Equatorial Wedge for Sky-Watcher 200P Dobsonion

[Dr Hamzonian]

Hi Guys/Gals,

So I have been thinking of doing this ever since I bought my Dobsonian. Basically, adding a 45 degree (~Ottawa lattiude) base that my dob can sit on, and point it North. Essentially converting my dob from alt-az to ra-dec. I haven't seen this before on the web, but a quick search on SGL confirms that it seems to have been attempted before in 2008 (of course, you guys seem to have done it all!), but with the pictures missing it wasn't very useful: http://stargazerslounge.com/topic/30202-how-to-equatorialize-a-dobsonian/

Having noticed that the SW 200P Dob is a popular one around here, I thought I would share my 1st iteration of my design. Hope the rest of the SW- DOB-MOB finds this useful!

[Dr Hamzonian]

Here it is on 1st light pointed to jupiter

[Pompey Monkey]

Ingenious.

But I am really not sure that dobsonian mounts (especially when made out of chipboard) are designed to take those kind of lateral stresses!

The balance looks a tad precarious too...

You seem to be handy with tools: have you considered an equatorial platform?* Here is a very good example, although there are many more on the 'net to look at: http://www.reinervogel.net/index_e.html?/Plattform/Plattform_e.html

* I am currently designing and building my own at the moment. I might eventually even start a thread on it! Might.

[Dr Hamzonian]

Thanks.

I wanted something that I could build without any power tools in a day. I literally used a hand saw, drill, and a plastic mitre box. I had the plywood cut to size at the hardware depot for free (Rona in Canada). It is actually really well balanced at all positions; I have added a piece of plywood at the bottom and threw a couple of bricks in there for extra stability. It is rock solid, more solid than a regular dob mount. The trick to all of this is the clamp, and the tight fitting holes around the rubber legs, very stable.

It is sooooo much easier tracking planets at high magnification with this. I plan on taking a video hand tracking Jupiter with this, and will post here. Haven't got a chance to image with the wedge, but I am hoping to tonight. I have got an idea to add slow motion control to make it even easier. I am not sure if there is extra stress on the azimuth bearing, the clamp shifts the weight back to the centre of the bearing through a line contact on the top disk (I can post pictures if you would like). I think the cheap single bolt through the middle type bearing is actually advantageous in this design. Either way, it won't be mounted permanently on there.

I have looked into eq platforms quite a bit, and then realized that this is easier, with actual full tracking capability as opposed to the hour or so that eq platforms give you. But I would love to follow your progress if you attempt a build (messege me if you do). Also, if you decide to give this wedge a shot, I would gladly help.

[Bizibilder]

That looks an interesting project.  The problem for the UK is that we are at around 51° - 59° N which would make such a device quite unstable!  Those few extra degrees make all the difference.

[Dr Hamzonian]

Yah, I lucked out with my lattitude. I am always suprised on how low Ottawa's lattitude is, given that it is the third coldest winter capital of the world.

Though I bet you could push it to 60degrees if you add a couple of 2x4s to the front (lower end) on either side, and add some weight to the base on the other end, that might solve the stabilty issue.

[urchin]

That's a nice neat build. Well done. I have a 250px and may well do something similar. How does the clamp assembly work I can't tell from the photos. I'm in the UK about 55 N. That should be less of a wedge (35 deg) as closer to the pole.

[Psychobilly]

Nice practical build

The other advantage of being at 45 deg latitude is you cant get the angles the wrong way around...

Peter...

[Dr Hamzonian]

Haha, yup!

I just rigged a slow motion control lever for the RA (formerly az). Will share once I improve it a bit. Should make planetary imaging with the dob a lot less of a pain........now to motorize it hmmmm....

[DOBGUYNORTHWEST]

How has the design held up for you? I'm looking at doing this myself as I have the same scope, any comments would be appreciated!