too expensive on ebay.  Some of these options should work with >1000 oz-in steppers (up to 8A/80V for the DM860A), though I've never had the need to try one.  Also, the ones I looked at don't seem to be able to switch micro-step modes on-the-fly.  So you'd be somewhat more limited in maximum goto speed depending on how fine an arc-sec/micro-step value you decide on when designing the system.

 

I was thinking as a next project to interface between an Arduino Mega board and a TB6600 type board with OnStep software. It will require a minimum modification or none.  Then options of using wide range of stepper motors with high torque available in the industry opens up.  If you use stepper driver board that supports 5 (which is common nowadays on e-bay), you can add focusing, filter wheel, iris or zoom controls, etc.; the applications will be very exciting at very low coast!


Edited by photo444, 04 January 2015 - 10:44 AM.


#60 orlyandico

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Posted 04 January 2015 - 11:12 AM

Steve, sign me up for that shield.

 

I assume it will drive any bipolar stepper?  as for the bluetooth connectivity... will this work with SkySafari? or only with a laptop and ASCOM?

 

(SkySafari has a generic LX200 driver, so if OnStep supports the LX200 commands, it might work)



#61 hjd1964

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Posted 04 January 2015 - 12:41 PM

Steve, sign me up for that shield.

 

I assume it will drive any bipolar stepper?  as for the bluetooth connectivity... will this work with SkySafari? or only with a laptop and ASCOM?

 

(SkySafari has a generic LX200 driver, so if OnStep supports the LX200 commands, it might work)

OnStep supports both Serial0 and Serial1 on the the Mega2560.  In this case, Serial0 is tied to the USB and Serial1 is tied to the BT.  The command channels are identical and support an expanded LX200 compatible protocol.  I use an older version of SkySafari which functions fine, I assume that more recent versions function too.  GPS support is limited to grabbing the PPS signal as a precision time source, which isn't really necessary if you use a Mega2560 "clone" with an XO (ebay it.)  For this shield, and in general, the Dev branch on GitHub is best at this point.



#62 orlyandico

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Posted 04 January 2015 - 12:45 PM

Ahh.. the ebay clones.  Yup I have those.  Why the official Arduino's chose to use ceramic resonators is beyond me.

 

Would a Maxkit 32 work as well?



#63 hjd1964

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Posted 04 January 2015 - 01:52 PM

Chipkit Max32 isn't supported.  I see that it has Arduino compatible libraries and so could probably be persuaded into working without too much trouble.



#64 photo444

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Posted 06 January 2015 - 07:49 AM

I had a 'brief' window of clear sky last night, so I tested 400mm guide scope vs previous 75mm scope. Star image was sharper as you see in the picture which was taken under sky light of 1 day old full moon.  Arc seconds per pixel is now 3 (16 before), nearly 5 times improvement. The picture was taken with 200mm lens and cropped 100%. 

 

The guiding error with 75mm scope was about 1pixel RMS (16.2 arc seconds) but now with a 400mm scope it is about 1.5 pixel RMS (3 as/pixel times 1.5 pixel = 4.5 as).  It is about 3 fold improvement.  

 

I am thinking to use 400mm scope with a SUPER HAD 1/3" camera for guiding and the LN300 for EAA with other optics for example a lensless schmidt camera using 6"F3.3 plus a 0.5x reducer. 

 

Another path will be split the video from LN300 for guiding and EAA.  I may have to give up on-board image processing for this case.  Or buy a DSO-1 for EAA.   

Attached Thumbnails

  • M44 1-5-2015 200mm Crop 100p.jpg

Edited by photo444, 06 January 2015 - 10:13 AM.


#65 hjd1964

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Posted 06 January 2015 - 03:10 PM

Steve, sign me up for that shield.

 

I assume it will drive any bipolar stepper?  as for the bluetooth connectivity... will this work with SkySafari? or only with a laptop and ASCOM?

 

(SkySafari has a generic LX200 driver, so if OnStep supports the LX200 commands, it might work)

I didn't mention that this shield is indeed for bipolar steppers (and unipolar steppers in bipolar mode.)  The DRV8825 is rated for 8.2-45V @ a peak current of 2.5A, they can drive a fairly large stepper especially when running at 24 or 36 volts.  Also, this board is wired so the Mega2560 can control the micro-stepping mode & enable lines of each DRV8825 and It can read the driver fault lines too.



#66 ssagerian

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Posted 13 January 2015 - 12:19 AM

Hello Everyone,

I have finally finished the PCB layout and BOM for the Rev B version of the integrated OnStep Board.

Here are the costs based on 10 units.

 

Parts for 10 Boards  $450 (includes $10 shipping to my house, not shown on screen shot below)..

PCBs 10                    $105

Headers                     $  47

Total for 10                 $602

 

Split 10 ways of course is $60.20 US That includes a completely assembled and tested  OnStep Arduino  Mega Shield  board, as seen above (only the improved Rev B).

That does not include shipping to your home, nor does it include anything else (no stepper motors, no MEGA Arduino,  no power supply).

I am going to order boards tomorrow but will hold off ordering parts until the end of the week 12/16. if you are IN, send me a confirmation (OFF FORUM) irregardless if you sent me a earlier note.

I guess I will use my paypal account so you will need to  send $60.20, I will hold the money until the 16th, if we get 10 people great, if not, I will refund your money.

I will include some screen shots of the prices as revealed to me by the various sites I use (digikey, ebay and seeed).

 

The board does not have a GPS but I have started on a second shield for that option.

 

 

 

 

 

 

 

Attached Thumbnails

  • connector_estimates.PNG
  • digikey.PNG
  • pcb_estimate.PNG
  • boardlayoutRevB.PNG


#67 photo444

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Posted 13 January 2015 - 12:02 PM

Steve,

 

It's great work! I will sign up for one unit. Hope more will sign up soon.

I know very well by now that you cannot beat the cost $60.20 if you are going to build from scratch.  And another important thing is that IT WORKS GREAT!

 

Keep up the good work!

 

Paul



#68 hjd1964

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Posted 14 January 2015 - 01:43 PM

Just for fun, two more images made with my other OnStep controlled mount, a G11.  Taken with a 10"F/4 Newtonian and Quantix Photometrics 6303e camera.
 
C/2014 Q2 (Lovejoy) From 2015-1-14, 00:38 UT.   This was 2x2 binned mode.  A single three minute exposure unguided:
lovejoy.jpg
 
M31/etc. From 2015-1-14,01:09 UT.  Cropped down upper right portion of frame, no binning.  Registered and stacked from twenty exposures of 2 minute length, guided in PHD2 (no rejected frames):

m31_1_13_2014_upper_right_crop.jpg



#69 photo444

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Posted 15 January 2015 - 07:58 AM

Howard, 

 

They are beautifully captured. Thank for sharing.

I have been busy setting up EAA with LN300 lately, because the mount I have cannot handle heavier scope.

 

Paul



#70 ssagerian

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Posted 20 January 2015 - 01:33 PM

PCBs for the OnStep boards have been ordered and should arrive in about 5-15 days (most likely the later). I will be ordering parts shortly. Once the parts and boards arrive it takes about 5 days for me to SMT assemble and test (sorry about that day job gets in the way)

I will keep you posted..



#71 photo444

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Posted 24 January 2015 - 03:30 PM

Steve,

 

I am looking forward to receive it.

 

Thanks,

Paul



#72 ssagerian

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Posted 27 January 2015 - 05:21 AM

Hello Everyone,

a short information update, the bare  boards shipped yesterday. They should arrive in about a week to ten days.



#73 ssagerian

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Posted 27 January 2015 - 02:34 PM

Additional update..The digikey parts order has been placed and those parts should be arriving friday or monday. I have not yet ordered the thru hole connectors from ebay..I will do that today as well.

Steve



#74 photo444

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Posted 28 January 2015 - 01:31 PM

Steve,

 

Thank you for your updates.

 

Does the board can accept 24V instead of 12V?

 

Paul



#75 ssagerian

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Posted 28 January 2015 - 01:42 PM

Paul,

Ive used components that would allow the board to run to the chips rated voltage 45VDC, we haven't tested it at that voltage but I am comfortable with say it will work at 24V..




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