Dob Platform, cheap, cheap, cheap!

[Escortitis]

Hello People,

New to your forum, and big 'scopes. So i thought i would give you all a good chuckle by sharing some pics of a dob platform i'm knocking up. I spent all my money on a 12" lightbridge and some imaging gear, and while WA(iting) for it all to get here, i've got too much time on my hands.

Most of the stuff i used started its life as a motorised sat. dish mount, including the actuator. It is a 24v-36v Geosat jobby which has remarkable rigidity in its operation, i guess a prerequisite for moving 2m dishs' in the home of the Freo doctor.

Really simple concept, used longest 'practical' levers and the 12" of actuator travel to get a total angle travel of 15 degrees. The electronics hanging off the back, provide crude stepping. A PWM gives motor step 'speed' and the other bit is just a timer, a 0.1sec impulse every 1.5sec's. Roughly gives me 2300 steps in the hour.

When the scope arrives, i can fit a platform to the square tube then need only minimal fixing of the standard lightbridge mount, just a lift on, lift off setup.

I hope that this 'thing' will be good enough for grabbing AVI's, and the freedom of being able to wait for the best seeing while 'setup'.(for that hour anyway) It resets in about a minute and a half.

I would like to recommend the crazy emotion, or the little fella rolling around laughing!

[ving (David)]

call me thick but i dont see how it works

welcome aboard

[Escortitis]

Maybe these shots will help. Just a platform at 30 degrees which you plonk your telescope on.

Tanks mate.

[iceman (Mike)]

Hi there to IIS!

A very interesting platform! I can see that it would work.. Without being curved, is it going to introduce field rotation?

I can see that is will give some level of tracking but I'm not sure it would be accurate enough for high-resolution planetary imaging.. certainly should be ok for low-res stuff like wide views of the moon.

I look forward to seeing it with the LB on top and hearing reports of its performance!

[ving (David)]

ah... ok gottcha

[netwolf]

If I am not mistaken Mike, there is a Curve on it. Not bad. Not bad at all.
The arm on which the pice of wood (base of rocker box) is resting is fixed on one side (being moved by the actuator above). And from what I can make out on the other side its fixed on a bearing that will let it turn.

I would suggest you need to such arms or a frame of some sort on top of it to hold the Dob base. Note sure you could rest you scope on this one arm safely.

Regards
Fahim

[Escortitis]

Thanks guys for the welcome and feedback.

The curve/arc should be ok, my mentors (my boss, and workmate) for this project seem to think the geometry of this mount should be similar to that of a normal EQ mount. Don't have much more to go on but, Fahims' comments are encouraging.

Your correct with its movement Fahim, two 12.5mm self-centering bearings keep it smooth with the expected 30 odd kgs. Yeah, 30 degrees doesn't sound like much but......! Need to wait for the base before going further with how i will mount it. It will be a frame thought, just for ease.

Learning lots going back in old threads, Great site.

George.

[Escortitis]

Back again,

Got the electronics sorted out and have managed to get 9000 steps over 15 degrees. Reset is 45 secs, and the electronics give me fully adjustable 'distance per step' but the timing pulse is fixed to 2.5 per/sec (not smart enough for that). The speed controller needs cooling at those figures, and quite abit at that!! (maybe lacking some smarts there too!)

So now i have a eq platform of sorts, but no scope. Never fear, i took the lens off a V-gear ccd and stuffed it up an old 135mm Minolta film camera lens. Sat that on the trusty block of foam (reads camera mount), found some stars and.........................spent a long time getting focal lengths right.

I think the area is top part of M42, i took 240 secs at normal exposure using K3ccd3, put it into Registax and got what you see below. I was out of focus, but it was best I could get. The mount tracked really well. There was a hot pixel near a star and it only moved NW about 2 'star lengths' in the 4 Min's.
not perfect for imaging but better than i had expected, great for just looking.

Anyway, its keeping me busy while I'm WAiting.

Cheers Guys,

George