Setting up the Moonlite DRO rotator/focuser for remote automation

This is a brief tutorial on setting up the Moonlite DRO stepper focuser/rotator for successful remote and automated operation. The main focus is on rotator set-up.Note the difference between remote “operation” and “automation”. You can obviously control the focuser and rotator remotely through your PC by using Moonlite’s NON ASCOM software, but you will have to be awake to do that! Now that Moonlite has produced a new high res stepper system that is fully ASCOM compliant, I suggest that you take full advantage of that and get some sleep!

Here is how to do that!

REQUIRED before starting:

1) ASCOM platform fully installed

2) ASCOM compliant drivers for the Moonlite hardware

3) Moonlite DRO stepper focuser installed and fully operational (requires properly configuring your USB port- see link above)

4) A telescope/mount/camera system that can be operated remotely including pointing, tracking, focusing ,plate solving and taking images. Some of these functions do not necessarily have to be ASCOM compliant but it will depend on your specific automation program.

5) An application that can control the Moonlite rotator that is ASCOM compliant (*this ONLY applies to the case of automated operation). Generally this will be an automation program such as CCD Autopilot, ACP, CCD Commander etc.

RECOMMENDED before starting:

1) FocusMax for focusing. This should be installed and tested. You can use any ASCOM compliant focus program you wish but FocusMax is very well supported, has been around for quite some time and works well with this system. The documentation is extensive and can be found on the Moonlite site via the link above. The current version of FocusMax is 3.8 and is found here:

2) A contemporary image automation program such as listed above. Most will allow for up to 60 day trials. I personally am using CCD Autopilot because all of the software I have been using for years is fully supported by this program. This will be very different for different systems and users.

Hardware set up, configuration and considerations:

The Moonlite High Res stepper rotator system is configured to work in tandem through a single controller and a single COM port. It is important that you follow the directions on the site for successful installation of the drivers and configuration of the COM port. Because you only have 1 port for both focuser and rotator you have to operate both functions in the ASCOM platform or not. You can’t do one function one way and the other a different way.

Once your drivers are installed and you install and set up FocusMax, when you go to the “system tab” you will be prompted to set up your focuser properties in the ASCOM driver. These steps are extensively covered in the tutorial on the Moonlite download page link above and on their website.

For rotator installation, the hardware instructions that come with the equipment are very clear and straightforward. The motor is secured to the upper flange with 2 supplied bolts. You can adjust rough tension in the belt by positioning the motor slightly upward away from the flange in the slots but most of the tension will be accomplished using the belt tensioner lever (see below). For this reason I would say it’s not critical where in the slots the bolts are tightened down as long as the motor is square with the flange (like the focuser).

The controller allows for connections with the 2 cables to dual ports, one from the focuser and one from the rotator. These are labeled as “motor 1” and “motor 2”. It doesn’t matter which one you use for what but please make sure the numbers match the driver numbers (see below). With both rotator and focuser connected to the controller, when you turn on the controller you will see the step numbers adjacent to each device. The step numbers for the focuser generally reflect the near focus position if you have been using your autofocus fairly routinely. The step numbers for the rotator generally are not representative of any specific point if you are using it in the ASCOM mode. Don’t worry about this. Your automation program will take care of figuring out how many steps correspond to how many degrees..with amazing precision! Trust me on this!

For initial adjustment of the belt tension I suggest starting with the configuration shown in the image below where both “limbs” of the belt are roughly parallel. Once you adjust it you should check to make sure you can’t manually rotate the camera with a GENTLE toggle back and forth (emphasis on gentle!). If you can it’s most likely too loose. The next thing obviously is to test the motor by using the up and down arrow buttons on the controller making sure it rotates in 2 directions (again remember which motor goes to the rotator and which controls the focuser!). If there is a delay of more than a couple seconds where there is no movement at all it could mean the belt is actually too tight. Be advised though the dual port controller will start at a very low slow rate when the buttons are first pushed. It is so slow you may not see movement. But the rate increases greatly once the buttons are held in for more then 3 seconds.

It is designed to ramp up slowly for users that are making fine adjustments using the controller buttons instead of software— if needed.
Make sure it sits square on the flange!

Make sure it sits square on the flange!

New Moonlite High Res stepper focuser/rotator fully installed

This is the belt tensioner lever which is used to adjust the tension. The current configuration is working perfectly for this system

This is the belt tensioner lever which is used to adjust the tension. The current configuration is working perfectly for this system

Both rotator and focuser are connected. In this system the rotator is Motor 1. Again don't worry about the step count for the rotator.

Both rotator and focuser are connected. In this system the rotator is Motor 1. Again don’t worry about the step count for the rotator.

Both rotator and controller connected. be sure to remember which one goes to which motor!

Both rotator and controller connected. Be sure to remember which one goes to which motor!

Software set up and considerations:

Now that the hardware is installed we are ready to embark on our first fully automated session! Once you have chosen your automation application, you will have to configure it to your system’s specs. Again this will be different for different programs but the same basic principles apply in the sense that the program has to be able to control the various operations including obviously rotation of the camera! There should be a section in the program that enables you to test that. (see below)

At some point in the set up or initialization phase of your automation program, you will be asked to select the type of rotator system you have . In CCD Autopilot as an example, you enter the software components of your system and under “Rotator” there is a drop down which includes “ASCOM”. In their documentation (CCD Autopilot) they instruct you also to check “change driver” if you are using an unlisted ASCOM compliant rotator (see below). When you click on “link to software”, the ASCOM chooser will present itself and enable you to configure the Moonlite DRO rotator driver. For the case of the CSL 2.5″ hardware, the correct settings are shown. Once you do this and click OK, that’s it! Your automation software (CCD Autopilot, etc.) will do the rest. Now once you have linked to your software and set up the driver correctly, be sure to test the rotator function independently in the automation program as shown below.

Make sure your automation program can control your rotator!

Make sure your automation program can control your rotator!

Your program will ask for your rotator specs. This is the example described above for CCD Autopilot

Your program will ask for your rotator specs. This is the example described above for CCD Autopilot

When you enter your rotator specs, the ASCOM chooser will appear and enable you to choose the Moonlite DRO rotator driver

When you enter your rotator specs, the ASCOM chooser will appear and enable you to choose the Moonlite DRO rotator driver. When you select that, the properties button appears which you then need to click!



Select the specific rotator type. In this case we are using 2.5″.**Also this is the time to select the controller motor you are using for the rotator! You should see at least 1 of each in the chooser.   Leave “set position” clear. Note the “reverse” box which you should start off as unchecked and then go ahead and check it if your program tells you to reverse the rotator direction.


Leave speed at 250! This does NOT need to be adjusted. Note the “steps per degree”. This is preset in the factory and is already calibrated. For the 2.5″ this number should read 115.83

Now we are ready for our imaging session!

A fully automated meridian flip!

Here are some common troubleshooting tips:

1) Initialization errors in your automation program (initialization is the process where the automation program learns the features of your system  e.g. hardware and software by going through the various operational steps i.e. focusing, plate solving, rotating the camera etc): most commonly it will tell you that your rotator direction needs to be reversed. Simple! Just check the “reverse” box in the driver set up page (see above). If you get a combined error such as plate solving and/or rotator control issues you will need to go back to the control section in your program and make sure the individual functions can be controlled. If you are able to control your rotator and also plate solve independently of each other but you still get the error, then possibly the belt is too tight but more likely it’s a plate solve problem.

2) You can control the rotator with the controller buttons but not with the automation program. Most likely the belt is too tight. Make sure there is no delay in rotation when you use the buttons on the controller. If there is no delay and you still can’t control the rotator with the software, make sure the drivers are installed and configured properly for your rotator. (See above). If you feel everything is in order and the program still will not operate the rotator, you should contact support for your automation program.

3) Operational errors in rotation. Be sure to check the imaging log of your session. If you see something like “rotational error not corrected” or similar, then your rotator belt is too loose. Also check the set screws on the flanges above and below the rotator and make sure they are tight (see the assembly instructions from Moonlite for the location of the flange set screws)

Congratulations on your automation success! Sleep tight!

Dr Dave

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