Current Project

[astro_nutt]

I've been working on a new EQ mount based on the old Horseshoe design. So far it has gone together better than I thought, although I still have the optics to complete.
Eventually it will be used to do short duration Astrophotography.
It started when I was given an old 10"dob tube a few years back. I have a 10' dob in my backyard but it doesn't get as much use as I'd like.
I drew the plans to make a new mount and using the mirrors, etc, build a new scope while keeping the original intact.
The mount is built from plywood of various thicknesses. The motor drive is from Jaycar with a few extra bits from an old photocopier plus a harmonic wheel for the final drive.
A truss-tube will be built for the optics then some fine tuning with copious amount of Earl Grey tea.

[Rod]

This looks fantastic! Beautifully built.

[Kunama]

Great work on the mount ! Keep the updates coming

[Rac (Raymond)]

Neat. I like the colour!

[mswhin63 (Malcolm)]

I want to make one of these to replace my DOB mount. This look really good. Has been really hard to locate plans with confidence for the last few months.

[Mokusatsu (Australia)]

I love ring mounts, I will be probably trying to build one next year when I get the budget.

I can handle the woodworking and design part of it. With a router and a few bits and pieces perfect circles are easy to make from plywood and the rest is just a matter of accurate cutting on a table saw or something.

But the motorisation is where I am relatively clueless, especially if I want to go even further and equip it with goto abilities and object tracking, controlled by an astronomy app on my iPad or something.

Assuming I can manage the mechanical part of attaching it, how "off the shelf" are motors and all of that other stuff these days?

Travis

[pixelsaurus (Mike)]

Oooooh. I've looking at one of these for my 12" Newt. Choice. Well done.

[astro_nutt]

I worked out the motor drive from a previous project.
I've built an Astrolabe with a RA section which shows the 24 hours in 1 mm increments.
So 24 hours x 60 minutes = 1440 minutes and 1 minute = 1 mm This gave me a wheel with a circumference of 1440mm. Divide 1440 x Pi (3.1415) = 458.379mm diameter for the Astrolabe.
I used this formula for the diameter of the ring portion of the mount to suit the scope. The mirror box section required a ring with a diameter of 696mm. So 696mm x Pi = 2186.484mm is the circumference of the ring. To convert this into mm per minute, divide 2186.484 into 1440 = 1.518 mm would equal 1 minute of the rings circumference.
The motor/gearbox unit I purchased for my local Jaycar which has a final drive speed of 2.93 rpm at 3 volts.
I built a further reduction drive gear and a drive shaft. This in turns drives a harmonic wheel attached to the drive shaft which turns the ring.
So now the Motor drive shaft rotates at 19.30mm per minute.
The Drive shaft for the Harmonic wheel is 9.85mm x Pi = 30.943mm in circumference.
The formulation for the circumference of the Harmonic wheel is as follows,
19.30mm per minute divided by 1.518 = 12.739.
12.739 x 30.943mm = 394.18mm for the circumference of the harmonic wheel.
I hope this helps!

[OzEclipse (Joe Cali)]

Originally Posted by Mokusatsu

I love ring mounts, I will be probably trying to build one next year when I get the budget.

I can handle the woodworking and design part of it. With a router and a few bits and pieces perfect circles are easy to make from plywood and the rest is just a matter of accurate cutting on a table saw or something.

But the motorisation is where I am relatively clueless, especially if I want to go even further and equip it with goto abilities and object tracking, controlled by an astronomy app on my iPad or something.

Assuming I can manage the mechanical part of attaching it, how "off the shelf" are motors and all of that other stuff these days?

Travis

There are numerous off the shelf systems available.

This is just one popular type used for dob and eq mouts

http://www.stellarcat.com/

These people sell gears and servo systems but may require more work from you to put them together
http://www.gototelescopes.com/servocontroller.htm

Basically, there is a wide spectrum from off the shelf to DIY.

[mswhin63 (Malcolm)]

I have a 1 RPM motor and a simple 25A motor speed controller from a EQ Platform previous project. This means for the interim I can get the dimension and make some something quickly with the wood and get it functional before stepper motor controlling later.

Wonderful project and so simple re calculations.

[astro_nutt]

Thanks for the kind words guys!

[Somnium (Aidan)]

looking great, can't wait to see the final result

[astro_nutt]

Starting work on the optical sections from the components in the last photo.
I drew up a full sized plan using A3 paper taped together and used this to calculate the length of the trusses, mirror box, various clamps and mounting points.
The benefit of this is to ensure that the optical design is keeping with the mirrors' F/L.
I decided on an open truss with an adjustable top section which can be moved towards the primary mirror 50mm to allow the focuser to accommodate for cameras, etc.
This design will allow me to rotate the top section in 90 degree steps to position the focuser wherever it suits.
More to follow!

[LewisM]

Wonderful attention to detail, aesthetics and craftsmanship!

I love it when someone takes the time to make something as humble as plywood look like furniture. I absolutely cringe when I see someone use a piece of ply, leave the maker's ink stamp etc on it (and sometimes the sales sticker!) and then slather it in polyurethane.

Kudos sir for a FINE, precision mount.

[AlexN]

I might have to pick your brains on this one day mate. I'm working on a tracking setup for a 12.5" dall kirkham ota for planetary imaging. This is exactly what I want to do. Fantastic work

[astro_nutt]

Thank you LewisM. I also agree it only takes a bit more effort to get better results, as I have seen from others in this forum. I love working with plywood as you can make it to any thickness you desire. I chose to stain all the ply pieces in deep Mahogany and finish off with 4 coats of satin varnish from a spray can.

Thanks again AlexN. I'll be documenting this project soon and submit it to the project and articles section.
I'm also looking to make improvements once I iron the bugs out, and that only take a bit more time to sort out!

[AlexN]

Looking forward to it. I hope to build myself something that will be able yo carry this DK because a gem for it would cost a mint.

My initial plans were to make a base/stand for it also to make the eyepiece at a suitable level for seated viewing. I'm designing the scope to operate at nasmyth focus so the focuser should be at a reasonable location in most positions.

[astro_nutt]

Started work on the top section using mostly aluminium for the strut anchor points. The struts themselves being 16mm tubing will have solid aluminium billet placed inside where the they attach to the anchor points. The plywood mirror box and tube rings are now ready for finishing. I still debating on either flocking the interior of the tube sections, make a set of baffle rings, or matt paint. Lots more work to do and more tea to enjoy!
Cheers!

[astro_nutt]

I've just finished the pieces for mounting the secondary section on top of the truss ring. The clamps will allow the secondary section to move to or from the primary mirror.





The next step is to paint the remaining pieces then to align and assemble everything, which is always great fun!
More to follow!

[astro_nutt]

Hi all! It's been a while but now I'm at the stage where the optical section is near completion.
Just briefly, I have finished the tube sections in gloss black. The plywood rings in Mahogany, and the struts in polished aluminium, which I will allow to slowly oxidize over time. All the strut mounts are made from aluminium.
I just need to fit a friction brake for the declination axis.
More pictures to follow.
Cheers!