Go-to - (old) Celestron fork

[Chriske]

A long time a go I got two old Celestron8 forks from people who didn't need it anymore. One owner wanted to get rid of the fork because he bought a heavy duty equatorial mount for his scope, and the other I do not remember why he didn't use it anymore(got them both for free btw).
Anyway, my pal Guy and I wanted to reuse these forks and we decided to transform them by installing two steppers + drivers + software ending up with goto-forks.
Guy takes care of  all the electronics and I myself will take care of the mechanical parts and also designing/printing the necessary parts to hold all new components.  
First thing to do was removing both syncro-motors from the fork. (Still can't figure out why Celestron mounted two syncro-motors on that one RA-shaft...? Anyone...?)
As mentioned before both shafts will be equipped with a stepper each, one Nema14 for the Decl, and the RA shaft will receive a Nema11 with built in 1:100 reduction.
Both steppers had to be equipped with a  small gear. That little gear from the old Celestron synchro-motor had to move to the Nema11-stepper. To do this I had to drill a 1/8" hole in the Nema11 stepper's axis. Very odd to see the Nema11 stepper sticking out of the lathe's chuck. Care had to be taken not to damage the stepper in the process. Purpose of this procedure is the see that the little gear will run absolutely concentric with the stepper axis. In the end I managed to 'center out' the stepper in the lathe with only 1/100 of a millimeter shift.
The second gear for the Nema14 was even more 'fun' to do. I completely had to take that Nema14 apart. Care ahd to be taken not to damage the rotor while squeezing it in the lathe's chuck. To protect the rotor in the chuck I made a very thin bronze ring.
A 1:200 reduction was kanabilized from a small DC motor. To join the Nema14 motor and that reduction I had to print a part. A further 1:7 reduction is added on the outside of the fork. That second reduction will be done with timingbelt, a standard 20T pulley + a second 140T (printed) pulley.

That's how far we got. Next step is mount that second (RA) stepper and also print a adapter to hold a smaller scope into the fork. Don't know yet what scope eventually we will be used in these forks but testing the mount will be done with a smaller scope. I have two scope to choose from. One 125mm f/5 cassegrain(in fact a telephotolens) and also a 90mm Maksutov.

I'll post some pictures later on.
I'll also ask Guy to chime in on this thread.  When he does he can give some details about the electronics.
We will be using SkySafaryPro4.
And if I'm not mistaken Guy mentioned using WiFi.

[Gina]

Very interesting   I have a small DIY fork mount on the project list but shelved ATM.  Beware that most of the planetary gearboxes on stepper motors are not exactly the ratio they say.  Could be a problem if you were to rely on exact tracking - no problem with guiding, of course.

[Peter Drew]

It was always considered that Celestron used two motors to drive the RA so that they would run out of phase and reduce backlash in the RA drive spur gear. 

[Chriske]

 

 

[Peter Drew]

There seems to be a rising interest in alternative uses for redundant SCT forks. I "sretched" a 12" fork to take a lightweight 18" F3.5 Newtonian. Next fork mod project is likely to be for a GOTO binoscope using "push to" encoders fron an Orion Intelliscope. Might be the end of "free" cast-offs".  

[Chriske]

Telescope adapter : running...
Even with a 0.7 nozzle : 6 hours (but... if you look closely, you'll find my heatsinks in pictures higher up in this thread. They're for Volcanos up to 1.5(!)mm)
A simulation reveals that this adapter could be printed in 2 hours flat (1.5 nozzle)  (I'll keep you informed Gina..;-)) )

I had to split this thing up reason : to large for my 200x300 bed...;-(

 

 

[Chriske]

Correction, forgot that the telescope should be able to move separate from the timing belt, so new part had to be printed.
Has to do with quick acces to alinment stars....silly me...

 

 

[michael8554]

Ah, brings back memories of trying to add a Dave Ek Push-To to a Meade LX6 - if only I'd had a 3D printer.......

Michael

[Chriske]

We've used that DaveEk push-to system in our Printsonian project(10" f/6 dob). We had it running wireless.

[Chriske]

Scope adapter 

Belt clamp

[Chriske]

There was no possibility to insert an eyepiece, so I had to make an adapter and right angle prism myself.

 

 

[happy-kat]

Did you 3d print that? 

[Chriske]

1 minute ago, happy-kat said:

Did you 3d print that? 

yes, why..?

[happy-kat]

It's very clean smooth looking so wasn't sure. Must make things easier as you can fashion the bits you need. 

[Chriske]

As a matter of fact, all white parts on that fork are all 3D-printed. (I have two printers of own design)

[Chriske]

First test with Guy's 'breadboard configuration' worked remarkably well.
Connection was made via bleuthooth-smartphone-SkySafary4. The 'main' boards are Arduino + RAMPS. Beside these two there was a bunch of wires connected to an extra board of own fabrication.  Can't tell you a thing about it. Electronics is Guy' department. I'm merely the hardware and mechanical man...
Because of the clouds we were forced to do the initial testing inside our workshop. Made a few mistakes during initializing. A few simulations revealed all was working as expected hoped...
Now it's time to find out if all works accuratly enough to 'GoTo'...  These finale tests will have to wait until the clouds move to another country...