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10” Equatorial Platform for Dummies


westmarch
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So I finally found the time to build my equatorial platform following the excellent plans and advice here :)

Using the garden table as a workbench like a pro 😆

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For the pivot I found this ball bearing on amazon, so I gave it a shot. Works quite nicely and it might be possible to adjust the latitude angle of the platform a tiny bit by adjusting the upper screw.

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I REALLY like the playmobil idea of rojay to check the angle of the whole setup, however I couldn't manage to get as nice a photo as he did. So I did it the other way round, put the camera on the platform, aimed it at a ruler and did a long exposure while tilting the platform.

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Which produced this funny image:

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Using the value at the rotation center and the distance of the pivot to the ruler and from the ground and doing some arctan online math, I get this:

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Which by mere coincidence is EXACTLY the latitude I am at :)

Added some adjustable feet and a spirit level, got a new compass and here we go, working quite nicely.

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This improved the Dobson experience soooo much for me, so thanks everybody here again, I couldn't have done it without these resources here.
Now, I do have one more gimmick for my setup, that makes Star Gazing for me absolutely perfect, especially in addition to the EQ platform: the Celestron StarSense Explorer. It's a bit offtopic but I will quickly mention it, just in case you never heard of it, because it really complements the EQ platform perfectly and I am absolutely loving it.

It's basically a Push-To expansion that is using a special mirror bracket for a smartphone and an app that does plate solving of the stars the cam sees. The weird thing is you have to buy a Celestron telescope (!) that comes with it, cause it is not available separately. With some leftover aluminium I built a custom attachament for the shoe where the finder of the dobson used to be.

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You have to adjust it once, so that the Phone Camera points in the same direction as the telescope and then you just choose the Space Object from a library, follow the directions on the Phone and *BAM*, it's right in your telescopes view - and thanks to the EQ platform, it stays there :)

I still can't believe how much easier and better it is now to look at the night sky... thanks again to everyone!

Michael

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Good work on the platform and the StarSense mod. I'd love to do the same but I am to DIY what Johnny Vegas is to hang-gliding!

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Hi Michael, 

Excellent build and ingenious use of the Starsense add on. I must confess to being a star hopper myself but I have a mate who has one and swears by it. 

Hope you have many clear nights to enjoy it. 

John

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3 hours ago, westmarch said:

I must confess to being a star hopper myself

Yeah, that’s much better. With a navigational device you always risk never learning your way around. There are so few occasions I can use my telescope though, mostly under light polluted skies, so I try to make the most of it. 

Clear skies to you as well :)

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Posted (edited)

Here are my build components. Nice neighbour cut the board for me. The motor might need a different bracket to get the drive in the right place and I need a joiner between the 8mm rod and smaller eq1 shaft but I am getting there.

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Edited by mdstuart
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  • 2 weeks later...

File the segments you say....easy to work with? So sandpaper? Keep going until the segment just uncovers the curved line? Deploy the dremel? We shall see.

Cutting the steel rods blunted my hacksaw blade.

Now I know why I stick to spreadsheets. 

No seriously it is fun to try practical stuff.

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Mark,

Spreadsheets have their place but you will struggle with sandpaper - really only for wood.  You will find a flat file a lot easier. You will need it anyway, to to round off the tip of the bolt pivot that is going into that depression.

John

 

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This what I call quality plywood.! hard to find these days here.🇧🇪
Most of our plywood comes from ROC, and-it-is RUBBISCH...!!!

Nice platform btw..!..:thumbsup:

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Ideally, the edge should feel smooth to the touch and be at right angle to the surface. Aluminium should be able to be filed smooth in about 5-10mins with the average flat file. 
 

John

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So, I`ve been making a prototype platform for my 14" dob and was following the type of design with an angled north bearing (not sure of the exact name of that type) . Done all the maths for centre of mass which made the base a bit longer between the north and south bearings than I might have wanted. I carried on and settled on it being friction drive with a wheel driven by an EQ1 motor pressed to the curve of the north bearing. Still got to test it out yet, however now seeing the this thread which shows the simplicity of the design for a VNS platform I`m convinced I am making it harder for myself than I need to so I think I will change tactics and work on producing the VNS type. I`ve attached pics of what I have produced so far. @mdstuartIf you can get hold of an angle grinder with a fine sanding disc that could make it quicker to get the curve smooth, you would just need to go easy so as not to dig in and take too much off. Using a drop of oil or tallow will help a lot when working aluminium because it stops files and discs clogging up. 

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Hi Phil,

can’t comment on the Poncet design you opted for but it looks like a solid build.  A 14” is a heavy scope so your EQ1 motor might struggle but it looks as if you are nearly there with the work.  I think it would be a shame to not try it out before changing the design.

The one piece of advice I would offer is to edge your chipboard with iron on tape. Once the board starts warping with dew entry into the exposed edges it quickly becomes useless .

John

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I did keep the weight of the scope in mind so I focussed my calculations around the centre of gravity in the hope that it would help the motor cope.  I will definitely try it out anyway.  Now I am wondering if the motor will cope better with the Poncet design or the DNS design.  The appearance of the  DNS design looks like it can cope with the weight of a heavy scope better and could help maintain good contact with the driving surfaces.  At the moment I am having to use a spring to keep the wheel in contact with the driving surface which I feel might not be ideal.   The platform I have produced so far is a kind of a rough build try out, so the plan will be to have the north bearing curve made of aluminium plate instead of plain wood so then there is no worry of warping wood and dampness.  I do have plans to make the final design I settle on entirely out of metal. 

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I did a quick test run with the 10" dob and found that the platform did counter the Earths rotation but only slowed down the drift of a star by about 50%, that was with the motor on full speed. So I am wondering if the current idea of friction driving with a 40 diameter wheel does not match well with the speed that the EQ1 motor can achieve. However going by the DNS design, driving an 8mm rod which is in contact with the North curve appears to work correctly. If that is the case it could be a tick in the box for the DNS design. 

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  • 4 weeks later...

New guy here, I am looking to build one of these for my 8" dob, I pretty much have everything I will need here, but have a couple questions.

Could you extend the segments (following the same curve) to get longer times between resets, or would that put the platform/telescope on too much of an angle?

And would changing the angles on the top plate to bring it to the tip of the segment, change how it would work? (so you don't have that point sticking out)

Dave

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On 24/06/2022 at 02:17, DWV said:

New guy here, I am looking to build one of these for my 8" dob, I pretty much have everything I will need here, but have a couple questions.

Could you extend the segments (following the same curve) to get longer times between resets, or would that put the platform/telescope on too much of an angle?

And would changing the angles on the top plate to bring it to the tip of the segment, change how it would work? (so you don't have that point sticking out)

Dave

Hi Dave,

extending the segments would mean that your centre of gravity could end up outside your footprint at the end of the travel and the scope would topple over. 

You can make the top board bigger if you wish. I think most designs try to make the rig as small as possible to reduce weight and improve portability. 

Good luck with the build.

John

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