Cogs and handles tracking.

[NIGHTBOY]

Has anyone ever tried making their scope track by using cogs and turning handles?? Would be great on a dobsonian.

[1parsec]

Has anyone ever tried making their scope track by using cogs and turning handles?? Would be great on a dobsonian.

There is a guy at our astro society who has done this using a couple of v-belts and pulleys.

He's placed the pivot 2/3 up the tube so the eyepiece stays at a reasonable height even at low elevations.

The scope has to balanced in elevation using a small gas strut which works very well.

It's very comfortable to use    I'll ask him if he has a photo of it...

[brantuk]

The SW EQ5 mounts (and a few other's) come with slow mo cables/knobs for manual tracking.

[nytecam]

Has anyone ever tried making their scope track by using cogs and turning handles?? Would be great on a dobsonian.

Heard of a Crawford Dobsonian?  Here's one I did earlier   It uses a Declination Clamp [DC] in the form of an adjustable rod [in pic it's a taut line of thread !] on the centre of the scope's optical axis beneath the scope flat and is anchored at the other end to the ground-board foot as shown.  An imaginary line from the anchor point through the centre of the scope's horizontal axis forms a polar axis pointing at Polaris. 

If correctly set-up on site then just a single movement of the eyepiece westwards keeps the object constantly in view as it arc across the sky.  This could be done by slow rotation of the vertical axis of the ground-board. For a new object at a different Declination then the length of the DC must be adjusted. Sounds complicated but is very simple once you get the hang of it.   My old article @ http://home.freeuk.com/m.gavin/crawford.htm explains more.  Worth a punt !    

[NIGHTBOY]

Wow that's fantastic! Looks like a spud launcher I made once

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This is the hand driven scope my friend built some years ago which is a constant height eyepiece design. You simply walk around the base, so no stooping or stretching on tippy toes. it's great for a comfortable observing session and also perfect for public star parties with the adjustable ep height. 

His comments and description is below.

The tower is one square box tube sliding over another.

In the photos you can just see a gas strut sticking up. The whole of the weight of the scope is borne by this. The gas strut fixes under the top horizontal board that holds the black axle.

The gas strut is stronger than the weight of the telescope, and so the telescope tends to sit high, for use by a tall person.

For use by a small person, the black wheel is turned. This has a 16mm dia steel rod as its shaft, and to this is fixed a long length of string. The string goes from the rod, down through the scope to the base of the telescope.

Winding the black rod, winds in the string, and winds the telescope down.

A hand brake with pawl is needed to stop the telescope popping up again.

The main horizontal bearing at eyepiece height is the thread of a flange. The telescope flange rotates on the threads by 90 degs. The threads keep the telescope in place. A bit of grease is needed on the threads. The pipe is fixed. There is a bit of slack in the bearing which is removed by the force from the gas strut. There is no sloppiness in the bearing.

The azimuth bearing is made from ball bearings. The running surfaces are 2mm mild steel sheets screwed top and bottom to slabs of kitchen work top. The retainer for the balls is a round piece of corrugated cardboard. I marked out the position of the holes around the perimeter, and then poked my pencil through the cardboard to make the holes. The ball bearings fit snuggly into the cardboard.

This bearing is far superior to the normal Dobson bearing using ptfe tabs. It has no friction or ‘sticktion’ and can take the weight of a person standing on it.

The telescope has lot more weight than a normal mount, but still I can move it around my house easily. It has a pair of wheels which tuck away when not in used.

The telescope lives in a corner of my garage, and I can wheel it out ready for use in a couple of minutes.

The optics are Newtonian 6 inch F8.