ASA 10 and DDM60 PID numbers

[MarkS]

I'm interested to know typical PID numbers for this combination. I know it depends to some extent on the camera, but I'd like to get some guidance on this. I'm using a STT8300M with standard filter wheel.

 

Any input welcome

 

Mark

[D.Weinzinger]

Dear Mark,

 

Why you not use the Autotunning option?

 

Best regards,

Dietmar

[MarkS]

Dear Dietmar,

 

I have used both manual and Autotuning. The RA sidereal numbers Autotuning gives are D 1575, I 100000, P 15.

But it does depend to some degree on what the initial values are set before Autotune is done.

So I am interested in what others may have set fo r similar equipment loads.

 

Regards,

Mark

[DaveK]

I have an ASA N10 Astrograph with an OK3 focuser and an FLI ML8300 & FLI CFW2-7 on a DDM85X-SL and my settings are the following:

 

RA DIP= 2130, 72000 13.5 Noise Filter Off

DE DIP= 2100, 71000 13.8 Noise Filter On

 

Polar alignment is accurate to 0.15' RA and 0.2' DE.

 

My tuning on both axis is less than 0.11 peak to peak in sidereal.

 

I have a 40 star pointing model with 20 stars on each side of the mount.

 

This allows me to image with MLPT for 20 minutes unguided operation with nice round stars.

 

Please note this is a portable operation. I have nice round markings on my driveway for the Losmandy Titan Tripod feet and I setup the mount for each imaging session, which lasts about 10 days. Each time I set up the system, the tripod markings find my polar alignment with about + or - 20 arc minutes, well within the FOV of my ML8300.

 

Once setup, I run the balance routines in both HomeFind and Polar positions, then I always check the tuning and make tiny adjustments if necessary to obtain the 0.11 peak to peak error. No more than a few clicks of increment/decrement are necessary on the D or I settings. I always stick P to I.

 

I save my tuning sessions for EVERY combinataion of telescope, camera and accessories. I have for example, one for ASA-ML8300-CFW2-7 and another for ASA-ML8300-CFW2-7-LuntSolarScope when I have the Lunt solarscope mounted on top of the ASA N10 for daytime use. I also have a very different tuning setup for my RCOS 12.5" astrograph with an FLI PL16803 & CL1-10 Filter Wheel.

 

I hope this information helps you to find a good starting position. Good luck finding your optimal tuning parameters.

[MarkS]

Hi Dave,

 

Your information is very helpful. I have found that Autotune gives quite variable results, so I guess it is a matter of fine tuning manually to get to the levels of tracking accuracy you have.

 

Regards,

Mark

[DaveK]

Mark,

 

I am glad the information I have provide helps. One more thing to think about. When you have a very good set of DIP parameters, the mount should almost be silent. In fact, mine is completely silent in DEC and in RA it makes a very low whining noise, like a mini jet engine ramping up in speed when it takes off, the same tone during slew and then a winding down sound as it comes to a halt. This is a very subtle and quiet sound, but when you hear it, you will know you mount is tuned perfectly.

 

When the mount is at rest there should be no physical oscillations of the OTA or counter weight shaft. If you have any check to ensure the noise filter is not enabled on the RA. Likely you will need the noise filter enabled on the DEC axis.

 

Let me know your results.

[MarkS]

Thanks again, Dave.

 

The weather here has been atrocious of late, but I did get the chance to re-balance, re-tune and then do a quick test under the stars.

 

First, I reset Autoslew to factory settings to make sure of a fresh start.

 

After balancing as best I could  - I can't get it perfect everywhere - I ran Autotune, and got the following: RA DIP 1575, 83835, 18.6; DE DIP 1575, 126644, 28.  Noise filter on in both axes.

 

I then tweaked these numbers manually, and found a better result for DE at 2130, 114000, 25.2 Noise Filter on. Slewing and tracking both virtually silent.

 

Both axes now showed about 0.15 arcsec peak to peak. Using these numbers, I set up under the stars (my set-up is also portable).

 

The weather was very patchy, so I just did a quick 3 position same DE routine to get PA to 1.6 arcmin RA and 9.1 arcmin DE errors. With only the 3 position config loaded, I then ran an MLPT track for a 100 minutes and shot some 5 minute frames of of NGC6752.

 

Registration errors according to Pixinsight between the worst two frames (approx 70minutes apart) was 1.3 pixels.

 

There is more tuning to do and a better PA would surely improve things further, but these results look pretty good to me.

 

Mark

[Gerald]

Hello everybody,

 

If one have enough time to invest (balance, (auto)tuning, polar align, pointing file, this mount is tracking perfect. But believe it or not - the last time at comet imaging I was under extreme time pressure. I assembled the mount, made a roughly balance by hand/no motortuning,  pointed with the laser to Polaris, moved to the comet (8° altitude!), started a local tracking - send it to autoslew - and all the images have been perfectly tracked :_)  an impressive performance under these circumstances!

 

best regards

 

Gerald