GeorgeCarey

I tried the mount out yesterday and again today. No weird behavour with the currents seen. I ran it today for over 3 hours - no problems. Many thanks to ASA for sorting this out.

Which is, in English: In terms of precision will hardly be differences, which are the incremental already very good. In the software there might be in the future with the Absolute more options. At the start of the new software, there will be no differences. Currently, our developers work in testing with mounts with incremental encoders. Translated by Google

The mount is now back from ASA and on the pier, so it is time to get the final stage of balancing the telescope finished. This is to check the lateral balance: The scope tube has been marked to show the position that the tube rings should be in. It should be possible to reproduce this position if the scope has to be detached from the mount and replaced.

The mount is back, but I have not yet put it into the observatory. I have a bit of a back problem so will need a friend to help lift it.

Camera now back on telescope. I decided the suspension cradle was inadequate, because it was not easy to check that the cable was perfectly centred on the telescope plate. This version uses a rectangular bar: Result seems very good, The scope is well balanced:

This is the method: http://www.astrooptik.com/asa/EncoderResOptimizingDDM60.pdf I think you will need one of the older versions of Autoslew, but maybe Autoslew can tell what type of encoders you have.

Thank you ASA. Are there any plans to change the hardware and firmware of the DDM mounts?

The first DDM60 mounts did not have absolute encoders. The encoders fitted had to be calibrated by the user. This did not work very well so now they all have absolute encoders.

News from Austria - the mount is on its way back!

I am simply saying that I don't think we should speculate on the relationship between ASA and Philip. This could start damaging rumours. I would prefer to wait for a response from ASA.

We are now getting into the realms of pure speculation.

I have just received an email from ASA. The mount is due to be shipped back to me in a day or two. The mount was disassembled, and then rebuilt with a new set of bearings. Plenty of new grease was applied and also a new wiring loom was fitted. It has been tested and ASA sent me a couple of logfiles. The currents in both motors seem to be behaving well. I am eager to try it out when it gets home. I hope the couriers handle it carefully! Many thanks to ASA!

John, no stones coming from my direction. I would also like to see more technical discussion. However, I think this needs to have an input from ASA. There are still many facets of the DDM mounts and Autoslew that puzzle me, even though I have had my DDM60 for over 5 years. Occasionally I have asked questions on the forum and have had a few member responses, but really I need definitive answers from ASA. I enjoy the images posted by members - keep them coming! George

Second phase of the balancing. I made a template to suspend the camera/focuser, and added a lead counterweight to the balance arm. The balance was checked by seeing if the steel cable was at 90 degrees to horizontal lines on the camera. This gif shows the perpendicularity: The only thing that could upset the radial balance now is asymmetry in the tube rings, and the placement of camera and focuser cables.

Email today from ASA. The mount has been disassembled, put back together and is in the testing phase. No indication yet of what was wrong with it. George

Hi Bernard, That would work, but I like to have the vanes of the secondary support oriented N,S,E and W. I could rotate the camera to make North upwards in the images, but then the diffraction spikes would be at a strange angle. George

First try at balancing the system. I bolted an aluminium bar to the side of the camera as seen here: It seems to be about the right weight to balance the scope. Obviously this is an awkward solution. However, it is easy to calculate what weight is needed at the end of a shorter bar.

Hello Georg, There is a 'stopper' that prevents 360 degrees rotation on both axes. Some mounts have the cabling internally and this will prevent them getting twisted. Welcome to the DDM users club! George

I think the Autoslew balancing tool is great, but I am not convinced it will allow you to determine radial balance. My DEC axis always feels harder to rotate in one direction than the other. I tried an experiment by putting the counterweight shaft to the East and pointing the scope vertically. I then used a counterweight near the camera to give perfect balance according to the Autoslew tool. With the scope pointing upwards the main component would be radial balance. When I moved the counterweight shaft to the West, I got different results. The pre tensioned bearings seem very tight, and friction possibly overwhelms fine balance attempts. What would settle the issue is if I could get hold of a perfectly symmetrical tube with no cameras/focusers. That would be the best way to check the balancing tool.

We all know how important it is to get the scope properly balanced with a DDM mount. Radial balance is difficult to achieve, so while my mount is back with ASA I have made a rig to assist in balancing. The whole system, scope, camera, focuser, telescope plate etc, is suspended on a thin steel cable. Obviously great care is taken to make sure the cable will not come loose or snap! There is a white card placed behind the cable with a straight line drawn on it. I took care to ensure that the line was perpendicular to the telescope plate. This is the setup: The first trial showed promise. The cable did not snap! (The scope was only lifted a centimetre.) The cable is not quite parallel to the marked line, suggesting that the there is a small counterweight needed near the camera. The success of this experiment relies on the cable being accurately positioned over the centre of the telescope plate. An error of a millimetre will produce an inaccurate result. I will spend the next few days thinking up a way to accurately assess the cable position. What do people think? Is this a sensible way to measure balance? I am also considering taking the focuser/camera assembly off the scope tube and making a separate balance check with it alone. George

The mount is going back to Austria

Thanks Gerald. Martin has replied to my request.

I ran a test with a 12V car battery. Same problem, so we can rule out power supply problems. Over to ASA.

Thanks. I got an email from ASA today.

Thanks everyone for your help. I have contacted ASA and am waiting to hear from them. George