Equatorial Platform For Dobs - Kit

[SniffTheGlove]

I am selling almost all of my Lower Power and High Power Rocket Motors next weekend and getting about £200 for the lot.

I would like to start to build a Equatorial Platform For Dobs to help with tracking.

I have look around a bit and can only fine 1 person here in the UK making platforms but they £499 and therefore out of my budget, so would like to make my own.

The wood working etc is it's just making sure all the electronics are the right for the job.

Does anybody know if anyone in the UK sells kits or could list he required parts from say RS Components/CPC/Maplins. It just to make sure I have the correct DC motor and gearing for the 2.97mm tracking speed a minute. I need help as I am not an electronics buff.

[SniffTheGlove]

Not had a reply about the tracking electronics in over a month so it seems SGL don't have any electronic buffs who could help me so I shall try trying myself after xMas using some trial and error.

My simple thoughts are to ignore IT as it could be quite complicated as even though I am a programmer I don't know enough about electronics so I am going to go down the old analog route of a DC motor controller by a potentiometer and with loads of gearings to get the correct rotional speed.

[sixela]

Well, that UK manufacturer seems to use a simple clock drive for an equatorial mount --the cheapest one can find, for the EQ1 mount-- and the gears and bearing to make it work. The drive itself costs around €29 in these parts, so it's certainly not excessive.

[SniffTheGlove]

. The drive itself costs around €29 in these parts, so it's certainly not excessive.

Hi sixela,

Out of interest, do you have a link to this type of drive motor so at least I might get started in the right area with a motor as I have been looking around component suppliers without much luck at finding a slow rpm motor

Thanks

[brantuk]

Sean - try the dob user group (click link in my signature). There's a diy dob eq platform in there somewhere. If I remember right it doesn't have motors, but a motorised dob can be mounted on it. I'm sure it wouldn't be much to run one up, contact the member to see if he has instructions for build and use.

If I find the link I'll post it here

Found it: http://www.equatorial-platforms-uk.co.uk/

Here's a kit one from the states with motors. A lot cheaper but of course there's import duty. Might still be worth looking at for you

http://pw1.netcom.com/~tlsystem/cablet4.htm

[themos]

I would suggest a stepper motor (with appropriate gearing), controlled by an Arduino.

Arduino - MotorKnob

[SniffTheGlove]

I would suggest a stepper motor (with appropriate gearing), controlled by an Arduino.

Arduino - MotorKnob

This is the bit which I am out of my depth with and therefore scares me. The programming side of this is fine it's just the scarry bit of hardware.

I will have to have a look and see what the site does and examples.

[themos]

It's not that scary! You can experiment with steppers found in old printers/scanners.

You can start understanding them with just a battery, some wire and a "breadboard".

[SniffTheGlove]

Sean - try the dob user group (click link in my signature). There's a diy dob eq platform in there somewhere. If I remember right it doesn't have motors, but a motorised dob can be mounted on it. I'm sure it wouldn't be much to run one up, contact the member to see if he has instructions for build and use.

If I find the link I'll post it here

Found it: equatorial-platforms-uk

Here's a kit one from the states with motors. A lot cheaper but of course there's import duty. Might still be worth looking at for you

http://pw1.netcom.com/~tlsystem/cablet4.htm

Thanks, the platform here in the UK is expensive at £499 and I can not justify that to the wife

I have seen the kit from the states and was going to be my "Last Resort" if I can not do it myself. I did not think it would be that hard to do and with recyled parts a lot cheaper than the UK price.

Having got a 10in Dob I would like the simple ability to have some tracking capability so some astro photo can be done without nudging the scope every few seconds. The newer SkyWatchers etc have it built in now for their Dobs and if I get aperture fever then I might just get one of those all built in but that is the future, I have not used my Dob yet but trying to prepare everything ready for the big day soon and get some knowledge and stuff planned or the new year.

[SniffTheGlove]

It's not that scary! You can experiment with steppers found in old printers/scanners.

You can start understanding them with just a battery, some wire and a "breadboard".

I suppose once you start like most things it gets easier.

I have wanted for quite a while to be able to use a PC to contol objects but a few years back it was expensive serial/printer I/O cards and they were expsensive, hence whay it alsways scares me but if Arduino is simple and easy then it might be OK for me to try.

[brantuk]

Fair enough Sean - I'll keep my eye out for a cheaper alternative for you

[themos]

I'm also thinking of adding some tracking capability to my 12" dobsonian. A half-way house would be what I call "meridian tracking". As objects crossing the meridian appear to travel horizontally towards the west, one only needs to track in azimuth. I only need to track for a few minutes around (meridian) "transit" time, anyway (the moon/planets would be as high in the sky as they get). So, I reckon that I don't need a full Equatorial Platform for this, just a gentle drive on the azimuth axis. This should be a lot easier to design, mechanically.

[themos]

Arduinos are cheap. You upload code to them via a simple USB lead. Then, depending on the design, they can control equipment on their own, or they can receive commands from the PC via the same USB lead.

[SniffTheGlove]

Fair enough Sean - I'll keep my eye out for a cheaper alternative for you

Thanks

[Lux1]

How about the old hiss drive, I've made one in an afternoon and it worked very well.

Tom Fangrow's Hiss Drive, from Sky and Telescope Magazine September 1985.

[Moonshane]

I am going to make an EQ platform for my two current dobs and any future ones. It seems to be an excellent way to avoid nudging constantly especially at high mags - it's not a big problem but I think I'll see more detail on planets with tracking.

I'd expect the total cost to be less than £50 each, less than a good ortho.

It will be a single axis drive as I am only looking at visual tracking.

I am also not too hot on the electrics side but think that I can use a battery driven 12v DC 4 RPM motor controlled by a dew heater controller to drive a threaded rod at 2.3 rpm which is what I think I need on one of them per my quick calcs today.

The woodwork seems straight forward to make.

I'll be starting a thread when I start work.

I am just awaiting an answer to my question to a supplier first which is does a faster eg 15 RPM motor 'controlled' to 2.3 rpm create less vibrations or 'stop starts' than a 4 RPM motor controlled 'less aggressively'. If anyone on here can answer that then cheers!

[SniffTheGlove]

I have found a list of parts for the electronics at Google Translate

[Moonshane]

hi Sean

I have loads of sites where there are plans and different ways to do this. I can add them to the thread if you wish or PM them if you prefer.

This seems an awesome idea and although I can handle the 'nudging' the thought of a stable image is very attractive!

[SniffTheGlove]

The plans are easy, just 2 planks plus a segment and easily cut out by yourself or a carpenter. The only dificult bit is the angles of the segment and the bearing.

To me the difficult bit is the electronics and getting a parts list of what someone else had used is important (especially to me) as I do not have to do the research and trial/error testing to get it working with steady tracking. The spreadsheet is under the first picture in that web page or http://www.vangestel.de/fujtor/eq/eq.xls

I tried a simple webcam capture the other night of the moon and it moved quite fast under prime focus so some help at tracking would be great if I can achieve the full build.

[SniffTheGlove]

It will be a single axis drive as I am only looking at visual tracking.

I am also not too hot on the electrics side but think that I can use a battery driven 12v DC 4 RPM motor controlled by a dew heater controller to drive a threaded rod at 2.3 rpm which is what I think I need on one of them per my quick calcs today.

The woodwork seems straight forward to make.

I'll be starting a thread when I start work.

I am just awaiting an answer to my question to a supplier first which is does a faster eg 15 RPM motor 'controlled' to 2.3 rpm create less vibrations or 'stop starts' than a 4 RPM motor controlled 'less aggressively'. If anyone on here can answer that then cheers!

I have found a DC motorgearbox at Maplin that will do 1.5rpm (4.5vdc) to 6rpm (15vdc) so this looks like a suitable motor Moonshane, what do you think? Large Single Ratio Motorgearboxes : Motors Gearboxes : Maplin

The motorgearbox is made by http://www.mfacomodrills.com and they also do variable voltage controllers

Did you get a reply from that supplier to asked the question to?

I am now thinking of redoing the whole dob base, starting with the EQ Platform being the main base with a simple swivel base ontop for the OTA all with the GemRad encoders fitted of the Alt/Az. The EQ Platform would need to be level and then run the tracking on just half of the segment for approx 30min of tracking of 7 degrees. This is ample for webcam capture (which is all I am after) as I can easily reset if needed besides at 360mb per minute of my webcam capture I will end up with 10Gb files which is to large to handle especially over a wifi network.

[Moonshane]

hi Sean

No answer yet but they are probably closed for the Christmas period.

The motor you suggest does look like it would work with the correct controller. I have a dew controller which I was going to use myself.

Doing the maths and based on a rough scale drawing I think I need a 74" diameter circlular section which gives a circumference of 232.5". 15 degrees is 9.68" so it's 9.68" per hour or 0.16" per minute. Using quarter inch 20tpi threaded rod would mean that 20 x .16 = 3.2 turns per minute. If I get a 12v motor and run off 12v battery through the controller I'll be able to just tweak it to the right speed to keep the target in view for an hour (or less). I am also considering a lesser period of tracking for my planetary dob as this is really tall and spindly and I'd be concerned about toppling if I ran to 15 degrees. The COG is in excess of 35" high on a 6" scope!

I'll be starting a thread when I get going in the new year.

[SniffTheGlove]

Doing the maths and based on a rough scale drawing I think I need a 74" diameter circlular section which gives a circumference of 232.5".

First thoughts is that is mighty large diameter (Over 6 foot) to cut the segment from.

[Moonshane]

true but with a centre of mass of 35" and an observing latitude of 53 degrees it's unavoidable I fear. using another version of the excel calculator, I am given approx 29" radius and amazingly a depth of the bearing of only 1.5 inches! (18" wide approx). It will be somewhat different for my 12" dob and ultimately my 18".