10” Equatorial Platform for Dummies

[Time Traveler]

Sounds like a plan, John!  Actually, sounds like it might be a cheap fix, too!  thanks so much  for your time and expertise.

Terry

[DocEE]

I was inspired by this thread and finally got started on a VNS platform (actually several, since the 2 foot by 4 foot plywood sheets I bought were large enough for three!)  I have to confess I have made a simple design more complex in an effort to make this worthy of astrophotography.  My changes: 1) make the vertical bearing segment over the drive roller more "curved" by bending it in two places, since a segment rolling over different places on the roller results in a different distance from the imaginary cone focus and therefore different RA tracking speeds as the platform moves, 2) I added a declination adjustment by using a cheap Chinese 1RPM motor threaded into a long plate under the upper platform board, 3) I have designed and built a simple and cheap ST4 guidance interface.  It allows guidance adjustment via the declination motor and also will speed up or slow down the EQ-1 drive motor for RA tracking adjustments.  That requires soldering two wires to the EQ-1 printed circuit board, but at easily reached places.  The ST4 interface is for use with my ZWO ASI camera.  Each ST4 line basically is connected to an optical coupler via 2 resistors and that drives a tiny CIT J850 series relay (yes, relay!).  That cost me 30 cents for two resistors and one diode, 75 cents per relay from local source and $1 for the optical coupler.  Since I am putting the ST4 interface into a box, I will also add a switch that can go from the 9 volt battery to the same power source that supplies the box, plus will have a $3 voltage display show me the motor voltage. Time will tell if this works for me, as I am still building.  The site seems to have lost the photos I was uploading, so I will try another post.

[DocEE]

Here are some of work from this past week

[PeterStudz]

@DocEE this is interesting, please let us know how you get on.

I have made one of these for my 8” Dob mainly for visual but I have played around with using it for taking short 30 second exposures using an iPhone. As is it works fine for this. It’s also possible to polar align. I’ve tired using the method here (scroll to the end)…

http://www.astrosurf.com/aheijkoop/Equipment/EqPlatfor2.htm

Then marking the position of the platform on the ground. Out of interest here’s a short video of Jupiter with just a rough alignment taken on 21st Jan 2023 with my iPhone 14 Pro. These phone cameras are getting good! And it’s quite steady even at high magnification plus zooming in.

 

I’ve also thought (it’s got no further than that) of using one of these motors in place of the EQ1 motor drive…

https://www.firstlightoptics.com/sky-watcher-starquest/sky-watcher-ra-motor-drive-for-starquest-and-az-eq-avant-mounts.html

I already have one on a small reflector…

As it is it’s single speed but does have the advantage of a clutch and an Auto Guide port. Although whether I can be bothered with the extra complication of this (I like to keep things simple) I’m not sure. I know nothing about Auto Guiding and my electronic knowledge is poor!

Edited February 11 by PeterStudz

[DocEE]

Peter,  The box with the built-in ST-4 control and engagement clutch looks interesting, but I fear it's non-adjustable speed will limit it's appication with an equatorial platform unless you can "hack" it somehow.  A fresh accumulation of 15 inches of snow here in Minnesota will only serve to delay my outdoors testing of things, but before it snowed I did make some progress.  My 2 feet by 4 feet plywood for the top and bottom of my platform was enough for THREE platforms, so that is exactly what I made while I was in the garage, anyway.  I plan to give one to a friend and I'm not sure about the 3rd one yet.  Each one had a bad solder joint or two, but now the electronics all seems to be working.  I changed the value of one resistor and one potentiometer in the end to have more adjustment in my "fine tune" for motor speed.  Any design flaw that exists in one is shared by the others!  Sorry if I am polluting this thread about a simple VNS platform with all my pictures of a setup that is a bit more complicated, but since I got all my inspiration from this thread, it seemed like the place to respond.  I currently have made my VNS segments using the templates provided by Reiner Vogel, but it is possible I will be changing them out for some made using my own calculations.  For those of you with intestinal fortitude, I have attempted to attach a long-winded document (17 pages??) that I put together documenting the time I have perhaps squandered with calculating VNS segments in recent weeks.  It was not written with Microsoft WORD, so the formatting may be awkward when you open it, but perhaps buried in those pages is a useful idea for someone... or not  😉Calculating curves for segments.doc

[noodlehat]

@westmarch @FrankRyanJr many thanks for this guide and both your inputs, its my next project after re doing my dob mount. I just have 2 quick questions: 

- I have a 12" dob with a 700mm diameter circle base with feet at about 600mm diameter , ive worked out i need to scale the plans 15% for its feet to fit on the top board of the EQ mount, I take it I'm just scaling the timber plans and not scaling the aluminium arcs etc? The 50mm gap between boards stays the same and all rods etc?

- Also, if my dob base has a fixed setting circle on it, if I begin with it aligned correctly, will the EQ mounts movement keep the setting circle aligned correctly or will it all go to hell? Is there any way to get a setting circle on the dob base to work with the movement of an EQ platform?

Many thanks.

[westmarch]

14 minutes ago, noodlehat said:

@westmarch @FrankRyanJr many thanks for this guide and both your inputs, its my next project after re doing my dob mount. I just have 2 quick questions: 

- I have a 12" dob with a 700mm diameter circle base with feet at about 600mm diameter , ive worked out i need to scale the plans 15% for its feet to fit on the top board of the EQ mount, I take it I'm just scaling the timber plans and not scaling the aluminium arcs etc? The 50mm gap between boards stays the same and all rods etc?

- Also, if my dob base has a fixed setting circle on it, if I begin with it aligned correctly, will the EQ mounts movement keep the setting circle aligned correctly or will it all go to hell? Is there any way to get a setting circle on the dob base to work with the movement of an EQ platform?

Many thanks.

Hi there,

your plans for the 12” Dob base sound right to me but my advice to Frank stands: this set of instructions works for up to 10” Dobs, beyond that you need to be careful that your centre of gravity, on full tilt, doesn’t end up outside the base.  If it does, you may have to move the tilt limiting bolts inward on the arcs - reducing the travel. 
 

For setting circles, the RA is fine but declination is dependent on your telescope base being level. That means you have to put the platform in the mid. position and you half the possible travel when you switch on the motor.  I have setting circles on mine but find them a bit of a faff and rarely use them; relying on Sky Safari and star hopping instead. 

Good luck with the build. 

John

[noodlehat]

Thanks, yueah i think ive come to same conclusion that the setting circle will be nice to have on the dob base but prob not end up using it it on the EQ platform.

I found the reiner website also has plans for 12"+ version as well 👍

http://www.reinervogel.net/index_e.html?/Plattform/Bauplan_e.html

[westmarch]

It’s been a while since I visited Reiner’s website - it is by far the best resource on the web for self builders. 
 

John

[westmarch]

@noodlehat  Just saw this post by @PeterStudz that may allow you to use an app as a cheap alternative to your setting circle.  Since the iPhone is finding its alt/az independent of the platform, this might work with an Eq platform.

John

[PeterStudz]

2 hours ago, westmarch said:

@noodlehat  Just saw this post by @PeterStudz that may allow you to use an app as a cheap alternative to your setting circle.  Since the iPhone is finding its alt/az independent of the platform, this might work with an Eq platform.

John

Yes, I use it regularly with my EQ platform.
 

In fact I’ve literally just come in after observing the sun in white light. Then, using my phone with the goto feature in the app PS Align Pro, syncing on the sun, I was able to find Venus in daylight. Of course it’ll work at night just as well and you can use your Dob plus EQ platform in the normal way.