Mesu 200 PointXP modeling

[dan_adi]

Hello,

For all the Mesu 200 mount users, I wrote a little tutorial regarding mount modeling. After a good feedback from Mr. Dan Gray and Mr. Steve Richards I decided to share it on the forum. Please feel free to add any suggestions or corrections as I'm just a beginner in this wonderful hobby 

Mesu_200_modeling.pdf

[Fellside]

Hi Dan,

Very interesting. Thank you for taking the time to do this.

Can I ask what load you have on your Mesu. I have about 35kg plus balance weights. I will soon be adding a second scope to this (9kg) I have never had to my knowledge any slip on the drive. I run all settings as supplied by Mesu. As you found balance can be done by feel along and I find it gives acceptable results. If you make any changes to you image train you will need to resemblance and in theory redo your mount model. 

I usually do a plate-solve sync and slew to the object.  Great Mount😀

Regards

Graham

 

[Star101]

Hi Dan,

Thank you for taking the time to create this PDF. You have put some very interesting bits of information in there. I will re read and check my Mesu settings to see if I can improve the guiding. Although I do not use modelling, I do use Plate Solving and have very few issues. However, there are some interesting pointers in there that I would like to try out. Every little bit helps. 

Thanks again.

[dan_adi]

1 hour ago, Fellside said:

Hi Dan,

Very interesting. Thank you for taking the time to do this.

Can I ask what load you have on your Mesu. I have about 35kg plus balance weights. I will soon be adding a second scope to this (9kg) I have never had to my knowledge any slip on the drive. I run all settings as supplied by Mesu. As you found balance can be done by feel along and I find it gives acceptable results. If you make any changes to you image train you will need to resemblance and in theory redo your mount model. 

I usually do a plate-solve sync and slew to the object.  Great Mount😀

Regards

Graham

 

Hello, I have a 12 ich SCT F8, Moravian CCD with FW, ONAG, Leo focuser, Asi 183 (for autoguiding), top plate, intel nuc, pegasus astro,  I think about 40 KG. And a 140 mm APM refractor which I haven’t mounted yet. You won’t notice the slip because it’s very small. Because the supervisory threshold default value is 10 degrees the scope encoders will never correct the position of the motor encoders because the disagrement between the 2 will never be that high. If you lower the supervisory threshold by the recomended setting in the sitech manual (2x resolution of the scope encoders e.g 4 arcminutes ) and not lower the accelaration accordantly you will see the effects of small cumulative slip and unbalance (the mount will start to oscilate , go into blicky mode and stop all movement). For me it was a learning experience. Offset init without cal inits (model) and platesolving works just fine, I totaly agree. I just think this mount could reach it’s maximum potential with a model.

[dan_adi]

56 minutes ago, Star101 said:

Hi Dan,

Thank you for taking the time to create this PDF. You have put some very interesting bits of information in there. I will re read and check my Mesu settings to see if I can improve the guiding. Although I do not use modelling, I do use Plate Solving and have very few issues. However, there are some interesting pointers in there that I would like to try out. Every little bit helps. 

Thanks again.

Hello, 

Sharing the information will make life easier for everybody. This is not an easy hobby, but very rewarding when you make something work  . THe model should make guiding even easier (in theory) but I have’t tested yet (bad weather, and I’m replacing my brick pier with a steel one). As soon as I can I will test guiding and even how much I can expose unguided with a model.

Have a nice evening

[Fellside]

Hi Dan.

Would it be possible to share some screen shots of your

Sitech Config page where you Reduce the acceleration.

Supervisory threshold page in Sitech.

Regards

Graham

[dan_adi]

Yes, tomorrow I will post an image, no problem.

[dan_adi]

the settings

[dan_adi]

Ignore mode when modeling, Polite mode when imaging 

[Fellside]

Hi Dan

Thank you for the screen shots.

I will be rearranging my rig soon, I will try out your method and settings. Hopefully I to will get a more accurate model.

Many thanks

Graham

Edited September 29, 2019 by Fellside

[dan_adi]

On 29/09/2019 at 20:34, Fellside said:

Hi Dan

Thank you for the screen shots.

I will be rearranging my rig soon, I will try out your method and settings. Hopefully I to will get a more accurate model.

Many thanks

Graham

Welcome. Hopefully next week I will install a new pier and the apm refractor on the mesu. I think with a refractor I will get consistent modeling results. As soon as I am up and running I will review the tutorial. 

[dan_adi]

On 29/09/2019 at 20:34, Fellside said:

Hi Dan

Thank you for the screen shots.

I will be rearranging my rig soon, I will try out your method and settings. Hopefully I to will get a more accurate model.

Many thanks

Graham

Hi , I have a new steel pier. I redid my polar alignment routine with the pole master and got below 1 arcmin error in phd guiding asistant. I did a model with 20 points and the total rms error was 20” and a polar alignment error of around 30”. I have constant results of 20 “ rms with my apm 140 mm refractor without eliminating any outliers. If I removed one outlier I was down to 13” arcsec rms value, witch is very good performance for the mount. From my trial and error experience the rigidity of the optical train is very important, along with balancing, time synchronization etc. that being  said I would not encourage mount modeling with reflectors that have movable mirrors. The last thing I will improve is focuser rigidity. For now I have the stock APM focuser. I will replace the stock focuser with my Optec Leo low profile focuser. It doesn’t have a rack and pinion mechanism therefore there will be no slip and it will have a better payload capacity. The challenge is to get the right dimensions for the spacers because the Leo has only 1cm travel but high resolution (0.08 microns per step). Regarding the influence of mount modeling on tracking, I only did one test. I use SkyGuard for full frame guiding. The guide graph was good but it’s to early to draw a conclusion. It will be hard to tell if the model affects the guiding performance, especially since I am just learning the software for full frame guiding. In december I will receive the adapters from preciseparts and if I got my distances right I will test again. There is a small slip in my stock focuser and also a small sag, so things can improve. If all goes well I will update the tutorial with new results and pictures. 

Edited November 14, 2019 by dan_adi