Localy Built Dob EQ Platform/Table

[netwolf]

If we can get sufficent intrest in this perhaps someone would be willing to bulk produce them for us at a resonable price for there effort.

1. Is there anyone out there with the capability or contacts to produce these?

2. Would all you dob owners be intested in buying these?

3.Requirements:
1. Dual Axis to track in RA and make adjustments in DEC if required.
2. Method to allow simple polar alignment.
3. Handle 6" - 12" Dob's. Perhaps even 16".
4. Adjustable Latidude.
5. Option for Intelegent DSC's (Argo Navis) to provide Slew control.
Any other requirements people can think of?


Thanks and Regards

[slice of heaven]

You'll find a lot of 'interested' dob owners , but the total price of the platform and DSCs is a constraint for most.
I've always thought it'd be a nice addition to mine but the cost and extra setup time for viewing has been the things stopping me.
But now I've 2 dobs at my disposal,one I could leave standard, and if the price was right, maybe....

[netwolf]

The EQ platform would work independently of the DSC, so you need not have this. The EQ Platform controller (brain) however could have an option to hand over controll to a DSC if you have one. Note this hand over is for Slew controll only for tracking not for Goto.

Regards

[davidpretorius]

i will keep you posted on how i go motorizing my dob. el is a long way down the track with the computer controlled focuser. It will be controlled at this stage by a laptop and powered by 12 volt battery

Current options http://www.roundtableplatforms.com/default.php made to order from the states. Costs $500 american, but manual dec control & manual focuser.

Mike Salway has one!

Worst case scenario ie buying all new parts from RS without any trade discounts etc ( i sourced the 3 stepper motors for free from 3 old 5 1/4" disk drives)

Area Description Qty Price Total
Tracking Stepper Motor 1.8 degree 2 $80.00 $160.00
Tracking Gear reducer 2 $165.00 $330.00
Tracking Bearings 4 $12.00 $48.00
Tracking 560mm diameter x 1mm Alu plate 1 $30.00 $30.00
Tracking Extras 1 $50.00 $50.00
Subtotal $618.00
Focuser Stepper Motor 1.8 degree 1 $80.00 $80.00
Focuser Extras 1 $50.00 $50.00
Subtotal $130.00
For Both Controller for 3 steppers 1 $85.00 $85.00
Subtotal $85.00
Total $833.00
Sell inc gst $900.00

EQ6 mounts are over $1000 and to motorize, you would have to start adding more to that price?

Like I say, i will see how i go, could be a complete flop. I would love to get going for snake valley, to get feedback.

[netwolf]

david, it was my understanding from your post that your building an Alt-Az goto system which tracks in Alt-Az. This system would still need a Wedge and then your program would need to be converted to use your Alt-Az motors as RA-Dec. This is similar to Mel Bartel's system and the Meade Autostar Fork system. It will be intresting to see what you come up with and the total cost. Good luck.

Tom Hole http://www.tomhole.com/EQ%20Platform.htm
has built a EQ Platform using a Hurst Bipolar Stepper motor.
The Hurst 300:1 0.025 degree per step motor used on EQ platforms in the USA is available online for $15 US. See link bellow (I hope its ok to post this link)

http://www.electronicsurplus.com/com...oduct_id=71092

Hurst Specs are here for this series of motors.
http://www.electrosales.com/hurst/lsg35_geared.htm

I wonder if these are used in any old equipment, we could rip them out of these. But $15 US is not too bad.

And the controller is for $29 US see link.
http://electronickits.com/kit/complete/motor/ck1404.htm

[davidpretorius]

to start with, yes in alt/az. the maths looks fine to convert the spherical co-ordinates systems between long / lat, RA / DEC, ALT/ AZ. Being software driven, as long as the motor can be precise and smooth enough, then i can't see a problem of adapting to any platform. basic dob mount or EQ dob mount. Just tell the software what you have and it can track in RA and drive the DEC etc or drive in ALT / AZ.

Point it at a star or two or three, to calibrate and then off you go

As an extra , i want to add field rotation, so that the system knows where it is and then it slowly slowly adjusts for field rotation.

I could just as well be speaking out my @@@, but I believe it should be able to be done.

[netwolf]

David, you dont need to wory about field rotation as such. If you put a Wedge like the ones on the Fork mounted goto system under you dob set for your latitude. Then switch your system to RA-Dec, the RA-DEC program will need to slew and track. I think...

[davidpretorius]

mate,

top find on the combined stepper / reducer, well there is $400 saved straightaway!!!!!.

i am sure once all prototypes are done, then M Pinner (structural), EL (electronics), your fine self, myself (programming) et al (asimov with a big dose of left field, devils advocate, did ya think about this scenario boys?) can come up with a cost effective range.

Computer driven mounts and focuser controls
1. eq platform mount only: $250
2. dob mount - alt/az adapters for tracking and focussing: $450
3. combined eq mount with ra / dec drivers and focussing: $600

based upon sourcing that geared stepper for US$15 ea

[davidpretorius]

M pinner is looking at wedges to be made here, so we can source those well.

[netwolf]

Alt-Az tracking apart from field rotation also does not smoothly track stars, its steped because both Alt and Az need to change. Where as with an RA-DEC, once you are on the object only your RA needs to counter the earths rotation. With minor tuning of DEC.
This is a good demo.
http://science.howstuffworks.com/telescope5.htm

It has also been reccomended to me by my mates that i might look at an Alt-Az motorisation and then add wedge like device for polar alignment. Specifically the Mel Bartel system. And being in IT i am sure i can locate a few old Floppy drives.

[netwolf]

Dave, here is your design in action on a EQ Wedge
http://www.haven.k12.pa.us/orfft/wedge.html

Note the steep angle the DOB must sit on. Where as in a EQ Platform/Table the Dob is seted more parallel to the ground. why is this so, well you need to look at the following link to see the theory its got me warped.

http://www.atmsite.org/contrib/Shaw/platform/

[davidpretorius]

yes, the wedge gets the angle very steep, i would have to make at 47% here.

i will check what angle eq platform Mike Salway's is at?

[davidpretorius]

this is good link too

http://homepage.ntlworld.com/molyned...l_platform.htm

yes eq mount preferred option, the wedge, may be cheaper and also an option.

i will talk with M Pinner

[ballaratdragons (Ken)]

Mick Pinner might be thinking of making EQ Platforms. (Just a guess)

He has started another thread asking the Diameter of all our Dobbie bases!!

[davidpretorius]

Ken, that is for the scope buggy for the dobs. We had a chat on he phone last saturday, and i reckon he is not too far away from getting this dob buggy up and running.

I will convince him to add the motorized eq mount with focusser as well!!!

[netwolf]

Dave, have you considered using servo motors at all? I have seen a article on the web about a Servo Focuser using two Servo motors, one acting as a generator (moved by hand) that suplies current for the other to turn the focuser. Somethign similar could be used to gear the generator to the Alt or Az motor. I am assuming here that the field rotation will be in some way propertional to either the Alt or Az motion or both.

[davidpretorius]

i spose i am a stickler for stepper for precise movement without the need for decoders for feedback etc, but that is not to say, i will disregard them!

[iceman (Mike)]

Would be great if someone local could produce these, I dont' know of anyone except Mick Pinner who has the expertise and contacts, but from my understand he's more in the metal field, rather than the wood field.

So it depends what they're made out of, how heavy they are etc. They have to be solid, but transportable and not too heavy. They have to be stable and track smoothly, because people will want to use them for photography.

The good thing about the EQ platform as opposed to the alt/az driven method for astrophotography, is the elimination of field rotation. Alt/az astrophotography is certainly do-able (just check out all the LX200 fork mount astrophotography) but ultimately the serious guys end up getting a wedge.

As for your other requirements:

1. Dual Axis to track in RA and make adjustments in DEC if required.
2. Method to allow simple polar alignment.
3. Handle 6" - 12" Dob's. Perhaps even 16".
4. Adjustable Latidude.
5. Option for Intelegent DSC's (Argo Navis) to provide Slew control.
Any other requirements people can think of?

1 and 5 are really just nices to have in my opinion, and they're likely to just push the price up. You'll certainly want to be able to provide a no-frills option to keep the price down for those that want tracking on a budget.

If the price starts getting up around $1000, people will just buy an EQ6. The main consideration should be budget, and you should be targetting to keep the price around or under AU$500.

Just my thoughts..

[slice of heaven]

Under $500 makes for an affordable option for the larger scopes. But I ,myself would prefer dual axis drives.
The EQ platform would be more user friendly than the EQ6 on a tripod for visual viewing.
They dont need to be made of wood as there is several aluminium brands available.
http://www.equatorialplatforms.com/alumplt.html

[davidpretorius]

i am very keen to try and get made a few versions at around the $400 - $600 in aluminium.

i will talk with the local engineering shop and lathe boys