East heavy balancing on remote mount

[Magnus_e]

Hi.

With my recently built observatory I have reached upon a question. As the title explains is there possible to do EHB on a remote mount?

I wont claim to be a seasoned imager, but until now I have had two marks on my counterweight shaft to show my how much I should move the weight after meridian to always keep the gears lifting. This has to my opinion been beneficial in continuing good guiding after the flip, but I will not be able to do this remotely.

However I remember seeing a while back someone trying to fix this with some cleverly mounted rubber bands, to get the slop out. I.e. balancing the mount perfectly and letting the elastics take out the slop.

 

Is this something I should consider? Are there any other options?

Do not now what others do. What's the common way in balancing a remote mount?

 

Please dont be shy in making suggestions

Magnus.

[spaceboy]

While not directly related to your question it may be food for thought. I'm no imager but I know from using heavy eyepieces (not far off the weight of a small DSLR) that the orientation of the focuser can play a part in balancing. There is a video on YouTube that emphasize how just the orientation plays it's part. I will try to find it and post a link.

[spaceboy]

 

 

Edited December 15, 2016 by spaceboy

[Magnus_e]

Hi. Did not realize that had so much effect. However I image with a refractor, so everything is aligned down the center.

Perhaps I should elaborate on what I mean.

The issue is not with the dec axis, but the ra.

As the the ra tracks and 'rotates' the scope and counterweight, then there will be issues with a perfect balance.

A slight breze can make the scope move slightly faster than the ra motor, catching up to the next 'tooth' in the gear and adding slop.

Then the ra motor catches up when the scope stops and the slop is removed.

This can make things 'notchy', and be a problem for guiding.

 

The fix is to balance the counterweight so that the east side is heaviest. So if the scope is on the east side then scope should be heaviest (after meridian), and the counterweight should be heaviest before the flip.

This causes the ra axis to always 'lean' against the gears, effectively making sure there at no slop in thee gears

 

It's carefully explained here @26min13sec

 

[ollypenrice]

If you are doing remote imaging I honestly think that you need a backlash free mount to start with - or you accept imaging up to the meridian flip (which might be well past the meridian) and then going back to a different rising target in the east. Unless you make some kind of moving weight, software controlled, I don't see any alternative.

Olly

[Magnus_e]

That sounds right. I could not figure out the geometry to use some external elastic to push and pull, if that makes sense.

I could make use of a linear servo that lover and rises a ~25g weight on the counterweight bar.

I use INDI and have already mad a driver for servo control (a automated duskcap) and could snoop on the telescope driver, to change the position after flip  

As you say, deciding on imaging before or after the meridian should work. I could do a manual re balancing if I change target for a project. I do visit the remote site quite often.

[andrew s]

Depending on the design of the mount you can quite simply apply a net torque in the direction of the RA drive by using a weight and pulley. You need a few turns of cord round a part of the RA axis, which turns with the drive, then over a small pulley with a weight on it. This can provide a fixed torque independent of the side of the meridian the mount is on.

It is simpler to do that describe!

Regards Andrew

[Magnus_e]

1 hour ago, andrew s said:

Depending on the design of the mount you can quite simply apply a net torque in the direction of the RA drive by using a weight and pulley. You need a few turns of cord round a part of the RA axis, which turns with the drive, then over a small pulley with a weight on it. This can provide a fixed torque independent of the side of the meridian the mount is on.

It is simpler to do that describe!

Regards Andrew

Thats a great tip Will check into how big of a weght I need. Should be able to test this very lo cost:)