10” Equatorial Platform for Dummies

[Buford7]

@PeterStudzYes makes sense!  I have been reading up since I posted and that was what I was imagining it needed to look like. Very helpful—Thank you for confirming.  Now to just wait for the parts to arrive. 
 

Cheers!

Graeme 

[Buford7]

Well—here are some pics of the finished product from this month’s build!  I’m very happy with how it’s turned out.

 

Many thanks to the great information, instructions and modification ideas on this thread.  
 

I’ve added a removable jig for a green laser pointer that can stay in place temporarily via magnets so I can more accurately polar align the platform to Polaris through the polar axis of the mount (54° angle for my latitude).  

Everything seems to be working in theory. Now waiting to get some clear skies to try it all out for real!  😊

Edited May 31 by Buford7

[Mr Spock]

That looks really nice 👍

[Buford7]

12 minutes ago, Mr Spock said:

That looks really nice 👍

Thank you! 

[westmarch]

Lovely build. I hope you get a chance to use it soon. Let us know how you get on.

John 

[PeterStudz]

That looks top-notch! And do let us know how it all works in practice. 

[Jim Smith]

I've started! Thanks to all contributors to this thread.

[westmarch]

looks like you have already done the hard stuff by sourcing the kit. Good Luck!

John

[PeterStudz]

2 hours ago, Jim Smith said:

I've started! Thanks to all contributors to this thread.

I’ve found mine so useful that if it broke I’d have to make another one. Looks like you are doing similar to the way I went about making mine - sort of make a kit of parts and then assemble it towards the end. Once you get to that stage I found it quick to out together. 

[GasGiant]

There are some really great builds here. Seems like it's inspired a lot of people 😃

[Jim Smith]

Well, it seems to work. I just need a clear sky to try it out. I'm hoping to shoot those planets in a few months time.

 

 

[westmarch]

Looks like a very professional build. I hope it gives you a great and stable experience. Tonight looks promising here!

John

[Tim Harbour]

Hi all. New to this forum.

I live in Australia so Southern Hemisphere.

https://en.m.wikipedia.org/wiki/Wauchope,_New_South_Wales

I'm needing some templates for 58.5 degrees for where I live to make an EQ mount for a 10" Dob I'm looking at purchasing.

I've searched and searched for an easy calc to do it for me but seems beyond my understanding.

The closest I've found is 56 degrees. 

Would someone be able to help me with a file I can print out at 58?

Or will 56 be close enough for general viewing?

Also do we place the base facing true North or to a particular star?

Thanks in advance. I've loved looking at everyone's creations on this thread, very inspiring.

Tim.

Edited September 23 by Tim Harbour

[Ratlet]

24 minutes ago, Tim Harbour said:

Hi all. New to this forum.

I live in Australia so Southern Hemisphere.

https://en.m.wikipedia.org/wiki/Wauchope,_New_South_Wales

I'm needing some templates for 58.5 degrees for where I live to make an EQ mount for a 10" Dob I'm looking at purchasing.

I've searched and searched for an easy calc to do it for me but seems beyond my understanding.

The closest I've found is 56 degrees. 

Would someone be able to help me with a file I can print out at 58?

Or will 56 be close enough for general viewing?

Also do we place the base facing true North or to a particular star?

Thanks in advance. I've loved looking at everyone's creations on this thread, very inspiring.

Tim.

You should face it south in the southern hemisphere.  I think 56 will probably be close enough as they are usually sold in 5° ranges.

[Tim Harbour]

Thanks for your help .

I will give 56 a go.

I did read somewhere too you can tilt the platform a degree or 2 also to off set it if needed.

 

[westmarch]

I think the advice from @Ratletis good. You should be close enough. Don’t forget the EQ1 drive has a southern hemisphere switch to reverse its direction. Let us know how you get on. 
John

[PeterStudz]

And just to be clear… the platform only needs to be aligned north-south by compass. You don’t need to align to a star as this is more than good enough for visual. So it’s a quick setup.

[Nathann]

Hi all,

First post on here. I’ve been looking at building an equatorial platform using Reiner Vogel’s VNS templates and was wondering if anyone knew the diameter of the North bearing circle he used before being squashed and rotated? This would be a great help to verify my design.

thanks,

Nathan

 

[westmarch]

Hi Nathan,

you may be on the wrong thread here. We mostly try to simplify the construction because the maths are a bit impenetrable. 

John

[Ratlet]

I'm pretty sure that the diameter of the circle is a function of the center of gravity of the dob as well as the angle for you latitude.  No idea what was used in the default though.

I designed mine in Fusion360 as you can avoid almost all the maths there and just do it by rotating the view and projecting the previous step onto it.

[rbc1225]

Brand new here. Can someone point me to a link for the kit as shown above? I tried searching but no luck. 

[Ratlet]

24 minutes ago, rbc1225 said:

Brand new here. Can someone point me to a link for the kit as shown above? I tried searching but no luck. 

A commercial solution would be this:

https://www.firstlightoptics.com/equatorial-astronomy-mounts/omegon-dobsonian-polar-wedge-tracking-platform.html

Just make sure you get the correct one for your latitude.  If you are not in the range covered you'll need to build your own (and probably get creative with regard to the pivot)

Edited October 6 by Ratlet

[G_N]

Evening all - this is my first post, but further to Nathan's question earlier on this page (we are trying to design a platform for my 10" Starfinder and home made Dobsonian mount):

We have followed Vogel's explantions, and have got some way into designing the platform, however, there are a few things that aren't clear:

1) Once you've got the Circular Segment positioned correctly (perpendicular to the north axis), it's easy enough to project the section when looking "straight-on" to the platform (ie it forms an ellipse) , but for the rotation to angle the segments relative to the centreline, where are the axes you rotate the each segment about?  It's a vertical line somewhere offset each side of the platform centreline, but where isn't specified. Presumably if it's wrong, the rotation of the platform won't be correct?

2) I don't understand how the templated segments work: I understood that the whole Equatorial platform design was based "heavily" (ha ha) around rotating the telescope and base around it's combined centre of mass. But I can't see where this is accounted for in the plans that use the templates? Surely if this is wrong, then the platform could fail to work due to the motor not being powerful enough to turn a potentially grossly out of balance assembly?

This is why we'd like to know the diameter of Vogel's initial Circular Segment - so we can ensure it's positioned such that our centre of mass is on the rotation axis, and then we can confirm that our geometry is right because or CAD for the segments should still match Vogel's templates. We are at 53 degrees North btw.

We are using Fusion 360 for the design.

Any comments much appreciated! Thanks.

[Ratlet]

Great minds think alike @G_N!  You're making your base the exact same way as me.  I'll try to get a look at my plans tonight as I can't remember exactly how I designed mine.

With regards to the templated segments they will work well enough because for the Dobs that they are designed to fit they are all more or less using the same design.  For a generic design you can also largely ignore the centre of mass of the solid tube the itself as it will more or less be in the middle of the base.  You are correct though that if the design ends up out of balance you'll find the motor won't turn it.  If you have a look at some threads on the forums youll see cases where people have had to use additional/different motors or teeth, rubber strips etc to get additional torque.

 

[PeterStudz]

I constructed the “generic” design on this thread, closely following the instructions. Most of the deviations were personal and/or cosmetic. I have an 8 inch Dob and as is it worked perfectly first time, without messing about or doing any maths. This sort of Maths isn’t my strong point, but it’s obviously some do enjoy it! My impression is that it’ll work just fine for 8” to 10” without any need to adjust anything. I’ve even done some astrophotography using mine. 

However, I did find a good balance point by practical methods. I just moved the base around on the top platform, a bit at a time, watched the motor (I was also observing at the time too), until I had a position where the motion was nice and smooth. Then drilled slight recesses for the base feet so it would slot into correct position every time. I never had to resort to another motor, rubber strips or teeth. 

However, if you are being picky centre of mass is important. Eg I have an eyepiece tray that is relatively high on my Dob base. Loading this up with eyepieces does change the centre of balance and I found that I had to adjust the motor speed to compensate. At first I didn’t know what was going on, but worked it out eventually. Similar happened when I took my balance weight off the back end of my OTA and placed it on one side of the base. It only weighed 600g but certainly made a difference. Heavy 2” eyepieces can make a difference, although balancing the Dob with a counterweight to compensate and it should be fine. But this is being picky. For visual (which is the objective in this design) it’s more than adequate. The big appeal for me was how simple this EQ platform is. The only power tool that I used was an electric drill. All construction was done outside on a garden table. There’s no need for computers, 3D printing, complicated geared motors, or any great DIY skills. 

 

Edited October 8 by PeterStudz