RA drive for unidentified mount

greg46 (Greg) · #1 27-02-2016, 11:35 AM

Hi All
Am restoring my old 6" f9 I made in the mirror grinding days 40 years ago when 14 and starry eyed (still infected). Came across old mount (see attached) and would like to add an RA drive. To have a clock drive was a dream in the old days. The worm gear needs to turn at 0.1 rpm but stumped how to proceed. Would prefer adapting an off the shelf drive but there does not appear to be anywhere to fix the motor. This is old time stuff but want to stick to DIY for the fun of it and learn. Would greatly appreciate any advice as have no experience of this. Perhaps someone can identify the mount which has no markings I can see. It may be a Taiwan clone used by Tasco but don't know.
Cheers

bojan · #2 27-02-2016, 11:45 AM

It is EQ-3.. Motor driver is here:
http://www.ozscopes.com.au/skywatche...eq3-mount.html
But you still need gears.

Maybe I can help with DIY.. I did this mount quite some time ago.
Still have PC boards for clock drive (it is different from what is shown on the linked pics, it actually fits inside the mount.
It doesn't matter what kind of gears or belt pulleys you have, as the software can be easily modified to fit almost any mechanical reduction.
http://www.iceinspace.com.au/forum/s...nt+wide+fields

This mount is very good for wide fields, not too heavy for carrying around, capacity is up to 1.5kg, not more.... just enough for 200-300mm telephoto lens (like Canon FD 300mm F4).

torana68 (Roger) · #3 27-02-2016, 12:10 PM

Chinese , as supplied with some FOCO brand stuff.
something like this may work:
http://www.ebay.com.au/itm/SkyWatche...96QBrmUEVvL5AQ

you'll find the gears on the slow motions do not fit well and are a bugger to get right

or maybe this one, quite a few to search through....
http://www.ebay.com.au/itm/RA-Telesc...Q0S2dZGlJpaAFg

MattT · #4 27-02-2016, 12:18 PM

First count the the teeth on the RA gear. Just count how many full turns of the knob it takes to get the RA to move 180º. An EQ3 has 130 teeth (for a full 360º turn) so 65 full turns and you'll know. An EQ5 has 144 teeth. Looks like an EQ3. A perfect place to mount a motor is from a bracket you make to fit where the bolts holding the worm assembly are...looks like enough room.
Lotsa fun.

Matt

greg46 (Greg) · #5 27-02-2016, 03:35 PM

Thank you all for the great info. Very much appreciated.
It looks just like the EQ3 you scored Bojan despite the off white colour. Very snazzy job and clarified how a drive can be mounted. I will have to do some boning up now.
On the matter of the number of gear teeth it takes 6 full turns of the worm shaft to do 1/12 of the 180 degrees. I ran it for 60 degrees and that was right on 24 turns so that has got to be 72 for the 180 degrees and led me to think the final gearing should deliver 0.1rpm. Does that sound right for a normal EQ3 in case this is a clone? Is the final gearing rpm usually specified with commercial motor drives?

bojan · #6 27-02-2016, 03:42 PM

Quote:

Originally Posted by greg46

Thank you all for the great info. Very much appreciated.
It looks just like the EQ3 you scored Bojan despite the off white colour. Very snazzy job and clarified how a drive can be mounted. I will have to do some boning up now.
On the matter of the number of gear teeth it takes 6 full turns of the worm shaft to do 1/12 of the 180 degrees. I ran it for 60 degrees and that was right on 24 turns so that has got to be 72 for the 180 degrees and led me to think the final gearing should deliver 0.1rpm. Does that sound right for a normal EQ3 in case this is a clone? Is the final gearing rpm usually specified with commercial motor drives?

My EQ3 has 144 teeth on the worm wheel, so its the same as yours
In general, final rpm could be anything (for example, EQ6 has 180 teeth on worm wheel).

You can find the motor with driver here:
http://www.ebay.com.au/itm/5V-4Phase...IAAOSw4SlV8kDo

Gears and/or timing belts and pulleys you can find here: https://www.smallparts.com.au/
Or inside old printers, scanners..

You only need to add stepper sequencer.
There are number of designs available, some of them are for Arduino board (Google OnStep, AsroEQ, Ultrascope).
Or, you can go with my solution.

MattT · #7 27-02-2016, 03:50 PM

I got those numbers off the internet....so you can't believe everything you read...and I have an EQ3 as well...

brian nordstrom (As avatar) · #8 27-02-2016, 04:01 PM

This is an origonal Mizar mount , these have been cloned in recient times but the clones are a poor copy of the origonal Mizar mounts which are very good , as good or sturdier than the EQ3 Chineese ,, again clones of Vixen's excellent Super polaris mounts , whew

.

Here is my wifes Mizar from the early 70;s and I have looked into mounting an EQ3 drive to it and as Matt and Bogan say its not hard to retreo=fit a new drive to these , and on that these have 144 teeth like the EQ3 so they will track quite well .

Here is our Mizar and 80mm f12.5 OTA , its a nice scope .

Brian.

bojan · #9 27-02-2016, 04:45 PM

Quote:

Originally Posted by brian nordstrom

..... and as Matt and Bogan say .....

I am Bojan, and I am not bogan

brian nordstrom (As avatar) · #10 27-02-2016, 04:46 PM

OOPS .,
Brian.

Quote:

Originally Posted by bojan

I am Bojan, and I am not bogan

janoskiss (Steve H) · #11 27-02-2016, 05:03 PM

Best price I've seen from local dealer is at Astro Pete's: http://astropetes.com.au/accessories.html
I'd steer clear of Seben (ebay link in post above). They sell some of the cheapest junkiest gear on the planet.

doppler (Rick) · #12 27-02-2016, 10:20 PM

I fitted this ra drive motor to the slow motion control. I had to drill out the hole in the coupling a bit to fit the shaft. (I have since found out that you can buy different sized flexable couplings on ebay) It runs of a 9v battery which lasts for weeks. It was celestron branded from aust geo shop for $50 but I think that they have been discontinued but are still available on ebay.

greg46 (Greg) · #13 29-02-2016, 05:22 PM

Thanks again to all for the great posts.
Still looking at an off the shelf solution for the moment although Bojan has the elegant solution.
Have discovered the commonly advertised EQ3 drives are for the EQ3-2 mount which has 130 worm gear teeth (as MattT mentioned) vs 144 for the older EQ3. Nonetheless they look an easy fit. The EQ5 drives may be for 144 teeth but gears look tricky to fit.
Does anyone know of any off the shelf drives that would drive the EQ3 gear without difficult modification? 144 teeth drives were common as I believe.
Cheers

MattT · #14 29-02-2016, 06:51 PM

Hi Greg,
A place to start should be count the teeth on the RA. This will mean removing the worm. I would, and have done, put a dot of white out on a tooth and using a pencil turn the gear and count the clicks of the pencil until you get to the white dot. This might take a few goes to get it right....I know from experience.
When you have a number you'll know what drive and steppers to buy. EQ3 or EQ5.

I'll try and count my teeth on my EQ3 in the next few days if that is any help. I have no idea really just bought the EQ 3 drive that worked.

Matt

greg46 (Greg) · #15 29-02-2016, 10:55 PM

Hi Matt, no doubt that it is a 144 teeth gear at 72 turns per 180 degrees same as Bojan's but the EQ3 drives advertised are for the EQ3-2 with 130 teeth and 65 turns per 180 degrees. Bit of a quandary but can probably manage with that for my visual usage by just stopping the motor occasionally to correct the higher speed.
Guess I can upgrade if I want more out of the mount unless someone knows of the ideal off the shelf drive for the older EQ3.

MattT · #16 06-03-2016, 07:56 AM

Hi Greg,

If you haven't seen it look at this thread from CN in the Classics section.

http://www.cloudynights.com/topic/52...t-to-make-one/

Lots of info. Seems the small 9v RA drive that Rick has a wide range of adjustment.

Tried to count my EQ3 gear but can't find the correct sized hex spanner to undo the grub screw holding the collar to the shaft. One of the disadvantages of the EQ3 drives.

Matt