DIY Equatorial Mount

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Re: DIY Equatorial Mount

Postby Jerry » Thu May 08, 2014 12:04 am

I started on the frame that holds the main drive last night. I had the original piece the big harmonic drive mounted to as well as some of the aluminum for the base. It is all 1/2" aluminum. Finished up that part tonight. The plates have bores for bearings and curved slots for the angle adjustment. It will got up to 60degrees of tilt. I am still working out the design of the base section, I have got a good idea what I want to do, just not sure.

I might send some of the parts out for bead blasting and anodizing.

Side pieces and top before machining:

ImageTelescope mount parts by macona, on Flickr

Completed frame:

ImageTelescope mount parts by macona, on Flickr

Drive mounted in frame:

ImageTelescope mount parts by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Jerry » Thu May 15, 2014 10:43 pm

I got the parts back from anodizing today. I decided to go ahead and send out what I had done since I need to press in the bearings and once they are in I was worried I couldn't get them out. Cant anodize them with steel in them.

They came out pretty nice. I decided not to anodize the main drive, I didn't want to take it all apart. Some pics of it all together below.

The thing is getting pretty heavy. I am kind of thinking of getting a small trailer and mounting it to that. The trailer would have outriggers to level it and get it off the wheels.

Also need to start thinking about a polar scope. A polar scope makes alignment much easier. It attaches to the mount and you use Polaris to get the mount lined up.

I plan on making the base this mounts to this weekend. It will pivot on two taper bearings and then sit on thrust bearings for polar alignment.

ImageIMG_8565 by macona, on Flickr

ImageIMG_8563 by macona, on Flickr

ImageIMG_8560 by macona, on Flickr

ImageIMG_8559 by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Jerry » Wed May 28, 2014 2:29 am

Another batch of parts finished for the telescope. I have decided to just buy a saddle and dovetail kit from ADM, I dont want to mess with that.

Needed a piece of aluminum rod for the bearing spacer/axle. Couldn't find anything but I did have a piece of titanium, close enough...

ImageUntitled by macona, on Flickr

Making the spud that the base rotates around. I used some 17-4 TGP stainless I had left over from an old job years ago. Found an insert that would actually break chips with this stuff which just created tiny super hot little chips flying everywhere. Ouch!

I am using a large ball thrust bearing for support and a taper bearing on top of that. The spud ties it all together and also serves as what the fine adjust presses against. I single pointed 5/8-18 threads for a nylok to tighten up the bearings.

ImageUntitled by macona, on Flickr

This piece is the fine adjustment arm, two Vlier fixture screws will push on either side and allow it to move around it's axis. It is slit down the middle to clamp on the spud and can be loosened for rough alignment.

ImageUntitled by macona, on Flickr

ImageUntitled by macona, on Flickr

Everything ready for anodizing:

ImageLast batch of parts by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Jerry » Fri Jun 13, 2014 12:35 am

I got my parts back from anodizing today and assembled what I have so far.

I think I have created a monster.

I inserted the bearing cup into the base, a bit of a tight fit but it pressed into place and trimmed the spud to it's final length. I lubed up the two bearings with Krytox 240AC, a nonreactive teflon based grease, and put the base together. I glued the spud into the post mount with some Hysol 1C epoxy. Hopefully that will keep it from turning. I may have to pin it in place.

Everything went together pretty well, one spot I ran into interference between the bottom plate of the main harmonic drive mount and the Az fine adjust bar, it will only get in the way at low altitude settings which will never happen so I am not too worried right now.

Next up, figure out the angle lock and fine adjustment. I have a section of worm gearing that might work nice. I also need to make the dovetail saddle and buy the dovetail kit for my telescope, that will attach the scope to the mount. Then I need to get working on the control.

The taper bearing in place and lock nut:
ImageIMG_8769 by macona, on Flickr

The fine adjuster in place:

ImageIMG_8770 by macona, on Flickr

Side plates on:

ImageIMG_8771 by macona, on Flickr

A view of the base:

ImageIMG_8772 by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Jerry » Fri Jun 13, 2014 12:36 am

On the tripod, this is a standard Meade Field Tripod:

ImageIMG_8775 by macona, on Flickr

Other side:

ImageIMG_8776 by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Starfire » Fri Jun 13, 2014 6:39 pm

getting there 8-)
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Re: DIY Equatorial Mount

Postby Jerry » Mon Jun 16, 2014 12:15 am

I got the declination fine adjuster installed last night. It came out of an old Sperry Gyroscope Tool Set I got a couple years ago. A little overkill but it should work fine. I also made up the clamps for the Dec adjuster as well.

Next is the dovetail saddle for the scope and the mechanical portion of the scope will be done. I need to start ordering some parts for the control system, a couple AM26LS31 line drivers for the step/direction inputs of the servo drives and the bluetooth module for the controller. A guy at the local Dorkbot meeting gave me one of the Orbital LK204 serial LCD/button modules. I might try to use it as a control pendant.

http://www.matrixorbital.com/product_in ... cts_id=207

The adjuster, should barely clear the scope, it came out bulkier than I had hoped:

ImageIMG_8779 by macona, on Flickr

The kit the parts came out of. I had just bought it for the case but figured the rest might come in handy someday.

ImageTool Set, Gimbal Positioner by macona, on Flickr
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Re: DIY Equatorial Mount

Postby Doug Coulter » Mon Jun 16, 2014 9:15 am

Yep, looks like you've created a monster! Now to have a way to rotate the scope around its long axis so long exposures don't smear things that have "features" like planets...which is still a problem with equatorial mounts... ;) Just kidding - no need to add even more till this is working all nicely together and tested.

Where on earth does one get harmonic drives, anyway? I looked that up and they look useful for other stuff. Are they full-propietary and expensive still?
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: DIY Equatorial Mount

Postby Jerry » Wed Jun 18, 2014 9:15 pm

They have never really been proprietary, heck the lunar rover we sent up during the apollo missions used harmonic drives in each of the wheels.

The reason they are so expensive is they are just very precisely made. Each spline/gear/eccentric bearing is a matched set. Ebay is the best place to get them.

Working on getting the controller going now, or I should say others are getting it working. The OnStep controller I want use runs under a Arduino 2560 and I really would like to use a Teensy 3.1. Lots more power to handle the high resolution drives I have. The designer of the teensy and the guy who wrote the OnStep software are working on getting it running on the Arm Cortex on the Teensy.
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Re: DIY Equatorial Mount

Postby Jerry » Sun Jun 22, 2014 11:45 pm

I made the dovetail and saddle for the telescope today. Figuring out where to put the holes to match the existing accessories hole on the scope was kind of a pain, no documentation anywhere on the hole spacing and angle. The dovetail should be compatible with Losmandy type accessories.

I am probably just going to paint these. We will see.

Machining the dovetail on the telescope side.

ImageLosmandy style telescope dovetail and saddle. by macona, on Flickr

The four parts I made today:

ImageLosmandy style telescope dovetail and saddle. by macona, on Flickr

Assembled.

ImageLosmandy style telescope dovetail and saddle. by macona, on Flickr
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