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Making an equatorial platform

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#51 sixela

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Posted 07 October 2006 - 04:23 PM

Only when observing south one *could* correct in declination with that motor.


Quite - it only corrects in Dec around the meridian. But even for astrophotography, that's where you tend to image (at least with Dobs - no mirror flop).

If you autoguide one of Tom O.'s dual axis platforms, BTW, given that autoguiding is using a feedback loop, the guiding software can still work even if its two corrective axes aren't perpendicular, though it becomes very hard, of course, close to the Western and Eastern horizon.

#52 Chriske

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Posted 08 October 2006 - 04:21 AM

.... I'm thinking about a redesign if I get serious about photography.
Ed


Keep us informed Ed, once the growing-pains are gone I will copy your design for my 'big on' I'm building this very moment. Although I have the impression the knurled axis will wear out the wood. No problem there...??
I will find me some nice pieces of exotic wood to make it as nice as yours, maybe some 'American pitchpine'... ;)

#53 Mark Harry

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Posted 08 October 2006 - 07:27 AM

My hat's off to you, Ed. Excellent article. I never really understood these things much, but they are very useful with Dobs. I appreciate the insight immensely! Mark

#54 Ed Jones

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Posted 08 October 2006 - 09:35 AM

Keep us informed Ed, once the growing-pains are gone I will copy your design for my 'big on' I'm building this very moment. Although I have the impression the knurled axis will wear out the wood. No problem there...??


From my experience absolutely not and this is the second platform I've made using knurled metal against wood. I do use hard maple for the bearings. I suppose if somehow it got jammed and set there and run for a heck of a long time (at 4 revs per hour!) it might make a divot in the wood but it seems very unlikely. Some use aluminum but it seems just as likely to get nicked or dinged.
I think my wedge angle is too steep. It works but I don't think it will be good for photography.
Platforms are not expensive to make and I think are pretty easy to make too. They work so well that a Dob isn't complete without one IMHO.
Here's a laser holder I made yesterday for polar alignment, I seem to be using this laser on all my scopes.

Ed

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#55 Tele

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Posted 16 October 2006 - 01:20 PM

That is absolutely brilliant!! I am glad I'm not too far along yet. I must use this adjustment idea of yours.
Also I am looking for a suplier of gear heads for stepper motors. I would like to step down a bit more for my set up.

#56 Darenwh

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Posted 16 October 2006 - 08:28 PM

This is the best and easiest to understand article I have seen on building one of these. I feel it deserves to be pegged to the top of the thread. Not only that, but the build quality and looks of this platform are fantastic. I don't want you to get a swelled head or anything :) but you have set a very high bar for future step by step's. I will likely be building one of these for my dob if I ever get it built. I currently have a couple restoration projects (RV6 and home built 12.5" F6 fork mount eq newt) to do but after those, the dob will be built and you have made this look so simple, I will probably skip the ground board and build this directly as a replacement.


:bow: :bow: I am not worthy... :bow: :bow:

#57 Ed Jones

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Posted 16 October 2006 - 08:32 PM

My laser mount?? I set the platform up at ~45 degrees and adjusted the laser to be stationary projected on a wall when I swung the platform through it's travel. The laser has to be set in the same orientation each time because the laser and its barrel axis are misaligned. I have two pins that align the fixture on the platform.
All Electric Corp. has a gearhead 10:1 stepper for $9.50
Ed

#58 Guest_**DONOTDELETE**_*

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Posted 04 November 2006 - 02:37 AM

I just read it over again, it a darn nice Platform and pretty too, but danged if that math doesn't befuddle my MSisized grey cells. All those sine's, cosine's and tangents just whistle over my noggan.

#59 Ed Jones

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Posted 04 November 2006 - 11:25 AM

Thanks Dennis and Daren. Don't worry about the sins, tans and coses Dennis, they are just little buttons on your calculator. :lol:

#60 Mark Harry

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Posted 04 November 2006 - 08:39 PM

I just realised that the motor rollers are facing celestial north, so don't feel too bad,Dennis! Mark

#61 Guest_**DONOTDELETE**_*

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Posted 05 November 2006 - 02:45 AM

Ed,

I was just looking at the picture of the complete platform showing the two motors and something struck me (no it wasn't a big spoon in my wifes hand.):lol: The sector hasn't much room to travel until it runs off one or the other motor. Wouldn't it be better to have the motors a little further in on the sector?

#62 Ed Jones

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Posted 05 November 2006 - 12:32 PM

Dennis,
The rollers or motors should go directly under the teflon pads as close as possible for rigidity as they would be in a ground board. As I recall my platform will track for +/- 30 minutes or an hour of tracking which is I'm guessing pretty standard for most platforms. You could design it to track longer perhaps but then it would end up wider and taller. I think an hour is a good compromise. Watch out for those spoons! :smirk:
Ed

#63 bill martineac

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Posted 25 July 2008 - 06:47 PM

I've completed a 6 inch dobsonian telescope and I would like to build your equatorial platfom. when will you be finished and be able to post the complete project or e-mail a pdf file of it. It will be up to you which would be better.
thank you
Bill
e-mail:
wmartineac172060MI@comcast.net

#64 Ed Jones

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Posted 25 July 2008 - 09:42 PM

Bill here's a recent picture of this platform. I didn't like the performance of the wedge with the second motor, perhaps it was too large an angle. In any case I took that motor off, glued the wedge in place and mounted a DC motor to drive a Newport actuator which pushes a SS post up and down. Works much better and tracks super. I think if I were to do it over the only thing I would change is not to knurl the driveing rods, my most recent platform proved it unnecessary.

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#65 JensDecker

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Posted 26 July 2008 - 11:26 AM

Dear Ed,

it would be great if you could show a detailed picture
of the new solution with the Newport actuator.

Regards,
Jens

#66 Ed Jones

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Posted 27 July 2008 - 09:30 AM

Here's a drawing. I glued a gear on to the shaft of a newport actuator, drilled a 1/2 inch hole to hold a Newport post. I threaded the post deeper for a 1/4-20 bolt for the leg. The travel is only as wide a the gear, about 1/4 inch. I used nylon tipped set screws to adjust the slop out of the post and a set screw to hold the actuator.

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#67 kfrederick

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Posted 27 July 2008 - 09:45 AM

hi ed ever thought about puting a hardware kit together along with directions ?if you do i wont one /cool stuf

#68 JensDecker

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Posted 27 July 2008 - 10:10 AM

Hi Ed,

thanks for the drawing!

Jens

#69 df_2112

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Posted 19 August 2008 - 10:47 PM

Ed, thanks for a great post. I really appreciate your design, very elegant.

I am interested in building a basic platform for my scopes. In the planning I am trying to settle on drive motors. Any thoughts as to whether the 4 RPH motors you are running would drive a platform for a 12.5 and 17.5 inch dob?

It looks as though your would be a less expensive solution than steppers when starting from scratch.


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