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DIY fork or GEM mounts

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#1 friolator

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Posted 18 September 2020 - 09:41 AM

I've got a Meade 2080, fork mounted, LX3 drive - so it tracks but no goto, no slewing. I kind of love it, but because we live in a city, I want to start doing some astrophotography with it, and I have an impatient 6 year old who doesn't like that we can't just see stuff. I'm toying with the idea of deforking the OTA and making my own EQ mount that fits on the existing Meade pier mount I've got. 

 

I'll preface this by saying I have a little electronics experience and am not afraid to solder stuff together. I have a little programming experience, and don't mind a bit of hacking. I've done a bunch of stuff with motors before at work, where we've built custom motion picture film scanners for in-house use. I have a decent 19" x 19" CNC router at work that can easily cut 3/4" aluminum, I've got a small 7x14 metal lathe, and a small drill press. 

 

What i'd love to find is a set of plans that i can use to build my own setup. Has anyone ever put something like this together, with CAD models available? I'd obviously have to design my own interface to the pier, but that's not a big deal. 

Thanks!


Edited by friolator, 18 September 2020 - 09:47 AM.


#2 sc285

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Posted 18 September 2020 - 11:02 AM

Noble idea, but I wonder if in the end, it would not be cheaper to just buy a commercially made mount.

You have to consider what all goes into that mount. You say you have a little electronics experience, but enough to put together the boards needed to control and drive the mount; You say you a little programming experience but is that enough to program the controller and drivers for the electronics + program in the necessary parameters and catalogs to make it work? Would would still have to invest in a set of gears/worms which would not be cheap. 

I suppose you could find plans to build an EQ mount, and find plans for electronics/software for such mounts, but I doubt that it would be suitable for nothing more than a visual scope with tracking/goto. I doubt it would incorporate the finesse needed for any serious astrophotography. 

Back in the day (30 yrs ago), I built a large EQ mount to hold a 14" short focus Newtonian. It had 3" shafting and weighed **** near 200 lbs when assembled. It was going on a permanent pier. Put a slow motion tangent arm on it for the DEC, and used a Meade drive motor off their DS-16 for the RA. That was back when astrophotography meant sitting at a guiding eyepiece and keeping a guide star in a small circle on the reticle - for hours. 

With todays mounts and the software that can be used with them, the days of "rolling your own" are just about gone. It's just cheaper to buy commercially and know that it's gonna work out of the box (and if it don't there is a warranty). 

Just my 2 cents worth....you mileage may vary.

 

Rob



#3 tommm

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Posted 18 September 2020 - 11:47 AM

Tom Stock had a thread here several months (?) ago on making his own equatorial mount with pillow block bearings. I think one issue you will have is sourcing worm gears to fit your axes. He hobbed his own.

Edit: Ah, here it is.

 

As far as electronics, I suggest OnStep. It will save you a lot of time designing your own and has a lot of refinements and features a home brewed one likely won't have.  It normally operates tracking position by counting steps. There is some provision for adding encoders but would take some work I think. You would have to inquire with Howard, the creator of OnStep.


Edited by tommm, 18 September 2020 - 11:52 AM.

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#4 friolator

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Posted 18 September 2020 - 02:55 PM

Hmm. thanks for the feedback. I was thinking something that uses stepper motors and pillow block bearings as well. That looks like a nice mount that Tom Stock made, and I'd certainly consider something similar. I have no issues with putting together Arduino or Pi based setups, so using OnStep was more or less what i was thinking. 

 

that being said, I also have a million other unfinished projects, and the more I think about it, the more I wonder if I'd ever even finish it. The savings might not be worth all the time it'll take to machine though. Were there readily available CAD files, I'd give it a whirl, since a lot of it would be CNC cutting time. I'd probably have to buy the gearing because I doubt my crappy lathe is up to the task. Good for turning simple stuff, but not exactly dialed in enough to do worm gears.

 

I'll probably take this over to the mounts forum and see what my options are. 

 

Thanks




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