skywatcher heritage 130p slomo ALT control dobsonian mount :first prototype

[sockgoblin]

Spend a rainy Easter sunday in the shed.

Firstly credit where credit is due I found this idea here at dobs slo mo 

I have tried to adapt it to the much smaller 130p and it works but needs some tuning.

I have attached an arm made of plastic ( but could be anything stiff but does need a wide diameter at the telescope end.) between the base board support arm and the mount for the OTA.

and a turnbuckle between the arm and the base board. When the turnbuckle is spun one way it increases in length and reduces in length when spun the other way.

When the tensioner knob of the telescope is loosened the OTA moves freely and then when the knob is tightened (not so much that it absolutely freezes the scope) then it acts a a clutch and movements in the turnbuckle moves the telescope.

The blue ball is just a handle I attached ( which is actually too big and fouls on the body of the telescope so I will change it soon.)

Photos show the angle between open and closed ,I also taped a laser to the tube to see if I could hit a pencil mark on the shed roof with success.

Well it works in the shed , when we get some clear sky I will try it in anger.

AZ movement is next project

 

[sockgoblin]

the last photo shows a new position for the bottom connection of the turnbuckle. This position works much better as the forces now act on raising and lowering the arm ( before it was trying to push outwards.)

[happy-kat]

What is the range of angle movement on altitude  it looks like about 20-30 degrees in total?

Interesting concept.

[sockgoblin]

Not sure the size of angle, you can get the turnbuckles at allsorts of sizes and the length of the arm will also have an effect. I expect to slacken off the black knob and use the telrad to aim the scope, then to fine tune with this setup. When I get to the extent of the tweak then slacken off, re-aim and go again.

[sockgoblin]

Not as sure about this one . After lots of thoughts on making a Az slo motion adjustment for the 130p. They included variations on a screw system that would push and pull the bottom disc of the base board around, Ive ended up with a most rudementary solution. The problem is that the solution has to allow the board to spin easily when swinging from one quadrant of the sky to another but also to control nudge typ dobsonian movements.

So I have a plastic mecanno wheel with a tyre made of an rubber band, the wheel is glued to a slider.

When spinning large angles the wheel is just rested on top of the board and not used at all and when needed just placed against the edge of the board and can fine adjust the AZ movement.

I will need to try this one when I have my lazy susan bearing.

[happy-kat]

That looks promising.

[sockgoblin]

I have used my slo mo setup tonight and I am very pleased with it.

I used a 9mm plossl and a 2x Barlow to view Jupiter and I was able to tweak the alt view with very fine control. The only improvement I need to make it to make sure that the bolt which attachs to the arm fits well as there is about three turns required to change direction from up to down

Even my mecanno wheel does the job , but not as smoothly as my trusty turnbuckle.