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How to : Point telescope to zenith?

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#1 LaCebra



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Posted 02 July 2017 - 08:20 PM


I do not speak English. Thus, you will read the continuation at your own risk. J


DDM85 standard + 12N: mars 2017 + QSI 683wsg


Every night…
1- I verify with a level the horizontality of the base of the mount, 4 independent measures.
2- I start AutoSlew Version
3- I verify my geographical position: Mount -> Location -> Latitude and longitude (with http://www.mapcoordinates.net/fr)

4- I verify the hour of the computer: http://www.horlogeparlante.com

5- I connect engines " Motor is ON ".

6- Balance Ok

7- PID sidereal ok J – PID slewing always very doubtful… L
8- I verify the values of "Park 1 Zenith" : Mount -> Park Positions -> Set new Parkpositions -> Zenith -> Az: 180 Alt: 90 – East -> Cancel

9- I click the icon " House 1 " (what's its habitual name ?)

10- I click the icon "White right arrow on green bottom" (what's its habitual name ?)

11- The telescope turns to the zenith. Almost… … …

12- The counterweight shaft is in the East.

13- The counterweight shaft is too much raised in east of 2° (14mm for 400mm measured)

14- The top of the tube is tilted to the south of 3 ° (20mm for 370mm)

15- This error is systematic, and very precise (absolute encoders - false here but reproducible !)

16- I take a photo such as.
17- I look in Stellarium where I am lost (near zenith).
18- The error measured from zenith by Stellarium is regularly 3° 40'

19- I center one of the stars in this picture.
20- I make Sync in Stellarium (Ctrl+3).

21- I slew to NGC4565. In the center of sensor J
22- The problem is solved until the next day.
23- I don't find the page of the documentation concerning this situation? :D

24- But… exists in Menus : Mount - > Set new homeposition - > Please confirm that the telescope up is synched and centred and you want to define has new Offset for the Home-Reference mark.

  • "Synched" with what?
  • "Centred" on what?
  • what is "Home-reference" ?
  • what's the goal of this?
  • I don't use this L

25- After several cycles Pointing File, and Polar Align (< 1 arcmin), imaging of 900s of NGC4565 show the beginning of the strain of stars. When everything goes well. It's very rare… Picture is here :


26- I have many other problems important to solve, after J

27- Thank you for your help.


La Cebra

Native tongue : French

Beginner : Spanish

Machine translation system : English :rolleyes: 


#2 lukepower



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Posted 03 July 2017 - 04:35 PM



what you need to do (and add in) your procedure is the following:

  • After you started the motors do a Homefind (Mount -> Homefind). 
  • After you successfully solved and sync'ed your mount, go and set the new reference position.

This two steps are important if you do not have absolute encoders. With the absolute encoders, only the second point has to be done.

And - what I would also check is if the parking position you expect to be the Zenith has the correct values: Mount -> Park Positions -> set new park positions


Best regards

Lukas Demetz
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL

#3 astrosirius



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Posted 04 July 2017 - 07:20 AM

Good Morning Fabrice


Please try to get in touch with me, I will try to help you in Spanish, as you know I am in Catalonia, so we have the same timetable.
Please call me and i will try to help to you as much as I can.


My cell phone is: 607.56.98.34 (directly call)


If you have teamviewer, I can enter in your computer and help you to understanding the correct procedure, I think it will be a great helpfull, I hope so.


Un abrazo amigo Fabrice!



#4 LaCebra



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Posted 08 July 2017 - 02:03 PM

Thank you Lukas.


I have made SetNewHomePosition.

Now, in the starting up, the counterweight and the tube are horizontal and vertical.


I would like to see a photo of the fixation of the absolute encoders on the mount.
To understand...


See you soon.

La Cebra

Native tongue : French

Beginner : Spanish

Machine translation system : English :rolleyes: 


#5 Waldemar



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Posted 08 July 2017 - 05:11 PM

I do not think ASA provides pictures of that, Fabrice...

Mount: DDM85 Standard 12V ; Telescopes: TEC140 + 140FF + Quad TCC ; Celestron RASA; TMB 92SS + 27TVPH Cameras: ZWO ASI 174MM cool; SBIG STF8300M; ATIK4120EX; TRIUS SX-36
Filters: Astronomik and Baader NB + RGB; Lunt double stack 75 mm unobstructed signature series + BF 3400; Dutch weather and light polluted skies.  

#6 LaCebra



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Posted 09 July 2017 - 04:39 PM

I also think of it. :D


But, if somebody opens a DDM85 mount one day...
It would be the moment of to know more about it! :o

Native tongue : French

Beginner : Spanish

Machine translation system : English :rolleyes: 


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